Journal of Experimental Botany最新文献

Plant viral vectors are powerful tools for transient gene overexpression and silencing, enabling rapid functional analysis without the need for genetic transformation. Rice stripe mosaic virus (RSMV) is an emerging plant rhabdovirus transmitted propagatively by the leafhopper Recilia dorsalis. Leveraging its cross-kingdom replication ability, here we report the development of RSMV as a versatile vector for regulatable foreign gene expression and virus-induced gene silencing (VIGS) in rice and its insect vector. We first established an efficient reverse genetics system for RSMV using Nicotiana benthamiana as a model host. Recombinant virus particles recovered from N. benthamiana leaves were infectious to R. dorsalis and efficiently transmitted to rice. RSMV-based vectors stably accommodated at least two foreign genes, totaling up to 3.7 kb, and maintained stable expression across multiple passages. As proof-of-concept, the RSMV-VIGS vector achieved >90% knockdown of a target gene in R. dorsalis, producing near-knockout phenotypes that persisted throughout adulthood, and also induced efficient gene silencing in infected rice plants. Our work enables genetic manipulation of RSMV for molecular studies and provides a robust tool for functional genomics in both rice and insect hosts.

Forest trees face numerous biotic challenges throughout their life cycle, including pathogens and leaf-chewing insects. Our previous research suggested that certain members of the RING ZINC FINGER PROTEIN (RZFP) family, particularly PtrRZFP1 in Populus trichocarpa, may play a role in insect-plant interactions. In this study, we found that the PtrRZFP1 gene is significantly upregulated by exogenous methyl jasmonate (MeJA), insect infestation, and mechanical injury. Specifically, overexpression of insectsin poplar plants enhances resistance against two major generalist insects, Mythimna separata and Spodoptera frugiperda. Conversely, suppressing this gene results in a reduced ability of the plants to fend off these insects. At the physiological level, our results indicated that PtrRZFP1 positively regulates leaf surface temperature and the rate of photosynthetic electron transport in poplar plants in response to insect attack. In addition, PtrRZFP1 can upregulate the content of hormones (including ABA, JA, and SA) and lignin in poplar leaves to cope with insects. Transcriptional analysis revealed that PtrRZFP1 activates pathways associated with lignin biosynthesis and JA signaling, thereby contributing to insect resistance. Investigations at the protein level also suggested that PtrRZFP1 may interact with proteins involved in biotic stress responses, mediating the complex dynamics of poplar-insect interactions. Overall, these findings underscore the multifaceted role of PtrRZFP1 in enhancing poplar resistance to generalist insects.

Pennycress is a winter annual intermediate crop with approximately 30% seed oil content suitable for producing biofuels. Here, we evaluated seed development, anatomy, and agronomically relevant traits of a transparent testa 8 knockout mutant (tt8-2bp) generated by CRISPR genome editing to improve seed quality. We performed histochemical analyses on wild-type and tt8-2bp seeds at different developmental stages. No visible anatomical defects were observed in embryos and endosperm of tt8-2bp seeds. However, tt8-2bp seed coats had drastically reduced proanthocyanidins and proanthocyanidin monomers, which correlated with increased seed coat permeability, increased imbibition rates, and altered seed aging of tt8-2bp seeds. A cuticle layer was detected in tt8-2bp and wild-type seed coats. Further analysis is required to assess possible quantitative and structural defects in the tt8-2bp seed cuticle. Based on metabolomic and solid-state nuclear magnetic resonance (NMR) analyses, tt8-2bp seed coats had decreased aromatic compounds and cell wall polysaccharides compared to wild-type seed coats. Consistently, tt8-2bp seeds also had reduced non-embryonic tissue dry weights, increased embryo dry weights, and unchanged total seed weights compared to wild-type seeds. This indicated altered nutrient partitioning during tt8-2bp seed development. The agronomic implications of tt8-2bp altered seed traits on pennycress domestication were discussed in depth.

