Monocotyledonous plants graft at the embryonic root-shoot interface.

Grafting is possible in both animals and plants. Although in animals the process requires surgery and is often associated with rejection of non-self, in plants grafting is widespread, and has been used since antiquity for crop improvement1. However, in the monocotyledons, which represent the second largest group of terrestrial plants and include many staple crops, the absence of vascular cambium is thought to preclude grafting2. Here we show that the embryonic hypocotyl allows intra- and inter-specific grafting in all three monocotyledon groups: the commelinids, lilioids and alismatids. We show functional graft unions through histology, application of exogenous fluorescent dyes, complementation assays for movement of endogenous hormones, and growth of plants to maturity. Expression profiling identifies genes that unify the molecular response associated with grafting in monocotyledons and dicotyledons, but also gene families that have not previously been associated with tissue union. Fusion of susceptible wheat scions to oat rootstocks confers resistance to the soil-borne pathogen Gaeumannomyces graminis. Collectively, these data overturn the consensus that monocotyledons cannot form graft unions, and identify the hypocotyl (mesocotyl in grasses) as a meristematic tissue that allows this process. We conclude that graft compatibility is a shared ability among seed-bearing plants.

Ceramides mediate positional signals in Arabidopsis thaliana protoderm differentiation.

The differentiation of distinct cell types in appropriate patterns is a fundamental process in the development of multicellular organisms. In Arabidopsis thaliana, protoderm/epidermis differentiates as a single cell layer at the outermost position. However, little is known about the molecular nature of the positional signals that achieve correct epidermal cell differentiation. Here, we propose that very-long-chain fatty acid-containing ceramides (VLCFA-Cers) mediate positional signals by stimulating the function of ARABIDOPSIS THALIANA MERISTEM LAYER1 (ATML1), a master regulator of protoderm/epidermis differentiation, during lateral root development. We show that VLCFA-Cers, which are synthesized predominantly in the outermost cells, bind to the lipid-binding domain of ATML1. Importantly, this cell type-specific protein-lipid association alters the activity of ATML1 protein and consequently restricts its expression to the protoderm/epidermis through a transcriptional feedback loop. Furthermore, establishment of a compartment, enriched with VLCFA-containing sphingolipids, at the outer lateral membrane facing the external environment may function as a determinant of protodermal cell fate. Taken together, our results indicate that VLCFA-Cers play a pivotal role in directing protoderm/epidermis differentiation by mediating positional signals to ATML1.This article has an associated 'The people behind the papers' interview.

Conserved LBL1-ta-siRNA and miR165/166-RLD1/2 modules regulate root development in maize.

Root system architecture and anatomy of monocotyledonous maize is significantly different from dicotyledonous model Arabidopsis The molecular role of non-coding RNA (ncRNA) is poorly understood in maize root development. Here, we address the role of LEAFBLADELESS1 (LBL1), a component of maize trans-acting short-interfering RNA (ta-siRNA), in maize root development. We report that root growth, anatomical patterning, and the number of lateral roots (LRs), monocot-specific crown roots (CRs) and seminal roots (SRs) are significantly affected in lbl1-rgd1 mutant, which is defective in production of ta-siRNA, including tasiR-ARF that targets AUXIN RESPONSE FACTOR3 (ARF3) in maize. Altered accumulation and distribution of auxin, due to differential expression of auxin biosynthesis and transporter genes, created an imbalance in auxin signalling. Altered expression of microRNA165/166 (miR165/166) and its targets, ROLLED1 and ROLLED2 (RLD1/2), contributed to the changes in lbl1-rgd1 root growth and vascular patterning, as was evident by the altered root phenotype of Rld1-O semi-dominant mutant. Thus, LBL1/ta-siRNA module regulates root development, possibly by affecting auxin distribution and signalling, in crosstalk with miR165/166-RLD1/2 module. We further show that ZmLBL1 and its Arabidopsis homologue AtSGS3 proteins are functionally conserved.

