Arabidopsis thaliana YUC1 reduced fluoranthene accumulation by modulating IAA content and antioxidant enzyme activities.

Indole-3-acetic acid (IAA) can regulate plant growth and thus modulate the accumulation of polycyclic aromatic hydrocarbons (PAHs). However, the effect of endogenous IAA on PAHs accumulation and its influencing factors remains unclear. To unravel this, two different IAA expression genotypes of Arabidopsis thaliana, i.e., IAA-underproducing yucca1D [YUC1] mutant and wild type [WT]) were selected and treated with different fluoranthene (Flu) concentrations (0 mg/L [CK], 5 mg/L [Flu5], and 20 mg/L [Flu20]) to reveal the impact mechanism of endogenous IAA on Flu uptake by plants. The results indicated that under Flu5 treatment, the bioconcentration factors (BCF) and translocation factors (TF) of Flu in WT were 41.4 % and 14.3 % higher than those in YUC1. Similarly, under Flu20 treatment, the BCF and TF of Flu in WT were also 42.2 % and 8.2 % higher than those in YUC1. In addition, the BCF and TF were 72.5 % and 35.8 % higher under Flu5 treatment compared to Flu20 treatment for WT, and 73.4 % and 28.6 % higher respectively for YUC1. Moreover, WT exhibited higher plant growth (biomass, root morphology indicators [root length, root area and number of tips]) and IAA content compared to YUC1 under identical Flu treatments. Plant growth and IAA content declined with the increase of Flu concentration in both YUC1 and WT leaves compared with CK treatment. Conversely, in WT roots, root biomass and morphology indicators promoted followed by a decrease as the concentration of Flu increased. Additionally, the antioxidant enzyme activities (SOD, POD, and CAT) of WT were 11.1 %, 16.7 %, and 28.9 % higher than those of YUC1 under Flu5 treatment, and 13.6 %, 12.9 %, and 26.5 % higher under Flu20 treatment. Compared with CK treatment, SOD and POD activities promoted with increasing Flu concentration, whereas CAT activities decreased. Variability separation analysis revealed that level of IAA primarily influenced Flu accumulation in WT or under Flu5 treatments, whereas antioxidant enzyme activity primarily affected Flu accumulation in YUC1 or under Flu20 treatments. Exploring the relationship between the IAA synthesis gene YUCCA and IAA levels, alongside Flu accumulation, could yield novel insights into the regulation of PAH accumulation in plants.

Genetically Encoded, Noise-Tolerant, Auxin Biosensors in Yeast.

Auxins are crucial signaling molecules that regulate the growth, metabolism, and behavior of various organisms, most notably plants but also bacteria, fungi, and animals. Many microbes synthesize and perceive auxins, primarily indole-3-acetic acid (IAA, referred to as auxin herein), the most prevalent natural auxin, which influences their ability to colonize plants and animals. Understanding auxin biosynthesis and signaling in fungi may allow us to better control interkingdom relationships and microbiomes from agricultural soils to the human gut. Despite this importance, a biological tool for measuring auxin with high spatial and temporal resolution has not been engineered in fungi. In this study, we present a suite of genetically encoded, ratiometric, protein-based auxin biosensors designed for the model yeast Saccharomyces cerevisiae. Inspired by auxin signaling in plants, the ratiometric nature of these biosensors enhances the precision of auxin concentration measurements by minimizing clonal and growth phase variation. We used these biosensors to measure auxin production across diverse growth conditions and phases in yeast cultures and calibrated their responses to physiologically relevant levels of auxin. Future work will aim to improve the fold change and reversibility of these biosensors. These genetically encoded auxin biosensors are valuable tools for investigating auxin biosynthesis and signaling in S. cerevisiae and potentially other yeast and fungi and will also advance quantitative functional studies of the plant auxin perception machinery, from which they are built.

Metabolomic Analyses Reveal That IAA from Serratia marcescens Lkbn100 Promotes Plant Defense during Infection of Fusarium graminearum in Sorghum.

