Journal of Experimental Botany最新文献

Plant pathogens rely on host-derived nutrients for proliferation, yet the mechanisms by which hosts supply these nutrients remain incompletely understood. Here, we show that infection of Arabidopsis thaliana by the necrotrophic fungus Botrytis cinerea leads to increased accumulation of the amino acid transporter UmamiT20 in leaf veins surrounding the lesions. Functional assays demonstrate that UmamiT20 mediates amino acid transport of a wide range of neutral amino acids. Consistent with a role during infection, umamiT20 knockout mutants displayed significantly reduced susceptibility to B. cinerea. Our findings extend the concept of transporter-mediated susceptibility beyond the SWEET sugar transporters in bacterial blight of rice, cassava, and cotton, to a necrotrophic fungus and implicate nutrients other than sucrose, namely amino acids, in nutrition or nutrient signaling related to immunity. We hypothesize that stacking of mutations in different types of susceptibility-related nutrient carriers to interfere with access to several nutrients may enable engineering of robust pathogen resistance in a wide range of plant-pathogen systems.

The mechanistic aspects of resource availability on carbon allocation to growth or defense of plants has been widely discussed. This study tests the growth-defense trade-off framework by comparing rates of carbon assimilation and secondary metabolite production in novel time scales in N-limited sunflower. Upon exposure to N deficiency, increased accumulation of caffeoylquinic acid derivatives in leaf and root tissue was detected, which, however, represented only a small fraction of the assimilated carbon. Furthermore, there was no increased production of lignin under N limitation. Instead, the 'excess' of assimilated carbon not used for leaf expansion was largely allocated to the roots for vegetative processes. Lastly, an active steering of caffeoylquinic acid biosynthesis was indicated by increased expression of hydroxycinnamoyl CoA:quinate hydroxycinnamoyl transferase 3. Despite a relatively late reduction of the N concentration in the plants, it could not be definitively resolved to what extent changes in the physiological C/N balance may have influenced caffeoylquinic acid formation. Nevertheless, there is no definitive support for the mass-action-based accumulation of secondary metabolites suggested by a traditional view of the growth-defense trade-off framework. One may assume that the correlation of resource availability and defense investment has been shaped by complex evolutionary processes and is coordinated by tightly regulated biochemical networks, although it may be triggered by carbon/nutrient imbalance at the cellular scale.

F-box proteins (FBPs), the substrate-recognition subunits of SCF (SKP1-Cullin1-F-box) E3 ubiquitin ligases, are pivotal regulators of protein turnover and play central roles in shaping cellular signaling dynamics. In plants, the repertoire of FBP-encoding genes has undergone remarkable expansion, giving rise to one of the largest and most functionally diverse protein families in the plant kingdom. This diversification underpins an extensive regulatory capacity, enabling FBPs to modulate processes such as hormone perception, developmental patterning, circadian rhythm, and responses to a wide spectrum of biotic and abiotic stresses. Here, we synthesize recent advances that illuminate the molecular mechanisms governing FBP activity, including insights into substrate recognition and their potential applications.

The cell wall plays a key role in determining mesophyll conductance (gm) and photosynthetic capacity. While the impact of wall thickness (Tcw) on gm is well understood, the influence of wall composition and structural interactions on Tcw and gm remains unclear, and it is unknown whether these factors have been affected during crop domestication. In this study, we examined 25 wild and 13 domesticated Gossypium genotypes to investigate whether variations in Tcw, composition, and structure affected gm and photosynthesis. X-ray diffraction was used to analyze internal cell wall structure. Cotton domestication reduced Tcw by modifying the pectin-to-(cellulose+hemicellulose) ratio and increasing cellulose crystallinity. However, cell wall composition and structure regulate gm differently in wild and domesticated genotypes. In wild genotypes, the pectin-to-(cellulose+hemicellulose) ratio influences CO2 diffusion, while in domesticated genotypes, the pectin matrix may be more compact, making 1/(pectin+cellulose+hemicellulose) a better predictor, reflecting the internal property differences of the cell wall. We suggest that the exceptionally low Tcw values reported in cotton domesticated genotypes indicate that they have reached the lower limit, which may impose physical constraints on component proportions and conformation.

Soil salinity is a major threat to sustainability and profitability of agricultural production systems and food security of future generations. Plants respond to salinity-induced constraints by activating numerous adaptive responses that operate in a strict tissue- and cell-specific manner and require coordination at the whole-plant level. Central to this process is the root-to-shoot signaling. Being the first organ to sense saline conditions in the rhizosphere, roots produce various signals that are then propagated through the plant, enabling the coordination and integration of physiological processes across different organs and tissues. These signals can be of different nature and include physical (electric and hydraulic signals; propagating reactive oxygen species and Ca2+ waves), chemical (hormones, photoassimilates, and nutrients), and molecular (peptides, proteins, and miRNAs) signals. Each category of long-distance signals has its own origin, transport mechanism, target tissue(s), function, and interaction with other signals. In this work, we summarize the current knowledge of such long-distance signaling in plants grown under saline conditions, with a specific focus on halophytes-naturally 'salt-loving' plants. Our aim is to reveal specific signaling traits that confer salinity stress tolerance that can then be used as new targets in breeding programs aimed to improve salinity stress tolerance in crops.

