Journal of Experimental Botany最新文献

Plant growth depends on growth regulators, nutrient availability, and amino acid levels, all of which influence cell wall formation and cell expansion. Cell wall integrity and structures are surveyed and modified by a complex array of cell wall integrity sensors, including leucine-rich repeat (LRR)-extensins (LRXs) that bind RALF (rapid alkalinization factor) peptides with high affinity and help to compact cell walls. Expressing the Arabidopsis root hair-specific LRX1 without the extensin domain, which anchors the protein to the cell wall (LRX1ΔE14), has a negative effect on root hair development. The mechanism of this negative effect was investigated by a suppressor screen, which led to the identification of a sune (suppressor of dominant-negative LRX1ΔE14) mutant collection. The sune82 mutant was identified as an allele of HISN2, which encodes an enzyme essential for histidine biosynthesis. This mutation leads to reduced accumulation of histidine and an increase in several amino acids, which appears to have an effect on the TOR (target of rapamycin) network, a major controller of eukaryotic cell growth. It also represents an excellent tool to study the effects of reduced histidine levels on plant development, as it is a rare example of a viable partial loss-of-function allele in an essential biosynthetic pathway.

Cause-and-effect arrows are drawn from genotype (G), environment (E), and agronomic management (M) to the plant phenotype in crop stands in a useful but incomplete framework that informs research questions, experimental design, statistical analysis, data interpretation, modelling, and breeding and agronomic applications. Here we focus on the overlooked bidirectionality of these arrows. The phenotype-to-genotype arrow includes increased mutation rates in stressed phenotypes, relative to basal rates. From a developmental viewpoint, the phenotype modulates gene expression, returning multiple cellular phenotypes with a common genome. The phenotype-to-environment arrow is captured in the process of niche construction, which spans from persistent and global to transient and local. Research on crop rotations recognizes the influence of the phenotype on the environment but is divorced from niche construction theory. The phenotype-to-management arrow involves, for example, a diseased crop that may trigger fungicide treatment. Making explicit the bidirectionality of the arrows in the G×E×M framework contributes to narrowing the gap between data-driven technologies and integrative theory, and is an invitation to think cautiously of the internal teleonomy of plants in contrast to the view of the phenotype as the passive end of the arrows in the current framework.

The extensive use of nitrogen fertilizers has detrimental environmental consequences, and it is essential for society to explore sustainable alternatives. One promising avenue is engineering root nodule symbiosis, a naturally occurring process in certain plant species within the nitrogen-fixing clade, into non-leguminous crops. Advancements in single-cell transcriptomics provide unprecedented opportunities to dissect the molecular mechanisms underlying root nodule symbiosis at the cellular level. This review summarizes key findings from single-cell studies in Medicago truncatula, Lotus japonicus, and Glycine max. We highlight how these studies address fundamental questions about the development of root nodule symbiosis, including the following findings: (i) single-cell transcriptomics has revealed a conserved transcriptional program in root hair and cortical cells during rhizobial infection, suggesting a common infection pathway across legume species; (ii) characterization of determinate and indeterminate nodules using single-cell technologies supports the compartmentalization of nitrogen fixation, assimilation, and transport into distinct cell populations; (iii) single-cell transcriptomics data have enabled the identification of novel root nodule symbiosis genes and provided new approaches for prioritizing candidate genes for functional characterization; and (iv) trajectory inference and RNA velocity analyses of single-cell transcriptomics data have allowed the reconstruction of cellular lineages and dynamic transcriptional states during root nodule symbiosis.

The increasing frequency and intensity of low-temperature events in temperate and cold rice production regions threatens rice yields under climate change. While process-based crop models can project climate impacts on rice yield, their accuracy under low-temperature conditions has not been well evaluated. Our 6 year chamber experiments revealed that low temperatures reduce spikelet fertility from panicle initiation to flowering, grain number per spike during panicle development, and grain weight during grain filling. We examined the algorithms of spikelet fertility response to temperature used in crop models. The results showed that simulation performance is poor for crop yields if the same function was used at different growth stages outside the booting stage. Indeed, we replaced the algorithm for the spikelet fertility parameter of the ORYZA model and developed the function of estimated grain number per spike and grain weight. After that, the algorithm with improved equations was applied to 10 rice growth models. New functions considered the harmful effects of low temperatures on rice yield at different stages. In addition, the threshold temperatures of cold tolerance were set for different rice varieties. The improved algorithm enhances the ability of the models to simulate rice yields under climate change, providing a more reliable tool for adapting rice production to future climatic challenges.

Plants commonly undergo leaf morphoanatomy and composition modifications to cope with drought stress, and these tend to reduce mesophyll conductance to CO2 diffusion (gm), a key limitation to photosynthesis. The cell wall appears to play a crucial role in this reduction, yet the specific effect of cell wall component on gm and the underlying regulatory mechanisms of cell wall thickness (Tcw) variation are not well understood. In this study, we subjected cotton plants to varying levels of water deficit to investigate the impact of leaf cell wall component and the arrangement patterns of microfibrils within cell walls on Tcw and leaf gas exchange. Drought stress resulted in a significant thickening of cell walls and a decrease in gm. Concurrently, drought stress increased the content of chelator-soluble pectin and cellulose while reducing hemicellulose content. The alignment of cellulose microfibrils became more parallel and their diameter increased under drought conditions, suggesting a decrease in cell wall effective porosity which coincides with the observed reduction in gm. This research demonstrates that reduced gm typically observed under drought stress is related not only to thickened cell walls, but also to ultra-anatomical and compositional variations. Specifically, increases in cellulose content, diameter, and a highly aligned arrangement of cellulose microfibrils collectively contributed to an increase in Tcw, which, together with increases in chelator-soluble pectin content, resulted in an increased cell wall resistance to CO2 diffusion.

Plant peroxisomes are organelles housing different key metabolic pathways in the cell such as photorespiration and fatty acid β-oxidation. The metabolism of phytohormones, polyamines and other key signalling molecules such as reactive oxygen and nitrogen species (ROS and RNS) are housed in these organelles. The presence of a complex antioxidant system that may regulate ROS/RNS level makes peroxisomes a key organelle governing its dependent signalling. The evolution of -omics technologies and the existence of mutants with specifically altered ROS metabolism in peroxisomes, have provided us with a large amount of data and genes that could be regulated in plant responses to stress. All these data point to the existence of a specific transcriptomic footprint associated with peroxisomes. Furthermore, advances in microscopy and the implementation of new molecules have allowed us to visualize organelles in vivo and obtain detailed information about the dynamics of these organelles involving changes in their velocity, peroxules formation and proliferation. In this review, we update the latest information about peroxisomal metabolism and signalling, mainly related to ROS/RNS under control and stress conditions and how the different stimuli affect the plasticity and dynamic of the organelles, which can contribute in turn to plant responses to these stimuli.

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.