Global sorghum production has been significantly reduced due to the occurrence of sorghum root rot caused by the fungus Fusarium graminearum. The utilization of biocontrol microorganisms has emerged as an effective strategy. However, the underlying mechanisms remain unclear. Therefore, the aim of this study was to investigate the effectiveness of biocontrol bacteria in inducing sorghum resistance against sorghum root rot and explore the potential induced resistance mechanisms through metabolomics analysis. The results revealed that the biocontrol bacteria Lnkb100, identified as Serratia marcescens (GenBank: PP152264), significantly enhanced the resistance of sorghum against sorghum root rot and promoted its growth, leading to increased seed weight. Targeted metabolomics analysis demonstrated that the highest concentration of the hormone IAA (indole-3-acetic acid) was detected in the metabolites of Lnkb100. Treatment with IAA enhanced the activity of disease-related enzymes such as SOD, CAT, POD and PPO in sorghum, thereby improving its resistance against sorghum root rot. Further untargeted metabolomic analysis revealed that IAA treatment resulted in higher concentrations of metabolites involved in the resistance against F. graminearum, such as geniposidic acid, 5-L-Glutamyl-taurine, formononetin 7-O-glucoside-6″-O-malonate, as well as higher concentrations of the defense-related molecules volicitin and JA. Additionally, "secondary bile acid biosynthesis" and "glycerophospholipid metabolism" pathways were found to play significant roles in the defense response of sorghum against fungal infection. These findings provide a reliable theoretical basis for utilizing biocontrol microorganisms to control sorghum root rot.

Hormones metabolism as affected by LED blue light in citrus fruit.

The LED Blue Light (LBL) (450 nm) effect on hormones levels and on jasmonates (JAs) metabolism in oranges was investigated. The quantum flux (2 days, 60 µmol m-2. s-1) was chosen for its efficacy in reducing postharvest rot caused by this crop's main postharvest phytopathogenic fungus (Penicillium digitatum). The analysis of abscisic (ABA), salicylic (SA) and indole-3-acetic (IAA) acids, and of JAs-related metabolites, revealed that LBL modifies all studied metabolites and had major effects on JAs levels, mainly on jasmonic acid (JA) and its precursor cis-(+)-12-oxo-phytodienoic acid (OPDA). This agrees with the up-regulation of the genes participating in their synthesis. Results highlight the relevance of CsLOX1 and CsLOX5, and the contribution of CsAOC3, in the LBL-induced OPDA biosynthesis, whereas CsOPR2, CsACX1 and CsACX3 would play a part in the synthesis of JA from OPDA. Data also suggest that the applied LBL quantum flux favors fruit JA perception by increasing the expression of the coronatine insensitive 1 (COI1) receptor; and signaling by down-regulating abundant CsJAZ negative regulators. Differences in OPDA and JA between the LBL-treated oranges and their control fruit left in the dark disappeared after shifting the LBL-treated oranges to darkness for 3 more days. However, the LBL and darkness combination slightly increased IAA and SA contents.

Effect of Different Selenium Species on Indole-3-Acetic Acid Activity of Selenium Nanoparticles Producing Strain Bacillus altitudinis LH18.

Acting as a growth regulator, Indole-3-acetic acid (IAA) is an important phytohormone that can be produced by several Bacillus species. However, few studies have been published on the comprehensive evaluation of the strains for practical applications and the effects of selenium species on their IAA-producing ability. The present study showed the selenite reduction strain Bacillus altitudinis LH18, which is capable of producing selenium nanoparticles (SeNPs) at a high yield in a cost-effective manner. Bio-SeNPs were systematically characterized by using DLS, zeta potential, SEM, and FTIR. The results showed that these bio-SeNPs were small in particle size, homogeneously dispersed, and highly stable. Significantly, the IAA-producing ability of strain was differently affected under different selenium species. The addition of SeNPs and sodium selenite resulted in IAA contents of 221.7 µg/mL and 91.01 µg/mL, respectively, which were 3.23 and 1.33 times higher than that of the control. This study is the first to examine the influence of various selenium species on the IAA-producing capacity of Bacillus spp., providing a theoretical foundation for the enhancement of the IAA-production potential of microorganisms.

