Integrated transcriptomic and metabolomic data reveal the cold stress responses molecular mechanisms of two coconut varieties.

Among tropical fruit trees, coconut holds significant edible and economic importance. The natural growth of coconuts faces a challenge in the form of low temperatures, which is a crucial factor among adverse environmental stresses impacting their geographical distribution. Hence, it is essential to enhance our comprehension of the molecular mechanisms through which cold stress influences various coconut varieties. We employed analyses of leaf growth morphology and physiological traits to examine how coconuts respond to low temperatures over 2-hour, 8-hour, 2-day, and 7-day intervals. Additionally, we performed transcriptome and metabolome analyses to identify the molecular and physiological shifts in two coconut varieties displaying distinct sensitivities to the cold stress. As the length of cold stress extended, there was a prominent escalation within the soluble protein (SP), proline (Pro) concentrations, the activity of peroxidase (POD) and superoxide dismutase (SOD) in the leaves. Contrariwise, the activity of glutathione peroxidase (GSH) underwent a substantial reduction during this period. The widespread analysis of metabolome and transcriptome disclosed a nexus of genes and metabolites intricately cold stress were chiefly involved in pathways centered around amino acid, flavonoid, carbohydrate and lipid metabolism. We perceived several stress-responsive metabolites, such as flavonoids, carbohydrates, lipids, and amino acids, which unveiled considerably, lower in the genotype subtle to cold stress. Furthermore, we uncovered pivotal genes in the amino acid biosynthesis, antioxidant system and flavonoid biosynthesis pathway that presented down-regulation in coconut varieties sensitive to cold stress. This study broadly enriches our contemporary perception of the molecular machinery that contributes to altering levels of cold stress tolerance amid coconut genotypes. It also unlocks several unique prospects for exploration in the areas of breeding or engineering, aiming to identifying tolerant and/or sensitive coconut varieties encompassing multi-omics layers in response to cold stress conditions.

Plant cadmium resistance 10 enhances tolerance to toxic heavy metals in poplar.

Toxic heavy metals originating from human activities have caused irreversible harm to the environment. Toxic heavy metal ions absorbed by crop plants can seriously threaten human health. Therefore, decreasing heavy metal contents in crop plants is an urgent need. The plant cadmium resistance protein (PCR) is a heavy metal ion transporter. In this study, PePCR10 was cloned from Populus euphratica. Bioinformatics analyses revealed its transmembrane structure and gene sequence motifs. The transcript profile of PePCR10 was analyzed by RT-qPCR, and its transcript levels increased under toxic heavy metal (cadmium, lead, aluminum) treatments. Subcellular localization analyses in tobacco cells revealed that PePCR10 localizes at the plasma membrane. Compared with wild type (WT), PePCR10-overexpressing lines showed significantly higher values for plant height, root length, fresh weight, and dry weight under heavy metal stress. Electrolyte leakage, nitroblue tetrazolium staining, and chlorophyll fluorescence analyses indicated that Cd/Al tolerance in PePCR10-overexpressing lines was stronger than that in WT. The Cd/Al contents were lower in the PePCR10-overexpressing lines than in WT under Cd/Al stress. Our results show that PePCR10 can reduce the heavy metal content in poplar and enhance its Cd/Al tolerance. Hence, PePCR10 is a candidate genetic resource for effectively reducing heavy metal accumulation in crops.

New potential transporter CIPAS8 enhances cadmium hypersensitivity and cobalt tolerance.

KEY MESSAGE: CIPAS8 is a novel Cd-influx and Co-efflux transporters, and Ser86 and Cys128 might play a decisive role in Co-binding and translocation. Cadmium (Cd) is among the most toxic heavy metals and is a widespread environmental pollutant. Cobalt (Co) is a mineral nutrient that is essential for plant growth and development, but high concentrations may be toxic. Cadmium-induced protein AS8 (CIPAS8) is widely distributed among plant species and might be induced by heavy metals, but its function has not been studied previously. In this study, Populus euphratica PeCIPAS8 and Salix linearistipularis SlCIPAS8 were investigated. The transcription of both genes was significantly enhanced under Cd and Co stresses. PeCIPAS8 and SlCIPAS8 conferred sensitivity to Cd in transgenic yeast, allowing higher quantities of Cd to accumulate within the cells, whereas SlCIPAS8 also conferred tolerance to Co and reduced Co accumulation. The determinants of substrate selectivity of the SlCIPAS8 protein were examined by site mutagenesis, which indicated that the Ser at 86th (S86) substituted for Arg (R) [S86R] and Cys at 128th (C128) substituted for Ser [C128S] mutations limited the protein's capability for Co translocation. These results suggested that PeCIPAS8 and SlCIPAS8 may be involved in Cd uptake into the plant cell. SlCIPAS8 can reduce excess Co accumulation to maintain intracellular Co homeostasis, and the site mutations S86R and C128S were essential for Co transport. These findings provide insight into the function of CIPAS8 and highlight its potential for utilization in phytoremediation applications.