Gibberellins (GAs) are plant hormones that regulate growth and development. We investigated how a transcription factor, SlBBX20, modulates plant height by affecting GA metabolism and response in tomato (Solanum lycopersicum L.). We found that overexpression of SlBBX20 caused dwarfism, which was rescued by GA treatment, while knockout of SlBBX20 increased plant height. SlBBX20 directly activated the expression of GA metabolic oxidase genes (SlGA2ox1, SlGA2ox4, and SlGA2ox5) and repressed the expression of a GA-responsive gene, SlMYB9. Plants overexpressing SlMYB9 grew taller than wild type and knockout plants after GA treatment, as SlMYB9 inhibited the expression of SlGA2ox4 and SlGA2ox5. Restoring SlMYB9 expression in SlBBX20-overexpressing plants reversed the dwarf phenotype. Our study reveals a novel regulatory module involving SlBBX20-SlMYB9-SlGA2 oxidase for controlling plant height and provides insights into the molecular mechanisms of GA action in plants.

Maize is among the most commonly grown crops worldwide. Infections with Ustilago maydis, causing corn smut disease and leading to loss of biomass, yield, and silage quality, occur in all major growing regions. Rising global temperatures are predicted to reshape crop-pathogen interactions and subsequently threaten yield. However, the impact of minimal temperature changes resulting from climate change, and the molecular basis of temperature-modulated susceptibility, remain poorly understood. To investigate these, U. maydis infection trials and RNA-seq profiling across multiple maize cultivars grown under distinct temperature regimes based on the evaluation of climate data for Bavaria (Germany) were conducted. Even a minimal temperature change enhanced disease symptoms, while a brief heatwave greatly increased tumor formation and accelerated disease development. The observed phenotypic changes were accompanied by broad temperature- and cultivar-defined alterations in the host's transcriptional response. Expression-phenotype correlations, followed by in vivo testing, revealed factors contributing to variation in resistance. GIBBERELLIC ACID STIMULATED TRANSCRIPT-LIKE 4 is a broad resistance factor with implications of germplasm-specific variations in expression. The expression of γ-aminobutyric acid (GABA) transaminases, which cleave GABA, which acts as a susceptibility metabolite during U. maydis infection, is regulated in a temperature- and cultivar-dependent manner and correlated with fewer infections.

Allelic variations in BnaFLC.A10, BnaFLC.A2, and BnaFT.A2 have been associated with flowering time regulation in Brassica napus. However, the effects of their interactions remain insufficiently understood. In this study, we investigated the genetic basis underlying flowering time differences between the winter-type Tapidor and the spring-type Westar. Utilizing quantitative trait locus sequencing (QTL-seq) and transcriptome analysis, BnaFLC.A10, BnaFLC.A2, and BnaFT.A2 were identified as candidate genes associated with flowering time variation. Functional evidence from transgenic ectopic expression and CRISPR/Cas9-mediated genome editing supports their involvement in flowering time regulation. Genotypic and phenotypic analysis of 248 individuals from an (Westar×Tapidor) F2 population, along with 226 B. napus accessions, indicated additive effects of BnaFLC.A10 and BnaFLC.A2 in vernalization requirements and potential epistatic interactions with different BnaFT.A2 alleles. These results provide insights into the genetic interactions underlying flowering time variation and may assist in optimizing allele combinations for enhanced adaptation in B. napus breeding.

Water moves through trees pulled under tension through a series of dead tubes called xylem. During drought, conduits can be invaded by air, causing an embolism, leading to tissue or whole-plant death. Fagus sylvatica is the most abundant European broadleaf forest tree, and is currently under threat due to an increasing frequency and severity of drought, resulting in xylem embolism, dieback, and death. Here, we investigated the variation in embolism resistance across globally distributed individuals of F. sylvatica f. purpurea receiving between 563 mm and 1362 mm of rainfall per year, as well as variation in embolism resistance across the canopy. We found no difference in the water potential when 50% of the stem xylem was embolized (P50) across locations in this clonal form of F. sylvatica but we did find variation in P50 across the canopy driven by light, with shade branches being significantly more vulnerable than part or full sun-adapted branches. The lack of variation in response to annual rainfall in a globally distributed clone has implications for predicting the risk of mortality driven by periodic droughts and long-term shifts in rainfall patterns due to climate change in F. sylvatica. Our work also highlights the importance of horticultural resources such as globally distributed clones as a model system for examining plant responses to the environment.