ß-Indole-3-acetic acid attenuated collagen-induced arthritis through reducing the ubiquitination of Foxp3 via the AhR-TAZ-Tip60 pathway.

Massive evidence shows that intestinal tryptophan metabolites affected by intestinal flora can modulate the progression of rheumatoid arthritis (RA). However, the effects and mechanisms of intestinal tryptophan metabolites on RA are not yet detailed. Herein, we investigated the protective effects of intestinal tryptophan metabolites on RA and its detailed mechanisms. In this study, the collagen-induced arthritis (CIA) rat model was established. Based on metabolomics analysis, the contents of ß-indole-3-acetic acid (IAA), indolylpropionic acid, and indole-3-ß-acrylic acid in the sera of CIA rats were significantly less compared with those of the normal rats. Under the condition of Treg or Th17 cell differentiation, IAA significantly promoted the differentiation and activation of Treg cells instead of Th17 cells. Intestinal tryptophan metabolites are well-known endogenic ligands of aryl hydrocarbon receptor (AhR). Not surprisingly, IAA increased the level of Foxp3 through activating the AhR pathway. Interestingly, IAA had little impact on the level of Foxp3 mRNA, but reducing the ubiquitination and degradation of Foxp3. Mechanically, IAA reduced the expression of the transcriptional coactivator TAZ, which was almost completely reversed by either AhR antagonist CH223191 or siRNA. In vitro, IAA decreased the combination of TAZ and the histone acetyltransferase Tip60, while it increased the combination of Tip60 and Foxp3. In CIA rats, oral administration of IAA increased the number of Treg cells and relieved the inflammation. A combined use with CH223191 almost abolished the effect of IAA. Taken together, IAA attenuated CIA by promoting the differentiation of Treg cells through reducing the ubiquitination of Foxp3 via the AhR-TAZ-Tip60 pathway.

Comparative Analysis of Plant Growth-Promoting Rhizobacteria's Effects on Alfalfa Growth at the Seedling and Flowering Stages under Salt Stress.

Alfalfa (Medicago sativa L.), a forage legume known for its moderate salt-alkali tolerance, offers notable economic and ecological benefits and aids in soil amelioration when cultivated in saline-alkaline soils. Nonetheless, the limited stress resistance of alfalfa could curtail its productivity. This study investigated the salt tolerance and growth-promoting characteristics (in vitro) of four strains of plant growth-promoting rhizobacteria (PGPR) that were pre-selected, as well as their effects on alfalfa at different growth stages (a pot experiment). The results showed that the selected strains belonged to the genera Priestia (HL3), Bacillus (HL6 and HG12), and Paenibacillus (HG24). All four strains exhibited the ability to solubilize phosphate and produce indole-3-acetic acid (IAA) and 1-aminocyclopropane-1-carboxylate (ACC) deaminase. Among them, except for strain HG24, the other strains could tolerate 9% NaCl stress. Treatment with 100 mM NaCl consistently decreased the IAA production levels of the selected strains, but inconsistent changes (either enhanced or reduced) in terms of phosphate solubilization, ACC deaminase, and exopolysaccharides (EPS) production were observed among the strains. During the various growth stages of alfalfa, PGPR exhibited different growth-promoting effects: at the seedling stage, they enhanced salt tolerance through the induction of physiological changes; at the flowering stage, they promoted growth through nutrient acquisition. The current findings suggest that strains HL3, HL6, and HG12 are effective microbial inoculants for alleviating salt stress in alfalfa plants in arid and semi-arid regions. This study not only reveals the potential of indigenous salt-tolerant PGPR in enhancing the salt tolerance of alfalfa but also provides new insights into the mechanisms of action of PGPR.

Identification of Flo11-like Adhesin in Schizosaccharomyces pombe and the Mechanism of Small-Molecule Compounds Mediating Biofilm Formation in Yeasts.