Supernumerary B chromosomes of Aegilops speltoides undergo precise elimination in roots early in embryo development.

Not necessarily all cells of an organism contain the same genome. Some eukaryotes exhibit dramatic differences between cells of different organs, resulting from programmed elimination of chromosomes or their fragments. Here, we present a detailed analysis of programmed B chromosome elimination in plants. Using goatgrass Aegilops speltoides as a model, we demonstrate that the elimination of B chromosomes is a strictly controlled and highly efficient root-specific process. At the onset of embryo differentiation B chromosomes undergo elimination in proto-root cells. Independent of centromere activity, B chromosomes demonstrate nondisjunction of chromatids and lagging in anaphase, leading to micronucleation. Chromatin structure and DNA replication differ between micronuclei and primary nuclei and degradation of micronucleated DNA is the final step of B chromosome elimination. This process might allow root tissues to survive the detrimental expression, or overexpression of B chromosome-located root-specific genes with paralogs located on standard chromosomes.

From Stained Plant Tissues to Quantitative Cell Segmentation Analysis with MorphoGraphX.

Development and growth of plant organs is determined by a myriad of molecular processes that occur in each individual cell. As a direct consequence of these processes, cells alter in size and shape. They therefore serve as excellent parameters to thoroughly understand gene function. However, conventional single-plane analyses fail to accurately capture cell metrics. Here, we present a comprehensive illustrated guide that demonstrates how SCRI Renaissance 2200 staining of Arabidopsis thaliana embryos and roots can be combined with the open-source application MorphoGraphX to quantify cell parameters in 3D. We compare this staining method with other common staining techniques and provide examples of embryo and root tissue segmentation. With our novel approach, subtle single-cell phenotypes can be identified in their native context, providing new possibilities to dissect gene networks.

POLTERGEIST and POLTERGEIST-LIKE1 are essential for the maintenance of post-embryonic shoot and root apical meristems as revealed by a partial loss-of-function mutant allele of pll1 in Arabidopsis.

BACKGROUND: POLTERGEIST (POL) and POL-LIKE1 (PLL1) encoding related protein phosphatase 2Cs are essential for the establishment of both shoot and root meristems during embryogenesis. As the strong pol pll1 are seedling-lethal due to the lack of hypocotyl vasculature, the roles of POL/PLL1 for the post-embryonic development is difficult to be assessed. OBJECTIVE: To prepare a weak pol pll1 double mutant that are able to produce post-embryonic organs. METHODS: Several T-DNA insertion mutants of pll1 were crossed to pol-6 for the preparation of weak pol pll1. To understand the epistatic interactions between POL/PLL1 and CLAVATAs, the phenotypes of clvs pol pll1 were assessed and the expression patterns of stem cell markers were examined in pol pll1. POLpro:PLL1-GFP expression was examined during the embryogenesis with confocal microscopy. RESULTS: We isolated a pll1-3 (S544N) allele and prepared a weak pol-6 pll1-3. About 5% of pol-6 pll1-3 seedlings continued the post-embryonic development displaying short roots with reduced root meristem, wuschel-like adventitious phyllotaxis, and defective flowers lacking carpel. The clv1, clv2, and clv3 phenotypes led by enlarged shoot meristems were almost completely suppressed in the pol-6 pll1-3. POL/PLL1 were required for the indeterminate floral organ development displayed by agamous. PLL1-GFP asymmetrically localized in the shootward sides of columella cells and increased the size of distal root meristem region by enhancing the WUS-RELATED HOMEOBOX 5 expression suggesting that PLL1 might provide the stem cells and progenies with proper positional information for the asymmetric cell divisions. CONCLUSION: Together, POL/PLL1 are required for the maintenance of stem cell pools for the post-embryonic development in Arabidopsis.

Optimization of Mature Embryo-Based Tissue Culture and Agrobacterium-Mediated Transformation in Model Grass Brachypodium distachyon.