Drought-induced depletion of non-structural carbohydrates has been reported to affect xylem hydraulic vulnerability, which in turn is frequently correlated with water potential at turgor-loss point. Given that non-structural carbohydrate depletion can impair osmoregulation, we hypothesised that vessel-associated parenchyma cells (VACs) that undergo drought-induced turgor loss and plasmolysis could facilitate gas movement and the formation of xylem embolism. Plasmolysis was induced in wood parenchyma of Populus nigra stems of mature trees and potted plants by radial injection or axial perfusion with a polyethylene glycol solution at low osmotic potential. The effect of polyethylene glycol on embolism resistance was assessed using the gas injection technique followed by classic hydraulic quantification of embolism, as well as with flow-centrifuge measurements. Light and transmission electron microscopy confirmed the occurrence of plasmolysis of VACs in osmotically treated samples, while hydraulic measurements revealed an increase in xylem vulnerability to embolism upon induction of plasmolysis, raising the loss of hydraulic conductivity by ∼20-40%. The results therefore support the hypothesis that the maintenance of cell turgor in VACs is critical for xylem hydraulic integrity under drought. We speculate that plasmolysis of VACs could promote gas movement to functional vessels via vessel-parenchyma pits, increasing the likelihood of embolism propagation.

Cotton fiber elongation is a complex developmental process regulated by hormonal and metabolic signals. Auxin (indole-3-acetic acid, IAA) and brassinosteroid (BR) play crucial roles in cotton fiber development, but the mechanism by which they coordinate to regulate fiber elongation remains unclear. In this study, we determined that IAA levels gradually increase during fiber development and are higher in long-fiber varieties. In vitro ovule culture experiments revealed that IAA promotes fiber elongation in a dose-dependent manner. Transcriptome analysis showed that IAA activates BR biosynthesis and the BR signaling pathway, implying crosstalk between the two hormones. Interestingly, IAA could partially rescue fiber elongation caused by BR deficiency due to brassinazole treatment and in pag1 mutants, and BR supplementation partially alleviated fiber inhibition resulting from impaired IAA transport or IAA deficiency. However, neither hormone fully compensated for the absence of the other, indicating that both serve non-redundant roles in fiber elongation. Additionally, inhibiting glucose signaling by suppressing hexokinase activity through N-acetylglucosamine impaired fiber growth, but this could be rescued by exogenous application of either IAA or BR, suggesting that glucose acts upstream of IAA and BR, which cooperatively regulate the elongation of cotton fibers.

Hybridization and polyploidization combine divergent nuclear genomes with maternally inherited organelles, often disrupting cytonuclear coadaptation critical for respiration and photosynthesis. This review examines the mechanisms, outcomes, and evolutionary significance of cytonuclear incompatibility in plants. We focus on how divergence in nuclear-encoded, organelle-targeted proteins and organelle genomes leads to mismatched interactions in protein import, folding, and assembly of multi-subunit enzyme complexes. The evidence highlights taxon- and complex-specific responses that mitigate incompatibilities, including the biased retention and expression of maternal alleles, gene conversions, and regulatory adjustments. We highlight how cytonuclear compatibility in hybrid lineages entails responses at multiple levels of regulation, including methylation/chromatin accessibility, gene expression, alternative splicing, translation rates, organelle import, protein-folding and assembly, and protein degradation pathways. Manifestations such as chlorosis, seed sterility, or hybrid breakdown underscore their role in shaping reproductive barriers. Conversely, maternal bias and compensatory mechanisms often act to restore functional integration of parental genomes, allowing hybrid and polyploid persistence. Beyond their evolutionary role in speciation and adaptation, cytonuclear incompatibilities underpin key practical applications, notably cytoplasmic male sterility, a cornerstone of hybrid crop breeding. We conclude that cytonuclear dynamics reveal both constraints and opportunities, illuminating plant diversification, hybrid resilience, and agricultural innovation.