Fungal infection is initiated by the adhesion of pathogens to biotic and abiotic surfaces, with various manifestations including biofilm formation and invasive growth, etc. A previous report, though devoid of functional data, speculated that the Schizosaccharomyces pombe glycoprotein SPBPJ4664.02 could be the homology of Saccharomyces cerevisiae Flo11. Here, our studies with S. pombe substantiated the previously proposed speculation by (1) the deletion of SPBPJ4664.02 attenuated biofilm formation and invasive growth in S. pombe; (2) the S. pombe's lack of SPBPJ4664.02 could be complemented by expressing S. cerevisiae flo11. Furthermore, indole-3-acetic acid (IAA) and dodecanol were examined in S. pombe for their respective effects on biofilm formation. IAA and dodecanol at high concentrations could inhibit biofilm formation, whereas opposing effects were observed with low concentrations of these molecules. Mechanism studies with the SPBPJ4664.02Δ and SPBPJ4664.02Δ/flo11OE versus the wild type have demonstrated that IAA or dodecanol might exert regulatory effects downstream of SPBPJ4664.02 in the signaling pathway for biofilm formation. Moreover, our research extrapolated to Candida albicans has pinpointed that IAA inhibited biofilm formation at high concentrations, consistent with the transcriptional downregulation of the biofilm-related genes. Dodecanol suppressed C. albicans biofilm formation at all the concentrations tested, in accord with the downregulation of biofilm-related transcripts.

Transient efflux inhibition improves plant regeneration by natural auxins.

Plant genome editing and propagation are important tools in crop breeding and production. Both rely heavily on the development of efficient in vitro plant regeneration systems. Two prominent regeneration systems that are widely employed in crop production are somatic embryogenesis (SE) and de novo shoot regeneration. In many of the protocols for SE or shoot regeneration, explants are treated with the synthetic auxin analog 2,4-dichlorophenoxyacetic acid (2,4-D), since natural auxins, such as indole-3-acetic acid (IAA) or 4-chloroindole-3-acetic acid (4-Cl-IAA), are less effective or even fail to induce regeneration. Based on previous reports that 2,4-D, compared to endogenous auxins, is not effectively exported from plant cells, we investigated whether efflux inhibition of endogenous auxins could convert these auxins into efficient inducers of SE in Arabidopsis immature zygotic embryos (IZEs). We show that natural auxins and synthetic analogs thereof become efficient inducers of SE when their efflux is transiently inhibited by co-application of the auxin transport inhibitor naphthylphthalamic acid (NPA). Moreover, IZEs of auxin efflux mutants pin2 or abcb1 abcb19 show enhanced SE efficiency when treated with IAA or efflux-inhibited IAA, confirming that auxin efflux reduces the efficiency of Arabidopsis SE. Importantly, in contrast to the 2,4-D system, where only 50-60% of the embryos converted to seedlings, all SEs induced by transport-inhibited natural auxins converted to seedlings. Efflux-inhibited IAA, like 2,4-D, also efficiently induced SE from carrot suspension cells, whereas IAA alone could not, and efflux-inhibited 4-Cl-IAA significantly improved de novo shoot regeneration in Brassica napus. Our data provides new insights into the action of 2,4-D as an efficient inducer of plant regeneration but also shows that replacing this synthetic auxin for efflux-inhibited natural auxin significantly improves different types of plant regeneration, leading to a more synchronized and homogenous development of the regenerated plants.

Azospirillum isscasi sp. nov., a bacterium isolated from rhizosphere soil of rice.