Agrobacterium-mediated genetic transformation is well established in the model grass Brachypodium distachyon. However, most protocols employ immature embryos because of their better regenerative capacity. A major problem associated with the immature embryo system is that they are available only during a limited time window of growing plants. In this study, we have developed an optimized Agrobacterium-mediated genetic transformation protocol that utilizes mature embryos. We have adopted seed shearing and photoautotrophic rooting (PR) in callus induction and root regeneration, respectively, with evident significant improvement in these aspects. We have also revealed that the newly developed chemical inducer Fipexide (FPX) had the ability to induce callus, shoots, and roots. By comparison, we have demonstrated that FPX shows higher efficiency in shoot generation than other frequently used chemicals in our mature embryo-based system. In addition, we demonstrated that the age of embryogenetic callus severely affects the transformation efficiency (TE), with the seven-week-old embryogenetic callus having the highest TE reaching 52.6%, which is comparable with that in immature embryo transformation. The new methodologies reported here will advance the development and utilization of Brachypodium as a new model system for grass genomics.

The SMO1 Family of Sterol 4α-Methyl Oxidases Is Essential for Auxin- and Cytokinin-Regulated Embryogenesis.

In the plant sterol biosynthetic pathway, sterol 4α-methyl oxidase1 (SMO1) and SMO2 enzymes are involved in the removal of the first and second methyl groups at the C-4 position, respectively. SMO2s have been found to be essential for embryonic and postembryonic development, but the roles of SMO1s remain unclear. Here, we found that the three Arabidopsis (Arabidopsis thaliana) SMO1 genes displayed different expression patterns. Single smo1 mutants and smo1-1 smo1-3 double mutants showed no obvious phenotype, but the smo1-1 smo1-2 double mutant was embryo lethal. The smo1-1 smo1-2 embryos exhibited severe defects, including no cotyledon or shoot apical meristem formation, abnormal division of suspensor cells, and twin embryos. These defects were associated with enhanced and ectopic expression of auxin biosynthesis and response reporters. Consistently, the expression pattern and polar localization of PIN FORMED1, PIN FORMED7, and AUXIN RESISTANT1 auxin transporters were dramatically altered in smo1-1 smo1-2 embryos. Moreover, cytokinin biosynthesis and response were reduced in smo1-1 smo1-2 embryos. Tissue culture experiments further demonstrated that homeostasis between auxin and cytokinin was altered in smo1-1 smo1-2 heterozygous mutants. This disturbed balance of auxin and cytokinin in smo1-1 smo1-2 embryos was accompanied by unrestricted expression of the quiescent center marker WUSCHEL-RELATED HOMEOBOX5 Accordingly, exogenous application of either auxin biosynthesis inhibitor or cytokinin partially rescued the embryo lethality of smo1-1 smo1-2 Sterol analyses revealed that 4,4-dimethylsterols dramatically accumulated in smo1-1 smo1-2 heterozygous mutants. Together, these data demonstrate that SMO1s function through maintaining correct sterol composition to balance auxin and cytokinin activities during embryogenesis.

Redundant SCARECROW genes pattern distinct cell layers in roots and leaves of maize.

The highly efficient C4 photosynthetic pathway is facilitated by 'Kranz' leaf anatomy. In Kranz leaves, closely spaced veins are encircled by concentric layers of photosynthetic bundle sheath (inner) and mesophyll (outer) cells. Here, we demonstrate that, in the C4 monocot maize, Kranz patterning is regulated by redundant function of SCARECROW 1 (ZmSCR1) and a previously uncharacterized homeologue: ZmSCR1h. ZmSCR1 and ZmSCR1h transcripts accumulate in ground meristem cells of developing leaf primordia and in Zmscr1;Zmscr1h mutant leaves, most veins are separated by one rather than two mesophyll cells; many veins have sclerenchyma above and/or below instead of mesophyll cells; and supernumerary bundle sheath cells develop. The mutant defects are unified by compromised mesophyll cell development. In addition to Kranz defects, Zmscr1;Zmscr1h mutants fail to form an organized endodermal layer in the root. Collectively, these data indicate that ZmSCR1 and ZmSCR1h redundantly regulate cell-type patterning in both the leaves and roots of maize. Leaf and root pathways are distinguished, however, by the cell layer in which they operate - mesophyll at a two-cell distance from leaf veins versus endodermis immediately adjacent to root vasculature.

