Journal of Experimental Botany最新文献

VASCULAR-RELATED NAC-DOMAIN7 (VND7) is a transcription factor gene that plays a critical role in xylem differentiation. The ectopic expression of VND7 induces the formation of secondary cell walls with spiral patterns in multiple plant cell types. In the present study, we have identified four homologs of VND7 in Nicotiana benthamiana and assigned them the names NbVND7-1 to NbVND7-4. Particularly, NbVND7-1 and NbVND7-2 were highly expressed during N. benthamiana and Arabidopsis thaliana (Nb/At) interfamily grafting. Analysis of the promoter GUS reporter lines of NbVND7 genes elucidated the expression of NbVND7-1 and NbVND7-2 in xylem tissues of intact and grafted plants, and those of NbVND7-3 and NbVND7-4 in internal phloem tissues. Gene network analysis revealed the downstream genes of each NbVND7 homolog and highlighted the association of NbVND7-1 and NbVND7-2 with xylem formation. A 𝛽-estradiol-inducible system for NbVND7-2 demonstrated that NbVND7-2 promotes ectopic xylem vessel differentiation in N. benthamiana seedlings and in the stem tissues at graft junction. Induction of NbVND7-2 at graft junction enhanced ectopic xylem formation in the callus tissues proliferated at graft boundary, accelerated the initiation of water transport from stock to scion, and enhanced scion stem growth after grafting. This study revealed a role of NbVND7 genes in xylem formation that can enhance Nicotiana interfamily grafting.

The triploid block, primarily caused by endosperm developmental issues, is known as a significant barrier to interploidy hybridization among flowering plants and thereby, polyploid speciation. However, its strength varies across taxa, with some instances of leakiness, questioning its universal role as a barrier. We conducted a literature survey to explore the causes of the variation in the strength of triploid block across 11 angiosperm families. We particularly assessed the impact of interploidy cross direction, types of endosperm development, endosperm persistence at seed maturity, and divergence between cytotypes using a Bayesian meta-analysis. We found a significant influence of the type of endosperm in shaping variation in triploid block strength. Other factors tested had no impact on triploid seed viability, likely due to limited data and inconsistencies in estimation methods across the literature. In addition, triploid seed viability in experimental crosses was sometimes correlated to the occurrence of triploid hybrids in nature, sometimes not, suggesting a mixed role of the triploid block in shaping interspecies gene flow. Altogether, our study highlights the need for unified approaches in future studies on the triploid block to advance our understanding of its variation and evolutionary implications.

Photosynthetic organisms have a high diversity of proteins belonging to the thioredoxin (TRX) superfamily. It comprises more than 150 proteins distributed in different families and classes, including in particular thioredoxins, glutaredoxins, protein disulfide isomerases, thiol peroxidases or glutathione transferases, which share the thioredoxin structural fold. Many of them have one or two redox-active cysteines and a characteristic cis-proline at specific positions, but also additional domains or secondary structures at either end or inserted into the protein core. With the aim of further describing the TRX family in plants, we identified a set of 17 atypical TRX-like proteins from Arabidopsis thaliana, which have not been considered before despite having both a TRX fold and the CxxC/S signature typical of redox-active TRX. The in silico sequence and structure analyses revealed that they are distributed in eight distinct classes with unique active site signatures and structures, some with DsbA and peroxiredoxin-like folds. The distinct subcellular localizations (plastids, mitochondria, extracellular space) and gene expression profiles suggest that these proteins are involved in diverse cellular processes, further expanding the set of proteins involved in redox regulation and/or stress adaptation. These results further reveal the diversity in structure and function of atypical TRXs in plants.

While sterile phenotypes of Osjar1 and Osaoc (hebiba) mutants corroborate the essential role of jasmonates (JAs) in reproductive development of rice (Oryza sativa L.), it remains unclear how other JA-dependent defense functions operate in reproductive tissues. We show that various JAs, including bioactive JA-Ile, gradually accumulate in the rice spikelets, and peak at anthesis, but majority of JAs remain localized in the stamens. While other spikelet parts contained only a low basal level of JAs, whole flowers responded to mechanical damage by the elicitation of a strong JA burst. Similarly, whole flowers increased their already present basal levels of defense metabolites in response to wounding, namely phenolamides and momilactone diterpenes, but these contents were only partially dependent on JA. Our data suggest that while JAs acquired essential role(s) in rice fertility, floral defense was largely diverted to yet another signaling pathway(s) that complement the canonical JA and/or JA-Ile stress signaling in reproductive parts of rice.