A Gram-negative and rod-shaped bacterium, designated C340-1T, was isolated and screened from paddy soil in Zhongshan County, Guangxi Province, PR China. This strain grew at 20-42 °C (optimum, 37 °C), pH 5.0-9.0 (optimum, pH 7.0) and 0-4 % (w/v) NaCl (optimum, 0-1 %) on Reasoner's 2A medium. The strain could fix atmospheric nitrogen and acetylene reduction activity was recorded up to 120.26 nmol ethylene h-1 (mg protein)-1. Q-10 was the only isoprenoid quinone component; phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, an unidentified aminolipid and an unidentified polar lipid were the major polar lipids. Summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) and summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) were the primary cellular fatty acids. The genome of strain C340-1T was 6.18 Mb, and the G+C content was 69.0 mol%. Phylogenetic tree analysis based on 16S rRNA gene and 92 core genes showed that strain C340-1T was closely related to and clustered with the type strains Azospirillum brasilense JCM 1224T, Azospirillum argentinense Az39T, Azospirillum baldaniorum Sp245T and Azospirillum formosense JCM 17639T. The average nucleotide identity (ANI), average amino acid identity (AAI) and digital DNA-DNA hybridization (dDDH) values between strain C340-1T and the closely related type strains mentioned above were significantly lower than the threshold values for species classification (95-96 %, 95-96 % and 70 %, respectively). Based on phylogenetic, genomic, phenotypic, physiological and biochemical data, we have reason to believe that C340-1T represents a new species of the genus Azospirillum, for which the name Azospirillum isscasi sp. nov. is proposed. The type strain is C340-1T(=CCTCC AB 2023105T=KCTC 8126T).

Screening for Multifarious Plant Growth Promoting and Biocontrol Attributes in Bacillus Strains Isolated from Indo Gangetic Soil for Enhancing Growth of Rice Crops.

Multifarious plant growth-promoting Bacillus strains recovered from rhizospheric soils of the Indo Gangetic plains (IGPs) were identified as Bacillus licheniformis MNNITSR2 and Bacillus velezensis MNNITSR18 based on their biochemical characteristics and 16S rDNA gene analysis. Both strains exhibited the ability to produce IAA, siderophores, ammonia, lytic enzymes, HCN production, and phosphate solubilization capability and strongly inhibited the growth of phytopathogens such as Rhizoctonia solani and Fusariun oxysporum in vitro. In addition, these strains are also able to grow at a high temperature of 50 °C and tolerate up to 10-15% NaCl and 25% PEG 6000. The results of the pot experiment showed that individual seed inoculation and the coinoculation of multifarious plant growth promoting (PGP) Bacillus strains (SR2 and SR18) in rice fields significantly enhanced plant height, root length volume, tiller numbers, dry weight, and yield compared to the untreated control. This indicates that these strains are potential candidates for use as PGP inoculants/biofertilizers to increase rice productivity under field conditions for IGPs in Uttar Pradesh, India.

Dynamic Changes of Endogenous Hormones in Different Seasons of Idesia polycarpa Maxim.

Idesia polycarpa Maxim is a native dioecious tree from East Asia cultivated for its fruits and as an ornamental plant throughout temperate regions. Given the economic potential, comparative studies on cultivated genotypes are of current interest. This study aims to discover the dynamic changes and potential functions of endogenous hormones in I. polycarpa, as well as the differences in endogenous hormone contents in different growth stages among different I. polycarpa provenances. We used High-Performance Liquid Chromatography (HPLC) to measure and compare the levels of abscisic acid (ABA), indole-3-acetic acid (IAA), gibberellin A3 (GA3), and trans-Zeatin-riboside (tZR) in the leaves, flowers, and fruits of I. polycarpa from various provenances between April and October. Our findings indicated that changes in the ABA and GA3 content of plants from Jiyuan and Tokyo were minimal from April to October. However, the levels of these two hormones in Chengdu plants vary greatly at different stages of development. The peak of IAA content in the three plant materials occurred primarily during the early fruit stage and the fruit expansion stage. The concentration of tZR in the three plant materials varies greatly. Furthermore, we discovered that the contents of endogenous hormones in I. polycarpa leaves, flowers, and fruits from Chengdu provenances were slightly higher than those from Tokyo and Jiyuan provenances. The content of IAA was higher in male flowers than in female flowers, and the content of ABA, GA3, and tZR was higher in female flowers than in male flowers. According to the findings, the contents of these four endogenous hormones in I. polycarpa are primarily determined by the genetic characteristics of the trees and are less affected by cultivation conditions. The gender of I. polycarpa had a great influence on these four endogenous hormones. The findings of this study will provide a theoretical foundation and practical guidance for artificially regulating the flowering and fruiting of I. polycarpa.