Cadmium/lead tolerance of six Dianthus species and detoxification mechanism in Dianthus spiculifolius.

Toxic heavy metal contaminants seriously affect plant growth and human health. Reducing the accumulation of toxic metals by phytoremediation is an effective way to solve this environmental problem. Dianthus spiculifolius Schur is an ornamental plant with strong cold and drought tolerance. Because of its fast growth, well-developed root system, and large accumulation of biomass, D. spiculifolius has potential applications as a heavy metal hyperaccumulator. Therefore, the aim of this study was evaluate the ability of D. spiculifolius and other Dianthus species to remediate heavy metals, with an ultimate goal to identify available genetic resources for toxic metal removal. The cadmium (Cd) and lead (Pb) tolerance and accumulation of six Dianthus species were analyzed comparatively in physiological and biochemical experiments. Compared with the other Dianthus species, D. spiculifolius showed higher tolerance to, and greater accumulation of, Cd and Pb. Second-generation transcriptome analysis indicated that glutathione transferase activity was increased and the glutathione metabolism pathway was enriched with genes encoding antioxidant enzymes (DsGST, DsGST3, DsGSTU10, DsGGCT2-1, and DsIDH-2) that were up-regulated under Cd/Pb treatment by RT-qPCR in D. spiculifolius. When expressed in yeast, DsGST, DsGST3, DsGSTU10 and DsIDH-2 enhanced Cd or Pb tolerance. These results indicate that D. spiculifolius has potential applications as a new ornamental hyperaccumulator plant, and that antioxidant enzymes might be involved in regulating Cd/Pb accumulation and detoxification. The findings of this study reveal some novel genetic resources that can be used to breed new plant varieties that tolerate and accumulate heavy metals.

Plant cadmium resistance 6 from Salix linearistipularis (SlPCR6) affects cadmium and copper uptake in roots of transgenic Populus.

Phytoextraction in phytoremediation is one of the environmentally friendly methods used for restoring soils contaminated by heavy metals (HMs). The screening and identification of HM-resistant plants and their regulatory genes associated with HM ion transport are the key research aims in this field. In this study, a plant cadmium (Cd) resistance (PCR) gene family member, SlPCR6, was identified in roots of Salix linearistipularis, which exhibits strong HM resistance. The results revealed that SlPCR6 expression was induced in S. linearistipularis roots in response to Cd stress. Furthermore, SlPCR6 was mainly localized on the plasma membrane. Compared with the wild type, SlPCR6 overexpression reduced the Cd and copper (Cu) contents in the transgenic poplar (84 K) and increased its Cd and Cu resistance. The roots of transgenic poplar seedlings had lower net Cd and Cu uptake rates than wild type roots. Further investigation revealed that the transcript levels of multiple HM ion transporters were not significantly different between the roots of the wild type and those of the transgenic poplar. These results suggest that SlPCR6 is directly involved in Cd and Cu transport in S. linearistipularis roots. Therefore, SlPCR6 can serve as a candidate gene to improve the phytoextraction of the HMs Cd and Cu through genetic engineering.

AaZFP3, a Novel CCCH-Type Zinc Finger Protein from Adonis amurensis, Promotes Early Flowering in Arabidopsis by Regulating the Expression of Flowering-Related Genes.