Spatiotemporal Developmental Trajectories in the Arabidopsis Root Revealed Using High-Throughput Single-Cell RNA Sequencing.

High-throughput single-cell RNA sequencing (scRNA-seq) is becoming a cornerstone of developmental research, providing unprecedented power in understanding dynamic processes. Here, we present a high-resolution scRNA-seq expression atlas of the Arabidopsis root composed of thousands of independently profiled cells. This atlas provides detailed spatiotemporal information, identifying defining expression features for all major cell types, including the scarce cells of the quiescent center. These reveal key developmental regulators and downstream genes that translate cell fate into distinctive cell shapes and functions. Developmental trajectories derived from pseudotime analysis depict a finely resolved cascade of cell progressions from the niche through differentiation that are supported by mirroring expression waves of highly interconnected transcription factors. This study demonstrates the power of applying scRNA-seq to plants and provides an unparalleled spatiotemporal perspective of root cell differentiation.

Stable isotope natural abundances (δ13C and δ15N) and carbon-water relations as drought stress mechanism response of taro (Colocasia esculenta L. Schott).

Taro (Colocasia esculenta L. Schott) is an important staple food crop in tropical and developing countries, having high water requirements. The purpose of this study was to evaluate the feasibility of using carbon and nitrogen isotopic composition (δ13C and δ15N) as a physiological indicator of taro response to drought, and elucidation of the relationship between the water use efficiency (WUE) under drought conditions and carbon isotope discrimination (Δ13C). As an alternative to WUE determination, obtained by measuring plant growth and water loss during an entire vegetative cycle, we have used Δ13C to determine the tolerance of C3 taro plants to drought. Seven taro accessions from Madeira, Canary Islands and the Secretariat of the Pacific Community (Fiji) collections were grown under greenhouse conditions and subjected to different watering regimes during a one-year cycle. Total plant biomass (TPB), WUE and δ15N were determined at the whole-plant level (WP). Corms and shoots were evaluated separately for nitrogen content (N), δ13C, Δ13C and δ15N. WUE showed positive correlation with TPB (r = 0.4) and negative with Δ13C (r = -0.3); Corm δ15N showed positive correlations with WP δ15N (r = 0.6) and corm N (r = 0.3). Accordingly, the taro plants with enhanced WUE exhibited low Δ13C and δ15N values as a physiological response to drought stress. The approach used in the present study has developed new tools that could be used in further research on taro response to environmental stresses.

Local Auxin Biosynthesis Is a Key Regulator of Plant Development.

Auxin is a major phytohormone that controls numerous aspects of plant development and coordinates plant responses to the environment. Morphogenic gradients of auxin govern cell fate decisions and underlie plant phenotypic plasticity. Polar auxin transport plays a central role in auxin maxima generation. The discovery of the exquisite spatiotemporal expression patterns of auxin biosynthesis genes of the WEI8/TAR and YUC families suggested that local auxin production may contribute to the formation of auxin maxima. Herein, we systematically addressed the role of local auxin biosynthesis in plant development and responses to the stress phytohormone ethylene by manipulating spatiotemporal patterns of WEI8. Our study revealed that local auxin biosynthesis and transport act synergistically and are individually dispensable for root meristem maintenance. In contrast, flower fertility and root responses to ethylene require local auxin production that cannot be fully compensated for by transport in the generation of morphogenic auxin maxima.