ABA-responsive AREB1/ABI3-1/ABI5 cascade regulates IAA oxidase gene SlDAO2 to inhibit hypocotyl elongation in tomato.

Hypocotyl elongation is dramatically influenced by environmental factors and phytohormones. Indole-3-acetic acid (IAA) plays a prominent role in hypocotyl elongation, whereas abscisic acid (ABA) is regarded as an inhibitor through repressing IAA synthesis and signalling. However, the regulatory role of ABA in local IAA deactivation remains largely uncharacterized. In this study, we confirmed the antagonistic interplay of ABA and IAA during the hypocotyl elongation of tomato (Solanum lycopersicum) seedlings. We identified an IAA oxidase enzyme DIOXYGENASE FOR AUXIN OXIDATION2 (SlDAO2), and its expression was induced by both external and internal ABA signals in tomato hypocotyls. Moreover, the overexpression of SlDAO2 led to a reduced sensitivity to IAA, and the knockout of SlDAO2 alleviated the inhibitory effect of ABA on hypocotyl elongation. Furthermore, an ABA-responsive regulatory SlAREB1/SlABI3-1/SlABI5 cascade was identified to act upstream of SlDAO2 and to precisely control its expression. SlAREB1 directly bound to the ABRE present in the SlDAO2 promoter to activate SlDAO2 expression, and SlABI3-1 enhanced while SlABI5 inhibited the activation ability of SlAREB1 by directly interacting with SlAREB1. Our findings revealed that ABA might induce local IAA oxidation and deactivation via SlDAO2 to modulate IAA homoeostasis and thereby repress hypocotyl elongation in tomato.

The AP2/ERF transcription factor SlERF.J2 functions in hypocotyl elongation and plant height in tomato.

KEY MESSAGE: Our findings indicated that the SlERF.J2-IAA23 module integrates hormonal signals to regulate hypocotyl elongation and plant height in tomato. Light and phytohormones can synergistically regulate photomorphogenesis-related hypocotyl elongation and plant height in tomato. AP2/ERF family genes have been extensively demonstrated to play a role in light signaling and various hormones. In this study, we identified a novel AP2/ERF family gene in tomato, SlERF.J2. Overexpression of SlERF.J2 inhibits hypocotyl elongation and plant height. However, the plant height in the slerf.j2ko knockout mutant was not significantly changed compared with the WT. we found that hypocotyl cell elongation and plant height were regulated by a network involving light, auxin and gibberellin signaling, which is mediated by regulatory relationship between SlERF.J2 and IAA23. SlERF.J2 protein could bind to IAA23 promoter and inhibit its expression. In addition, light-dark alternation can activate the transcription of SlERF.J2 and promote the function of SlERF.J2 in photomorphogenesis. Our findings indicated that the SlERF.J2-IAA23 module integrates hormonal signals to regulate hypocotyl elongation and plant height in tomato.

Identification and Characterization of Auxin/IAA Biosynthesis Pathway in the Rice Blast Fungus Magnaporthe oryzae.

The rice blast fungus Magnaporthe oryzae has been known to produce the phytohormone auxin/IAA from its hyphae and conidia, but the detailed biological function and biosynthesis pathway is largely unknown. By sequence homology, we identified a complete indole-3-pyruvic acid (IPA)-based IAA biosynthesis pathway in M. oryzae, consisting of the tryptophan aminotransferase (MoTam1) and the indole-3-pyruvate decarboxylase (MoIpd1). In comparison to the wild type, IAA production was significantly reduced in the motam1Δ mutant, and further reduced in the moipd1Δ mutant. Correspondingly, mycelial growth, conidiation, and pathogenicity were defective in the motam1Δ and the moipd1Δ mutants to various degrees. Targeted metabolomics analysis further confirmed the presence of a functional IPA pathway, catalyzed by MoIpd1, which contributes to IAA/auxin production in M. oryzae. Furthermore, the well-established IAA biosynthesis inhibitor, yucasin, suppressed mycelial growth, conidiation, and pathogenicity in M. oryzae. Overall, this study identified an IPA-dependent IAA synthesis pathway crucial for M. oryzae mycelial growth and pathogenic development.