CCCH-type zinc finger proteins (ZFP) are a large family of proteins that play various important roles in plant growth and development; however, the functions of most proteins in this family are uncharacterized. In this study, a CCCH-type ZFP, AaZFP3, was identified in the floral organ of Adonis amurensis. Quantitative real-time PCR (qPCR) analysis revealed that AaZFP3 was widely expressed in the flowers of A.amurensis. Subcellular localization analysis showed that the AaZFP3 protein was mainly localized to the cytoplasm in tobacco and Arabidopsis. Furthermore, the overexpression of AaZFP3 promoted early flowering in Arabidopsis under both normal and relatively low-temperature conditions. RNA-sequencing and qPCR analyses revealed that the expression of multiple key flowering-time genes was altered in transgenic Arabidopsis overexpressing AaZFP3 compared to wild-type. Of these genes, FLOWERING LOCUS T (AtFT) expression was most significantly up-regulated, whereas FLOWERING LOCUS C (AtFLC) was significantly down-regulated. These results suggest that the overexpression of AaZFP3 promotes early flowering in Arabidopsis by affecting the expression of flowering-time genes. Overall, our study indicates that AaZFP3 may be involved in flowering regulation in A.amurensis and may represent an important genetic resource for improving flowering-time control in other ornamental plants or crops.

[Effect of Gegen Qinlian Decoction on methylation and expression of Scd1gene in adipose tissue of insulin resistant rats and correlations between methylation and physiological and biochemical parameters].

This study aimed to explore the effect of Gegen Qinlian Decoction(GQD) on the methylation and mRNA expression level of stearoyl CoA desaturase(SCD) gene in the adipose tissue of rats with insulin resistance(IR) induced by high-fat diet as well as the correlations between methylation and physiological and biochemical indicators. The animals were divided into seven groups, namely, blank control(C) group, IR model group, low-(1.65 g·kg~(-1)), medium-(4.95 g·kg~(-1)), and high(14.85 g·kg~(-1))-dose GQD(GQDL, GQDM, and GQDH) groups, rosiglitazone(RGN, 5 mg·kg~(-1)) group, and simvastatin(SVT, 10 mg·kg~(-1)) group. The rat epididymal adipose tissue was collected for detecting all the cytosine methylation levels in two fragments of Scd1 gene by bisulfite sequencing PCR(BSP). Scd1-1 was located in CG shores and Scd1-2 in CG islands, including the transcriptional start site(TSS). The Scd1 mRNA level was determined by quantitative real-time PCR(q-PCR). Spearman correlation coefficient was used to analyze the correlations between amplified fragment C methylation and physiological and biochemical indicators. The results showed that GQDM remarkably reversed the elevated CG7 methylation in the TSS upstream region of Scd1-2 triggered by high-fat diet. GQDL significantly reversed the lowered total CG methylation in the downstream region of Scd1-2 induced by the high-fat diet. GQD did not significantly improve the decreased Scd1 mRNA expression caused by high-fat diet. Changes in methylation of the total CG, CG5 and CT11 of Scd1-1 in CG shores exhibited significant negative correlations with the serum triglyceride(TG) but positive correlation with the Scd1 mRNA level. The methylation of several C sites in the TSS upstream region of Scd1-2 was positively correlated with physiological and biochemical parameters. The methylation of several CG sites in the TSS downstream region of Scd1-2 was negatively associated with physiological and biochemical parameters. Besides, the methylation of several CH sites in the downstream fragment was positively correlated with physiological and biochemical parameters. All these have demonstrated that GQD may exert the therapeutic effect by regulating the methylation of CG7 in the TSS upstream region and total CG site in the TSS downstream region of Scd1 gene. The methylation of total CG, CG5 and CT11 sites in CG shores of Scd1 gene may be important targets for regulating Scd1 mRNA level and affecting serum TG.

Physiological and Gene Expression Responses of Six Annual Ryegrass Cultivars to Cobalt, Lead, and Nickel Stresses.

Heavy metals negatively affect soil quality and crop growth. In this study, we compared the tolerance of six ryegrass cultivars to cobalt (Co2+), lead (Pb2+), and nickel (Ni2+) stresses by analyzing their physiological indexes and transcript levels of genes encoding metal transporters. Compared with the other cultivars, the cultivar Lm1 showed higher germination rates and better growth under Co2+, Pb2+, or Ni2+ treatments. After 48 h of Co2+ treatment, the total antioxidant capacity of all six ryegrass cultivars was significantly increased, especially that of Lm1. In contrast, under Pb2+ stress, total antioxidant capacity of five cultivars was significantly decreased, but that of Lm1 was unaffected at 24 h. Staining with Evans blue dye showed that the roots of Lm1 were less injured than were roots of the other five ryegrass cultivars by Co2+, Pb2+, and Ni2+. Lm1 translocated and accumulated lesser Co2+, Pb2+, and Ni2+ than other cultivars. In Lm1, genes encoding heavy metal transporters were differentially expressed between the shoots and roots in response to Co2+, Pb2+, and Ni2+. The aim of these researches could help find potential resource for phytoremediation of heavy metal contamination soil. The identified genes related to resistance will be useful targets for molecular breeding.