The Role of the Primary Cell Wall in Plant Morphogenesis.

Morphogenesis remains a riddle, wrapped in a mystery, inside an enigma. It remains a formidable problem viewed from many different perspectives of morphology, genetics, and computational modelling. We propose a biochemical reductionist approach that shows how both internal and external physical forces contribute to plant morphogenesis via mechanical stress⁻strain transduction from the primary cell wall tethered to the plasma membrane by a specific arabinogalactan protein (AGP). The resulting stress vector, with direction defined by Hechtian adhesion sites, has a magnitude of a few piconewtons amplified by a hypothetical Hechtian growth oscillator. This paradigm shift involves stress-activated plasma membrane Ca2+ channels and auxin-activated H⁺-ATPase. The proton pump dissociates periplasmic AGP-glycomodules that bind Ca2+. Thus, as the immediate source of cytosolic Ca2+, an AGP-Ca2+ capacitor directs the vectorial exocytosis of cell wall precursors and auxin efflux (PIN) proteins. In toto, these components comprise the Hechtian oscillator and also the gravisensor. Thus, interdependent auxin and Ca2+ morphogen gradients account for the predominance of AGPs. The size and location of a cell surface AGP-Ca2+ capacitor is essential to differentiation and explains AGP correlation with all stages of morphogenetic patterning from embryogenesis to root and shoot. Finally, the evolutionary origins of the Hechtian oscillator in the unicellular Chlorophycean algae reflect the ubiquitous role of chemiosmotic proton pumps that preceded DNA at the dawn of life.

An Ancestral Allele of Pyrroline-5-carboxylate synthase1 Promotes Proline Accumulation and Drought Adaptation in Cultivated Barley.

Water scarcity is a critical threat to global crop production. Here, we used the natural diversity of barley (Hordeum vulgare) to dissect the genetic control of proline (Pro) mediated drought stress adaptation. Genetic mapping and positional cloning of a major drought-inducible quantitative trait locus (QPro.S42-1H) revealed unique allelic variation in pyrroline-5-carboxylate synthase (P5cs1) between the cultivated cultivar Scarlett (ssp. vulgare) and the wild barley accession ISR42-8 (ssp. spontaneum). The putative causative mutations were located in the promoter of P5cs1 across the DNA binding motifs for abscisic acid-responsive element binding transcription factors. Introgression line (IL) S42IL-143 carrying the wild allele of P5cs1 showed significant up-regulation of P5cs1 expression compared to Scarlett, which was consistent with variation in Pro accumulation under drought. Next, we transiently expressed promoter::reporter constructs of ISR42-8 and Scarlett alleles in Arabidopsis (Arabidopsis thaliana) mesophyll protoplasts. GUS expression analysis showed a significantly higher activation of the ISR42-8 promoter compared to Scarlett upon abscisic acid treatment. Notably, the ISR42-8 promoter activity was impaired in protoplasts isolated from the loss-of-function abf1abf2abf3abf4 quadruple mutant. A series of phenotypic evaluations demonstrated that S42IL-143 maintained leaf water content and photosynthetic activity longer than Scarlett under drought. These findings suggest that the ancestral variant of P5cs1 has the potential for drought tolerance and understanding drought physiology of barley and related crops.

Root stem cell niche organizer specification by molecular convergence of PLETHORA and SCARECROW transcription factor modules.

Continuous formation of somatic tissues in plants requires functional stem cell niches where undifferentiated cells are maintained. In Arabidopsis thaliana, PLETHORA (PLT) and SCARECROW (SCR) genes are outputs of apical-basal and radial patterning systems, and both are required for root stem cell specification and maintenance. The WUSCHEL-RELATED HOMEOBOX 5 (WOX5) gene is specifically expressed in and required for functions of a small group of root stem cell organizer cells, also called the quiescent center (QC). PLT and SCR are required for QC function, and their expression overlaps in the QC; however, how they specify the organizer has remained unknown. We show that PLT and SCR genetically and physically interact with plant-specific teosinte-branched cycloidea PCNA (TCP) transcription factors to specify the stem cell niche during embryogenesis and maintain organizer cells post-embryonically. PLT-TCP-SCR complexes converge on PLT-binding sites in the WOX5 promoter to induce expression.