Exogenous Indole-3-Acetic Acid Induced Ethanol Tolerance in Phylogenetically Diverse Saccharomycetales Yeasts.

Indole-3-acetic acid (IAA) is an exogenous growth regulatory signal that is produced by plants and various microorganisms. Microorganisms have been suggested to cross-communicate with each other through IAA-mediated signaling mechanisms. The IAA-induced tolerance response has been reported in several microorganisms, but has not yet been described in Saccharomycetales yeasts. In the present study, three common stressors (heat, osmotic pressure, and ethanol) were examined in relation to the influence of a pretreatment with IAA on stress tolerance in 12 different lineages of Saccharomyces cerevisiae. The pretreatment with IAA had a significant effect on the induction of ethanol tolerance by reducing the doubling time of S. cerevisiae growth without the pretreatment. However, the pretreatment did not significantly affect the induction of thermo- or osmotolerance. The IAA pretreatment decreased the lethal effects of ethanol on S. cerevisiae cells. Although yeasts produce ethanol to outcompete sympatric microorganisms, IAA is not a byproduct of this process. Nevertheless, the accumulation of IAA indicates an increasing number of microorganisms, and, thus, greater competition for resources. Since the "wine trait" is shared by both phylogenetically related and distinct lineages in Saccharomycetales, we conclude that IAA-induced ethanol tolerance is not specific to S. cerevisiae; it may be widely detected in both pre-whole genome duplication (WGD) and post-WGD yeasts belonging to several genera of Saccharomycetales.

Phytotoxic Activity of Alkaloids in the Desert Plant Sophora alopecuroides.

Sophora alopecuroides is known to produce relatively large amounts of alkaloids; however, their ecological consequences remain unclear. In this study, we evaluated the allelopathic potential of the main alkaloids, including aloperine, matrine, oxymatrine, oxysophocarpine, sophocarpine, sophoridine, as well as their mixture both in distilled H2O and in the soil matrix. Our results revealed that all the alkaloids possessed inhibitory activity on four receiver species, i.e., Amaranthus retroflexus, Medicago sativa, Lolium perenne and Setaria viridis. The strength of the phytotoxicity of the alkaloids was in the following order: sophocarpine > aloperine > mixture > sophoridine > matrine > oxysophocarpine > oxymatrine (in Petri dish assays), and matrine > mixture > sophocarpine > oxymatrine > oxysophocarpine > sophoridine > aloperine (in pot experiments). In addition, the mixture of the alkaloids was found to significantly increase the IAA content, MDA content and POD activity of M. sativa seedlings, whereas CTK content, ABA content, SOD activity and CAT activity of M. sativa seedlings decreased markedly. Our results suggest S. alopecuroides might produce allelopathic alkaloids to improve its competitiveness and thus facilitate the establishment of its dominance; the potential value of these alkaloids as environmentally friendly herbicides is also discussed.

HOMEOBOX PROTEIN 24 mediates the conversion of indole-3-butyric acid to indole-3-acetic acid to promote root hair elongation.