High-quality reference genome sequences of two coconut cultivars provide insights into evolution of monocot chromosomes and differentiation of fiber content and plant height.

BACKGROUND: Coconut is an important tropical oil and fruit crop whose evolutionary position renders it a fantastic species for the investigation of the evolution of monocot chromosomes and the subsequent differentiation of ancient plants. RESULTS: Here, we report the assembly and annotation of reference-grade genomes of Cn. tall and Cn. dwarf, whose genome sizes are 2.40 Gb and 2.39 Gb, respectively. The comparative analysis reveals that the two coconut subspecies diverge about 2-8 Mya while the conserved Arecaceae-specific whole-genome duplication (ω WGD) occurs approximately 47-53 Mya. It additionally allows us to reconstruct the ancestral karyotypes of the ten ancient monocot chromosomes and the evolutionary trajectories of the 16 modern coconut chromosomes. Fiber synthesis genes in Cn. tall, related to lignin and cellulose synthesis, are found at a higher copy number and expression level than dwarf coconuts. Integrated multi-omics analysis reveals that the difference in coconut plant height is the result of altered gibberellin metabolism, with both the GA20ox copy number and a single-nucleotide change in the promoter together leading to the difference in plant height between Cn. tall and Cn. dwarf. CONCLUSION: We provide high-quality coconut genomes and reveal the genetic basis of trait differences between two coconuts through multi-omics analysis. We also reveal that the selection of plant height has been targeted for the same gene for millions of years, not only in natural selection of ancient plant as illustrated in coconut, but also for artificial selection in cultivated crops such as rice and maize.

Molecular Characterization of a Tolerant Saline-Alkali Chlorella Phosphatidate Phosphatase That Confers NaCl and Sorbitol Tolerance.

The gene encoding a putative phosphatidate phosphatase (PAP) from tolerant saline-alkali (TSA) Chlorella, ChPAP, was identified from a yeast cDNA library constructed from TSA Chlorella after a NaCl treatment. ChPAP expressed in yeast enhanced its tolerance to NaCl and sorbitol. The ChPAP protein from a GFP-tagged construct localized to the plasma membrane and the lumen of vacuoles. The relative transcript levels of ChPAP in Chlorella cells were strongly induced by NaCl and sorbitol as assessed by northern blot analyses. Thus, ChPAP may play important roles in promoting Na-ion movement into the cell and maintaining the cytoplasmic ion balance. In addition, ChPAP may catalyze diacylglycerol pyrophosphate to phosphatidate in vacuoles.

Identification and Characterization of MIKCc-Type MADS-Box Genes in the Flower Organs of Adonis amurensis.

Adonis amurensis is a perennial herbaceous flower that blooms in early spring in northeast China, where the night temperature can drop to -15 °C. To understand flowering time regulation and floral organogenesis of A. amurensis, the MIKCc-type MADS (Mcm1/Agamous/ Deficiens/Srf)-box genes were identified and characterized from the transcriptomes of the flower organs. In this study, 43 non-redundant MADS-box genes (38 MIKCc, 3 MIKC*, and 2 Mα) were identified. Phylogenetic and conserved motif analysis divided the 38 MIKCc-type genes into three major classes: ABCDE model (including AP1/FUL, AP3/PI, AG, STK, and SEPs/AGL6), suppressor of overexpression of constans1 (SOC1), and short vegetative phase (SVP). qPCR analysis showed that the ABCDE model genes were highly expressed mainly in flowers and differentially expressed in the different tissues of flower organs, suggesting that they may be involved in the flower organ identity of A. amurensis. Subcellular localization revealed that 17 full-length MADSs were mainly localized in the nucleus: in Arabidopsis, the heterologous expression of three full-length SOC1-type genes caused early flowering and altered the expression of endogenous flowering time genes. Our analyses provide an overall insight into MIKCc genes in A. amurensis and their potential roles in floral organogenesis and flowering time regulation.

Arabidopsis cold-regulated plasma membrane protein Cor413pm1 is a regulator of ABA response.