Autophagy is an evolutionarily conserved pathway in eukaryotes that delivers cytoplasmic cargos for vacuolar/lysosomal degradation. Plant pathogens have evolved various strategies to regulate host autophagy for successful infections. However, whether herbivores modulate host autophagy to facilitate feeding remains unclear. Previously, we identified a salivary protein RP246 from Riptortus pedestris, which enhances Spodoptera litura feeding when transiently expressed in Nicotiana benthamiana. This study further revealed that RP246 protein is delivered into the soybean plant during R. pedestris infestation. Targeted gene silencing of RP246 significantly reduced insect feeding duration, honeydew excretion, and body weight, demonstrating that RP246 functions as a virulent effector. Our findings further demonstrated that RP246 interacts with NbATG8 and GmATG8c, the core autophagy protein, using its AIM2 (ATG8-interacting motif2), and subsequently promotes the formation of autophagosomes. RP246-induced insect feeding depends on NbATG8, and treatment with the autophagy inhibitor, 3-methyladenine (3-MA), significantly inhibits R. pedestris feeding on soybean plants. Collectively, these findings revealed that RP246 activates plant autophagy to facilitate R. pedestris feeding by interacting with ATG8. Our findings uncovered a mechanism utilized by herbivores to facilitate infestation through hijacking the autophagy machinery of the plant.

Photosynthesis is a complex sequence of physical, electrochemical, biochemical, and physiological processes that convert light energy and carbon dioxide into sugars. These sugars then provide the energy and carbon backbone for all metabolic pathways involved in plant growth and development. However, if light energy is not managed effectively within the thylakoid membrane, it can destroy the photosynthetic apparatus in an oxygenic environment generated by photosynthesis itself. Effective photoprotection requires a variety of partially overlapping regulatory mechanisms that control energy and electron and proton transport, and induce changes in the molecular, structural, and functional features of the photosynthetic apparatus and the thylakoid architecture. This review focuses on vital regulatory mechanisms and how they cooperate to maintain effective photosynthesis and to protect the thylakoid-embedded photosystems (photosystems I and II) against fatal light-induced damage under fluctuating light conditions. The current understanding of plant light regulation is primarily based on studies conducted under stable laboratory conditions, which limits the physiological relevance of the findings. The need for light regulation is further amplified by its complex interactions with other environmental variables. To bridge the gap between laboratory insights and real-world applicability, new technologies are needed for multi-environmental plant growth and experimentation that leverage artificial intelligence and machine learning.

Pigeonpea (Cajanus cajan L. Millsp.) is a grain legume crop that is crucial for food and nutrition security in the sub-tropical regions of Asia and Africa. However, its production is constrained by undesirable varietal features and susceptibility to biotic and abiotic stresses. There is an urgent need to develop pigeonpea varieties with ideotype combining traits needed by the stakeholders. Landraces and wild relatives of pigeonpea are rich source of genes for genetic advance towards the desired ideotype. Pigeonpea genome and extensive transcriptome data required for gene discovery are available. Simple sequence repeat and single nucleotide polymorphism marker assays have been designed and used in mapping of genes and quantitative trait loci for key traits, but these need to be validated and utilized in breeding. Pigeonpea genetically modified for pod borer resistance is awaiting regulatory approval, and the power of genome editing is poised to be harnessed. Marker-assisted selection is still not a practical reality in pigeonpea, but mapping studies position the crop for future breakthroughs. Marker-assisted selection is expected to play a greater role in accelerating pigeonpea ideotype breeding. This review provides a comprehensive account of stakeholder preferences of varietal traits and genetic and genomic resources to help devise molecular breeding strategies for pigeonpea.

Wheat production is continually threatened by stripe and leaf rust because virulent races rapidly overcome single race-specific genes. Durable, broad-spectrum resistance is needed. Adult plant resistance (APR) provides partial, stable resistance from multiple minor-effect loci acting additively; pleiotropic loci like Lr34/Yr18 and Lr46/Yr29 add durability. We used an elite Australian panel (OzWheat=589) and a diverse landrace panel (Vavilov=295), genotyped with ∼30K SNPs and phenotyped across environments. Linkage disequilibrium partitioning defined 7,659 genome-wide haploblocks. To prioritise robust signals, we ranked haploblocks by haplotype effect variance and examined the top 100 per trait. For stripe rust, 52/100 were significant, with 32 shared across panels; for leaf rust, 50 were significant, 29 also detected in Vavilov. Several intervals co-localised with APR regions (Lr46/Yr29), and one 7BL interval intersected seedling gene Lr14a. To translate mapping into breeding decisions, we developed an introgression fitness index to quantify the value of resistant haplotypes in elite backgrounds. Using elite cultivar Scepter, we applied a genetic algorithm to select 50 donor parents carrying desirable haplotypes. Simulations showed that pyramiding these haplotypes can enhance resistance while maintaining elite genomic background. This study provides practical breeding tools, including haplotype catalogue and a novel selection index to accelerate rust-resistant wheat development.

The flag leaf is a major contributor of photosynthetic assimilates to developing grains. We investigated the genetic architecture and cellular basis of flag leaf length (FLL) and width (FLW) in a multiparent population of 45 recombinant inbred line (RIL) populations (HvDRR) in barley. Fine-mapping of a major quantitative trait locus (QTL) was performed to prepare the isolation of the causal gene. Natural variation of FLL and FLW across environments was highly heritable, and genotypes from warm climates produced longer and wider flag leaves than those from cooler regions. Variation in flag leaf size was quantitatively inherited and influenced by 24 consensus QTLs, of which 17 have not previously been reported. Validation of QTLs qHvDRR-FLS-8 and qHvDRR-FLS-17 in nearly isogenic RILs showed that these QTLs also controlled length and width of leaves older than the flag leaf. The number of epidermal cells primarily determined FLL, whereas the number and size of epidermal cells collectively determined FLW differences. In addition, we identified the previously unknown effect of genic alleles and epialleles at Vrn-H1 on flag leaf size variation in spring barley. Furthermore, we fine-mapped qHvDRR-FLS-8, narrowing the interval from 8.7 Mb to 3.5 Mb. In conclusion, our study identified the genomic regions associated with morphological and anatomical variation for leaf size and set the stage to uncover causal genes.