Mitogen-activated protein kinases concentrate in the vicinity of chromosomes and may regulate directly cellular patterning in Vicia faba embryos.

MAIN CONCLUSION: Mitogen-activated protein kinases seem to mark genes which are set up to be activated in daughter cells and thus they may play a direct role in cellular patterning during embryogenesis. Embryonic patterning starts very early and after the first division of zygote different genes are expressed in apical and basal cells. However, there is an ongoing debate about the way these different transcription patterns are established during embryogenesis. The presented data indicate that mitogen-activated protein kinases (MAPKs) concentrate in the vicinity of chromosomes and form visible foci there. Cells in the apical and basal regions differ in number of foci observed during the metaphase which suggests that cellular patterning may be determined by activation of diverse MAPK-dependent genes. Different number of foci in each group of separating chromatids and the specified direction of these mitoses in apical-basal axis indicate that the unilateral auxin accumulation in a single cell may regulate the number of foci in each group of chromatids. Thus, we put forward a hypothesis that MAPKs localized in the vicinity of chromosomes during mitosis mark those genes which are set up to be activated in daughter cells after division. It implies that the chromosomal localization of MAPKs may be one of the mechanisms involved in establishment of cellular patterns in some plant species.

Effect of AgNO3 and BAP on Root as a Novel Explant in Date Palm (Phoenix dactylifera cv. Medjool) Somatic Embryogenesis.

BACKGROUND AND OBJECTIVE: Somatic embryogenesis techniques are used for cloning a wide range of varieties of date palms around the world. The aim of the present study was to develop an efficient method with the lowest cost and the greatest potential to obtain in vitro plantlets of date palm cv. Medjool. Also, produce embryogenic callus and somatic embryos without using 2,4-dichlorophenoxyacetic acid (2,4-D). METHODOLOGY: In this study, produced plantlets through somatic embryogenesis were used in vitro roots as explant cultured on Murashige and Skoog (MS) media containing three level of Silver Nitrate (AgNO3) (0, 3 and 6 mg L-1) plus two level of 6-benzylaminopurine (BAP) (0 and 2 mg L-1) plus 0.1 mg L-1 1-naphthylacetic acid (NAA) for callus induction. After 12 weeks of culture, callus induction and after 16 weeks, production of embryogenic callus and embryos were occurred from root explants. RESULTS: According to the results, medium containing 2 mg L-1 BAP and 3 mg L-1 silver nitrate+0.1 mg L-1 NAA showed the highest amount of embryogenic callus fresh weight (1.38 g). This treatment also cause the highest number and length of embryos by production of 90.04 embryogenic callus with length of 11.18 mm. On the other hand, shoots were appeared from germinated embryos and white roots began to appear within 8 weeks. Medium contains 3 mg L-1 BAP and 0.1 mg L-1 NAA with average of 12.27 cm shoot length and 15.48 cm root length was the best. Control treatment had the lowest average shoot (3.71 cm) and root (5.03 cm) length. CONCLUSION: This study showed that certain concentration of silver nitrate and BAP has stimulating effect on growth of produced embryonic callus from root segments of Medjool cultivar of date palm.

Redox Changes During the Cell Cycle in the Embryonic Root Meristem of Arabidopsis thaliana.