Cold-regulated (COR) genes are considered downstream functional genes in the cold-response pathway. However, we identified a plasma membrane-type, AtCor413pm1, as a regulatory gene for the abscisic acid (ABA) response, and found that ABA induced it predominantly in Arabidopsis roots, vasculature, stipules, and guard cells. Differentially expressed genes combined with qPCR analysis revealed the expressions of three ABA-responsive genes (AtDTX50, AtABR1, and AtCIPK20) were significantly altered in the ABA-treated atcor413pm1 mutant, compared to the wild-type. Furthermore, the ABA-induced transient Ca2+ oscillation in the plasma membrane of atcor413pm1 roots was different from that observed in the wild-type. Our results revealed that AtCor413pm1 might play a role in the cross-talk between the ABA and stress response pathways.

[Preliminary study on effect of Gegen Qinlian Decoction on enzyme activity, gene expression and methylation level of FASN in adipose tissue of rats with insulin resistance].

To investigate the effect of Gegen Qinlian Decoction(GQD) on enzyme activity, gene expression and methylation level of fatty acid synthase(FASN) in adipose tissue from rats with insulin resistance induced by high-fat diet. The 60% fat-powered high-fat diet was continuously given to male SD rats to induce the insulin resistance model. Then, they were divided into five groups randomly and administrated by gavage every day for 16 weeks with following drugs respectively: 10 mL·kg~(-1)water for control group(C) and insulin resistance model control group(IR), 1.65 g·kg~(-1)GQD per day for low-dose group(GQDL), 4.95 g·kg~(-1)GQD per day for medium-dose group(GQDM), 14.85 g·kg~(-1)GQD per day for high-dose group(GQDH), and 5 mg·kg~(-1) rosiglitazone per day for rosiglitazone group(RGN). Epididymal adipose tissue was taken to determine enzyme activity of FASN by colorimetric method, mRNA expression level of Fasn by quantitative Real-time PCR(Q-PCR) and CpGs methylation level between +313 and +582 by bisulfite sequencing PCR(BSP). These results showed that Fasn expression was significantly lowered in IR model rats compared with the control rats(P<0.01). Enzymatic activity and CpGs methylation level of Fasn in IR group showed downward trends. Low and medium-dose GQD can increase enzyme activity of FASN(P<0.05). Moreover, low-dose GQD increased the total CpGs methylation level of Fasn fragment between +313 and +582 in insulin resistance rats(P<0.05). For GQDM group, the methylation frequency of CpGs at positions +506 and +508(P<0.01) as well as the methylation frequency of CpGs on the binding sites of transcription factorzinc finger protein 161(P<0.05) were significantly increased. The methylation frequency of CpG at +442 position was positively correlated with Fasn expression(P<0.01, r=0.735), and methylation frequencies of CpGs at +345 and +366 positions were positively associated to enzyme activity of FASN respectively(P<0.05, r=0.479; P<0.01, r=0.640). In conclusion, GQD can reverse enzyme activity of FASN and methylation level of Fasn in adipose tissue of insulin resistant rats, and CpG sites at positions +506 and +508 may be the targets of GQD. The methylation level of CpGs at + 345 and + 366 sites were possibly related to FASN activity, while methylation of CpG at + 442 site may be closely correlated with mRNA level of Fasn. In addition, GQD did not significantly change mRNA expression level of Fasn, but effectively reversed enzymatic activity, suggesting that GQD may regulate the post transcriptional expression of Fasn.

Genome-wide discovery and characterization of long noncoding RNAs in African oil palm (Elaeis guineensis Jacq.).