The gaseous plant hormone ethylene is a key developmental and growth regulator, and a pivotal endogenous response signal to abiotic and biotic interactions, including stress. Much of what is known about ethylene biosynthesis, perception and signaling comes from decades of research primarily in Arabidopsis thaliana and other eudicot model systems. In contrast, detailed knowledge on the ethylene pathway and response to the hormone is markedly limited in maize (Zea mays L.), a global cereal crop that is a major source of calories for humans and livestock, as well as a key industrial biofeedstock. Recent reports of forward screens and targeted reverse genetics have provided important insight into conserved and unique differences of the ethylene pathway and downstream responses. Natural and edited allelic variation in the promoter regions and coding sequences of ethylene biosynthesis and signaling genes alters maize shoot and root architectures, and plays a crucial role in biomass and grain yields. This review discusses recent advances in ethylene research in maize with an emphasis on ethylene's role in regulating growth and development of the shoot and root systems, and ultimately how this crucial hormone impacts plant architecture and grain yield.

The receptor kinase FERONIA (FER) is a multifaceted regulator of plant growth, development, reproduction and stress responses. FER is functionally connected to many plant hormones in diverse biological processes. This review summarizes the current understanding of the interplay between FER and phytohormones, with a focus on abscisic acid, ethylene, jasmonic acid, auxin and brassinosteroid. The mutual regulation between FER and plant hormones happens at multiple levels including ligands, receptors and downstream signaling components. Plant hormones can regulate the expression of genes encoding FER and its ligands RAPID ALKALINIZATION FACTORs (RALFs) as well as the abundance and kinase activity of FER proteins. On the other hand, FER can regulate hormone biosynthesis, transport, hormone perception and downstream signaling components such as transcription factors. Evidence of the crosstalk between FER and phytohormones are also emerging in crop species. Despite the rapid progress made in this field, more mechanistic studies are still needed to gain a comprehensive understanding of the FER-phytohormone crosstalk. Future research prospects and potential approaches are also discussed in this review.

The final steps of ethylene biosynthesis involve the consecutive activity of two enzymes, 1-aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxidase (ACO). These enzymes are encoded by small gene families, which, in the case of legumes, have not been systematically characterized at the level of gene family membership or phylogenetic relationships. Moreover, the absence of consensus nomenclature complicates comparisons within the scientific literature, where authors are addressing the roles of these genes in planta. In this study, we provide a framework in which the ACS and ACO family members of several legume species, including the two model legumes Medicago truncatula and Lotus japonicus, were systematically annotated, named, and analyzed relative to genes from other dicot and monocot model species. A combination of phylogenetic and reciprocal BLAST analyses was used to identify evolutionary relationships among genes, including the identification of orthologous relationships that can inform hypotheses about function. Given the role of ethylene as a negative regulator of the legume-rhizobium symbiosis, we queried publicly available RNA-seq expression datasets to obtain an overview of the expression profiles of these genes in the interaction between M. truncatula and its nitrogen-fixing microsymbiont. The resulting evolutionary framework, as well as structural and expression analyses, are intended to facilitate ongoing functional studies in legumes.

Climate change is expected to increase the frequency of heat waves, drought periods and flooding events, thereby posing a serious risk to crop productivity and global food security. In order to develop strategies to improve plant growth under adverse environmental conditions, in-depth molecular knowledge on plant stress responses is required. In this context, particular attention should be paid to the involvement of reactive oxygen species (ROS), molecules known for causing oxidative damage, but also indispensable for intra- and intercellular signal transduction required for plant acclimation to a wide variety of stress conditions. As plants often encounter multiple stressors simultaneously and their responses to these conditions can generally not be predicted based on the effects of the individual stress factors, the first part of this review focuses on the involvement of ROS and cellular redox homeostasis in plant responses to combined and multifactorial stress conditions. The second part of this work provides an overview of the role of ROS in priming strategies aimed at improving plant tolerance to climate change-related stress conditions. Finally, approaches to advance our understanding of redox dynamics in plant responses to combined stress and priming are discussed.

Recent evidence pointed to functional stomata on the abaxial side of barley leaf sheaths. However, the extent to which variation in sheath stomata densities (SD SheathAb) drives canopy water use and whether it has a genetic basis remains unknown. To address this, we phenotyped, twice, a mapping population consisting of 156 barley genotypes (936 plants) for their abaxial and adaxial leaf sheath and blade SDs, whole-plant transpiration rate (TR) and canopy conductance (Gs). Across the four SD traits, SD SheathAb exhibited the highest repeatability (0.73) and was the only one that correlated significantly and positively with TR and Gs. None of the quantitative trait loci (QTL) controlling leaf blade SD co-localized with TR and Gs QTL. In contrast, a major QTL common to SD SheathAb, TR and Gs was found on Chr 2H (PVE up to 50%), and mapped to a region enriched in F-box protein genes that included Ppd-H1. Gas exchange measurements confirmed that increases in SD SheathAb cause higher sheath-based transpiration, photosynthesis and stomatal conductance, and that sheath transpiration positively tracked with TR. Our investigation provides first-time evidence that genetic manipulation of SD SheathAb could improve crop water-use efficiency, with no apparent trade-offs with leaf blade gas exchange.