AIMS: The aim of this study was to characterize redox changes in the nuclei and cytosol occurring during the mitotic cell cycle in the embryonic roots of germinating Arabidopsis seedlings, and to determine how redox cycling was modified in mutants with a decreased capacity for ascorbate synthesis. RESULTS: Using an in vivo reduction-oxidation (redox) reporter (roGFP2), we show that transient oxidation of the cytosol and the nuclei occurred at G1 in the synchronized dividing cells of the Arabidopsis root apical meristem, with reduction at G2 and mitosis. This redox cycle was absent from low ascorbate mutants in which nuclei were significantly more oxidized than controls. The cell cycle-dependent increase in nuclear size was impaired in the ascorbate-deficient mutants, which had fewer cells per unit area in the root proliferation zone. The transcript profile of the dry seeds and size of the imbibed seeds was strongly influenced by low ascorbate but germination, dormancy release and seed aging characteristics were unaffected. INNOVATION: These data demonstrate the presence of a redox cycle within the plant cell cycle and that the redox state of the nuclei is an important factor in cell cycle progression. CONCLUSIONS: Controlled oxidation is a key feature of the early stages of the plant cell cycle. However, sustained mild oxidation restricts nuclear functions and impairs progression through the cell cycle leading to fewer cells in the root apical meristem. Antioxid. Redox Signal. 27, 1505-1519.

Non-ribosomal Peptide Synthases from Pseudomonas aeruginosa Play a Role in Cyclodipeptide Biosynthesis, Quorum-Sensing Regulation, and Root Development in a Plant Host.

Diverse molecules mediate cross-kingdom communication between bacteria and their eukaryotic partners and determine pathogenic or symbiotic relationships. N-acyl-L-homoserine lactone-dependent quorum-sensing signaling represses the biosynthesis of bacterial cyclodipeptides (CDPs) that act as auxin signal mimics in the host plant Arabidopsis thaliana. In this work, we performed bioinformatics, biochemical, and plant growth analyses to identify non-ribosomal peptide synthase (NRPS) proteins of Pseudomonas aeruginosa, which are involved in CDP synthesis. A reverse genetics strategy allowed the identification of the genes encoding putative multi-modular-NRPS (MM-NRPS). Mutations in these genes affected the synthesis of the CDPs cyclo(L-Pro-L-Val), cyclo(L-Pro-L-Leu), and cyclo(L-Pro-L-Tyr), while showing wild-type-like levels of virulence factors, such as violacein, elastase, and pyocyanin. When analyzing the bioactivity of purified, naturally produced CDPs, it was found that cyclo(L-Pro-L-Tyr) and cyclo(L-Pro-L-Val) were capable of antagonizing quorum-sensing-LasR (QS-LasR)-dependent signaling in a contrasting manner in the cell-free supernatants of the selected NRPS mutants, which showed QS induction. Using a bacteria-plant interaction system, we further show that the pvdJ, ambB, and pchE P. aeruginosa mutants failed to repress primary root growth, but improved root branching in A. thaliana seedlings. These results indicated that the CDP production in P. aeruginosa depended on the functional MM-NRPS, which influences quorum-sensing of bacteria and plays a role in root architecture remodeling.

NtKRP, a kinesin-12 protein, regulates embryo/seed size and seed germination via involving in cell cycle progression at the G2/M transition.

Kinesins comprise a superfamily of microtubule-based motor proteins involved in essential processes in plant development, but few kinesins have been functionally identified during seed development. Especially, few kinesins that regulate cell division during embryogenesis have been identified. Here we report the functional characterization of NtKRP, a motor protein of the kinesin-12 family. NtKRP is predominantly expressed in embryos and embryonic roots. NtKRP RNAi lines displayed reductions in cell numbers in the meristematic zone, in embryonic root length, and in mature embryo and seed sizes. Furthermore, we also show that CDKA;1 binds to NtKRP at the consensus phosphorylation sites and that the decreased cell numbers in NtKRP-silenced embryos are due to a delay in cell division cycle at the G2/M transition. In addition, binding between the cargo-binding tail domain of NtKRP and CDKA; 1 was also determined. Our results reveal a novel molecular pathway that regulates embryo/seed development and critical role of kinesin in temporal and spatial regulation of a specific issue of embryo developmental.