Long noncoding RNAs (lncRNAs) are an important class of genes and play important roles in a range of biological processes. However, few reports have described the identification of lncRNAs in oil palm. In this study, we applied strand specific RNA-seq with rRNA removal to identify 1,363 lncRNAs from the equally mixed tissues of oil palm spear leaf and six different developmental stages of mesocarp (8-24 weeks). Based on strand specific RNA-seq data and 18 released oil palm transcriptomes, we systematically characterized the expression patterns of lncRNA loci and their target genes. A total of 875 uniq target genes for natural antisense lncRNAs (NAT-lncRNA, 712), long intergenic noncoding RNAs (lincRNAs, 92), intronic-lncRNAs (33), and sense-lncRNAs (52) were predicted. A majority of lncRNA loci (77.8%-89.6%) had low expression in 18 transcriptomes, while only 89 lncRNA loci had medium to high expression in at least one transcriptome. Coexpression analysis between lncRNAs and their target genes indicated that 6% of lncRNAs had expression patterns positively correlated with those of target genes. Based on single nucleotide polymorphism (SNP) markers derived from our previous research, 6,882 SNPs were detected for lncRNAs and 28 SNPs belonging to 21 lncRNAs were associated with the variation of fatty acid contents. Moreover, seven lncRNAs showed expression patterns positively correlated expression pattern with those of genes in de novo fatty acid synthesis pathways. Our study identified a collection of lncRNAs for oil palm and provided clues for further research into lncRNAs that may regulate mesocarp development and lipid metabolism.

Comparison of cadmium uptake and transcriptional responses in roots reveal key transcripts from high and low-cadmium tolerance ryegrass cultivars.

Cadmium (Cd), which seriously affects plant growth and crop production, is harmful to humans. Previous studies revealed ryegrass (Lolium multiflorum Lam.) exhibits Cd tolerance, and may be useful as a potential hyperaccumulator because of its wide distribution. In this study, the physiological and transcriptional responses of two ryegrass cultivars [i.e., high (LmHC) and low (LmLC) Cd tolerance] to Cd stress were investigated and compared. The Cd tolerance of LmHC was greater than that of LmLC at various Cd concentrations. The uptake of Evans blue dye revealed that Cd-induced root cell mortality was higher in LmLC than in LmHC after a 12-h Cd treatment. Furthermore, the content and influx rate of Cd in LmLC roots were greater than in LmHC roots under Cd stress conditions. The RNA sequencing and quantitative real-time PCR data indicated that the Cd transport regulatory genes (ABCG37, ABCB4, NRAMP4, and HMA5) were differentially expressed between the LmLC and LmHC roots. This expression-level diversity may contribute to the differences in the Cd accumulation and translocation between LmLC and LmHC. These findings may help clarify the physiological and molecular mechanisms underlying ryegrass responses to Cd toxicity. Additionally, ryegrass may be able to hyperaccumulate toxic heavy metals during the phytoremediation of contaminated soil.

Alternative splicing of flowering time gene FT is associated with halving of time to flowering in coconut.

Coconut palm has two distinct types-"tall" and "dwarf"-which differ morphologically. Tall coconut varieties need 8-10 years to start flowering, while dwarf coconut varieties only require 3-5 years. We compared seedling and reproductive stage transcriptomes for both coconut types to determine potential molecular mechanisms underlying control of flowering time in coconut. Several key genes in the photoperiod pathway were differentially expressed between seedling and reproductive leaf samples in both tall and dwarf coconut. These genes included suppressor of overexpression of constans (SOC1), flowering locus T (FT), and Apetala 1 (AP1). Alternative splicing analysis of genes in the photoperiod pathway further revealed that the FT gene produces different transcripts in tall compared to dwarf coconut. The shorter alternative splice variant of FT [which included a 6 bp deletion, alternative 3' splicing sites (A3SS)] was found to be exclusively present in dwarf coconut varieties but absent in most tall coconut varieties. Our results provide a valuable information resource as well as suggesting a probable mechanism for differentiation of flowering time onset in coconut, providing a target for future breeding work in accelerating time to flowering in this crop species.

Heterologous Expression of Nitrate Assimilation Related-Protein DsNAR2.1/NRT3.1 Affects Uptake of Nitrate and Ammonium in Nitrogen-Starved Arabidopsis.

Nitrogen (N) is an essential macronutrient for plant growth. Plants absorb and utilize N mainly in the form of nitrate (NO3-) or ammonium (NH4+). In this study, the nitrate transporter DsNRT3.1 (also known as the nitrate assimilation-related protein DsNAR2.1) was characterized from Dianthus spiculifolius. A quantitative PCR (qPCR) analysis showed that the DsNRT3.1 expression was induced by NO3-. Under N-starvation conditions, the transformed Arabidopsis seedlings expressing DsNRT3.1 had longer roots and a greater fresh weight than the wild type. Subcellular localization showed that DsNRT3.1 was mainly localized to the plasma membrane in Arabidopsis root hair cells. Non-invasive micro-test (NMT) monitoring showed that the root hairs of N-starved transformed Arabidopsis seedlings had a stronger NO3- and NH4+ influx than the wild-type seedlings, using with NO3- or NH4+ as the sole N source; contrastingly, transformed seedlings only had a stronger NO3- influx when NO3- and NH4+ were present simultaneously. In addition, the qPCR analysis showed that the expression of AtNRT2 genes (AtNRT2.1-2.6), and particularly of AtNRT2.5, in the transformed Arabidopsis differed from that in the wild type. Overall, our results suggest that the heterologous expression of DsNRT3.1 affects seedlings' growth by enhancing the NO3- and NH4+ uptake in N-starved Arabidopsis. This may be related to the differential expression of AtNRT2 genes.

