Journal of Experimental Botany最新文献

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.

Symplastic pathways involving plasma membrane H+-ATPases and Na+/H+ antiporters maintain sodium (Na+) homeostasis in the symplastic pathways and protect plant functions under salt stress. In this study, we characterised the effects of earthworms and arbuscular mycorrhizal fungi (AMF) on Na+ absorption and transport in roots. Measurements of root Na+ content, plasma membrane H+-ATPase and Na+/H+ antiporter and antioxidant enzyme activities were performed together with transcriptome analysis. The addition of earthworms and AMF under saline conditions decreased the accumulation of Na+ in maize roots and significantly increased the root K:Na ratios, as well as increasing the levels of transcripts encoding plasma membrane H+-ATPases, Na+/H+ antiporters, antioxidant enzymes and proteins involved in nitrogen and phosphorus uptake under saline conditions. The transcript changes induced by earthworms and AMF indicate that abscisic acid mediates the effects on salt tolerance. Taken together, these findings suggest that earthworms and AMF improve the salt tolerance of maize seedlings through improved symplastic pathways.

Abiotic stresses, including drought, salinity, temperature fluctuations, and nutrient deficiencies, challenge plant growth and productivity, requiring adaptive mechanisms for survival. Histone modifications, especially histone methylation, participate in gene expression regulation in response to these stresses. Notably, bivalent H3K4me3-H3K27me3 modifications play a central role in fine-tuning stress-responsive genes, allowing plants adapt to environmental changes. Recent studies have highlighted the dynamic switching of these bivalent chromatin marks at specific loci during stress, facilitating plant acclimatization to adverse environments. This review focuses on the four major histone H3 methylation modifications-H3K4, H3K9, H3K27, and H3K36-examining the roles of the associated methyltransferases and demethylases in mediating histone methylation dynamics. We synthesize recent findings on how these modifications regulate plant responses to various abiotic stresses, such as drought, salinity, heat, light stress, heavy metal exposure, and nutrient stress. By exploring these molecular mechanisms, we aim to deepen the understanding of how histone methylation shapes plant stress responses at both transcriptional and epigenetic levels. Furthermore, we also discuss the functional interaction of histone methylation with histone acetylation. These insights are critical for advancing breeding strategies aimed at improving plant tolerance to environmental stressors, ensuring food security, and supporting sustainable agricultural practices amid climate change.

Water stress presents a critical challenge affecting plant growth and agricultural productivity, with drought alone causing substantial yield losses. Roots serve as the primary site for water uptake, enabling plants to detect water stress by sensing changes in soil moisture levels. This initial perception prompts roots to initiate a spectrum of adaptive responses at morphological, anatomical, and biochemical levels. In addition to coping with severe water stress conditions like drought, roots also respond to microscale variations in water availability within the rhizosphere as they navigate through soil, exhibiting responses such as hydrotropism, xerobranching, and hydropatterning. These adaptive responses are orchestrated by dynamic and sophisticated sensing and signalling mechanisms mediated by plant hormones at the cellular level. This review explores recent advances in our understanding of root responses to water stress, emphasizing the hormonal mechanisms underpinning these adaptations. Furthermore, it outlines future perspectives aimed at enhancing crop resilience to water stress through improved understanding and manipulation of root-water interactions.