Indole-3-acetic acid (IAA) is a predominant form of active auxin in plants. In addition to de novo biosynthesis and release from its conjugate forms, IAA can be converted from its precursor indole-3-butyric acid (IBA). The IBA-derived IAA may help drive root hair elongation in Arabidopsis thaliana seedlings, but how the IBA-to-IAA conversion is regulated and affects IAA function requires further investigation. In this study, HOMEOBOX PROTEIN 24 (HB24), a transcription factor in the zinc finger-homeodomain family (ZF-HD family) of proteins, was identified. With loss of HB24 function, defective growth occurred in root hairs. INDOLE-3-BUTYRIC ACID RESPONSE 1 (IBR1), which encodes an enzyme involved in the IBA-to-IAA conversion, was identified as a direct target of HB24 for the control of root hair elongation. The exogenous IAA or auxin analogue 1-naphthalene acetic acid (NAA) both rescued the root hair growth phenotype of hb24 mutants, but IBA did not, suggesting a role for HB24 in the IBA-to-IAA conversion. Therefore, HB24 participates in root hair elongation by upregulating the expression of IBR1 and subsequently promoting the IBA-to-IAA conversion. Moreover, IAA also elevated the expression of HB24, suggesting a feedback loop is involved in IBA-to-IAA conversion-mediated root hair elongation.

Endophytes from African Rice (Oryza glaberrima L.) Efficiently Colonize Asian Rice (Oryza sativa L.) Stimulating the Activity of Its Antioxidant Enzymes and Increasing the Content of Nitrogen, Carbon, and Chlorophyll.

Bacterial endophytes support the adaptation of host plants to harsh environments. In this study, culturable bacterial endophytes were isolated from the African rice Oryza glaberrima L., which is well-adapted to grow with poor external inputs in the tropical region of Mali. Among these, six N-fixer strains were used to inoculate O. glaberrima RAM133 and the Asian rice O. sativa L. cv. Baldo, selected for growth in temperate climates. The colonization efficiency and the N-fixing activity were evaluated and compared for the two rice varieties. Oryza sativa-inoculated plants showed a fairly good colonization efficiency and nitrogenase activity. The inoculation of Oryza sativa with the strains Klebsiella pasteurii BDA134-6 and Phytobacter diazotrophicus BDA59-3 led to the highest nitrogenase activity. In addition, the inoculation of 'Baldo' plants with the strain P. diazotrophicus BDA59-3 led to a significant increase in nitrogen, carbon and chlorophyll content. Finally, 'Baldo' plants inoculated with Kl. pasteurii BDA134-6 showed the induction of antioxidant enzymes activity and the maintenance of nitrogen-fixation under salt stress as compared to the unstressed controls. As these endophytes efficiently colonize high-yielding crop varieties grown in cold temperate climates, they become good candidates to promote their growth under unfavorable conditions.

Double agent indole-3-acetic acid: mechanistic analysis of indole-3-acetaldehyde dehydrogenase AldA that synthesizes IAA, an auxin that aids bacterial virulence.

The large diversity of organisms inhabiting various environmental niches on our planet are engaged in a lively exchange of biomolecules, including nutrients, hormones, and vitamins. In a quest to survive, organisms that we define as pathogens employ innovative methods to extract valuable resources from their host leading to an infection. One such instance is where plant-associated bacterial pathogens synthesize and deploy hormones or their molecular mimics to manipulate the physiology of the host plant. This commentary describes one such specific example-the mechanism of the enzyme AldA, an aldehyde dehydrogenase (ALDH) from the bacterial plant pathogen Pseudomonas syringae which produces the plant auxin hormone indole-3-acetic acid (IAA) by oxidizing the substrate indole-3-acetaldehyde (IAAld) using the cofactor nicotinamide adenine dinucleotide (NAD+) (Bioscience Reports (2020) 40(12), https://doi.org/10.1042/BSR20202959). Using mutagenesis, enzyme kinetics, and structural analysis, Zhang et al. established that the progress of the reaction hinges on the formation of two distinct conformations of NAD(H) during the reaction course. Additionally, a key mutation in the AldA active site 'aromatic box' changes the enzyme's preference for an aromatic substrate to an aliphatic one. Our commentary concludes that such molecular level investigations help to establish the nature of the dynamics of NAD(H) in ALDH-catalyzed reactions, and further show that the key active site residues control substrate specificity. We also contemplate that insights from the present study can be used to engineer novel ALDH enzymes for environmental, health, and industrial applications.