The N-terminal and third transmembrane domain of PsCor413im1 are essential for targeting to chloroplast envelope membrane.

Cold-regulated (COR) genes, located downstream of the C-repeat binding factors (CBFs) in cold signaling pathways, play a central role in plant response to cold stress. In our previous studies, a Cor413 chloroplast envelope membrane protein, PsCor413im1, was identified from the cold-tolerant plant Phlox subulata. Its overexpression enhanced cold tolerance and altered AtCor15 expression in Arabidopsis. In the present study, the function of PsCor413im1 was further investigated. Transmission electron microscope observation showed that the chloroplast envelope membrane of cold-treated transgenic Arabidopsis seedlings was more stable than that of cold-treated wild-type seedlings. Subcellular localization of green fluorescent protein as a marker revealed that the N-terminal and putative third transmembrane domain (TMD) of PsCor413im1 were essential for its targeting of the chloroplast envelope membrane. Furthermore, overexpression of PsCor413im1 fragments containing N-terminal and third TMD also altered the expression of AtCor15 genes in Arabidopsis. Overall, our results suggest that PsCor413im1 may stabilize the chloroplast envelope membrane under cold stress, and its N-terminal and third TMD are important for its targeting capability and function.

Identifying Vitamin E Biosynthesis Genes in Elaeis guineensis by Genome-Wide Association Study.

Elaeis guineensis is a tropical oil crop and has the highest oil yield per unit area. Palm oil has high palmitic acid content and is also rich in vitamins, including vitamin E. We conducted genome-wide association studies in a diversity panel of 161 E. guineensis accessions to identify single-nucleotide polymorphisms (SNPs) linked with vitamin E and validated candidate genes in these marker-associated intervals. Based on the SNPs reported in our previous research, 47 SNP markers were detected to be significantly associated with the variation of tocopherol and tocotrienol content at a cutoff P value of 6.3 × 10-7. A total of 656 candidate genes in the flanking regions of the 47 SNPs were identified, followed by pathway enrichment analysis. Of these candidate genes, EgHGGT (homogentisate geranylgeranyl transferase) involved in the biosynthesis of tocotrienols had a higher expression level in the mesocarp compared to other tissues. Expression of the EgHGGT gene was positively correlated with the variation in α-tocotrienol content. Induced overexpression of the gene in Arabidopsis caused a significant increase in vitamin E content and production of α-tocotrienols compared to wild Arabidopsis.

Identification of Transcription Factors Involved in the Regulation of Flowering in Adonis Amurensis Through Combined RNA-seq Transcriptomics and iTRAQ Proteomics.

Temperature is one of the most important environmental factors affecting flowering in plants. Adonis amurensis, a perennial herbaceous flower that blooms in early spring in northeast China where the temperature can drop to -15 °C, is an ideal model for studying the molecular mechanisms of flowering at extremely low temperatures. This study first investigated global gene expression profiles at different developmental stages of flowering in A. amurensis by RNA-seq transcriptome and iTRAQ proteomics. Finally, 123 transcription factors (TFs) were detected in both the transcriptome and the proteome. Of these, 66 TFs belonging to 14 families may play a key role in multiple signaling pathways of flowering in A. amurensis. The TFs FAR1, PHD, and B3 may be involved in responses to light and temperature, while SCL, SWI/SNF, ARF, and ERF may be involved in the regulation of hormone balance. SPL may regulate the age pathway. Some members of the TCP, ZFP, MYB, WRKY, and bHLH families may be involved in the transcriptional regulation of flowering genes. The MADS-box TFs are the key regulators of flowering in A. amurensis. Our results provide a direction for understanding the molecular mechanisms of flowering in A. amurensis at low temperatures.