Journal of Experimental Botany最新文献

Tonoplast sugar transporters are key regulators of intracellular sugar partitioning, mediating sugar flux between the cytosol and vacuole-an essential process for plant development and stress adaptation. Recent advances have deepened our understanding of well-characterized transporters such as TSTs and SWEETs, while also expanding the transporter repertoire with newly identified members including SWEET2, ERDL4, and SFP1/SAST1 across diverse plant species, including crops. Despite these insights, the regulatory mechanisms controlling transporter activity remain largely unresolved. This review aims to consolidate this expanding body of knowledge and explore in greater depth the molecular regulatory mechanisms controlling tonoplast sugar transporters. Additionally, we also analyze publicly available expression datasets to evaluate the potential of these transporters as targets for improving plant resilience under climate change conditions, particularly in response to elevated atmospheric CO2. Ultimately, this review presents a new perspective on the significance of studying tonoplast sugar transporters, aiming to develop innovative strategies that enhance plant resilience to environmental challenges.

Chloroplasts are semi-autonomous organelles essential for photosynthetic organisms. They derived from ancestral cyanobacteria through an endosymbiotic event. In plants, these organelles are inherited as non-photosynthetic plastids, the proplastids, which can differentiate into chloroplasts or other specialized types of plastids in response to external and internal signals and cues, and following precise developmental programmes. Transcriptional regulation of chloroplast biogenesis and, to a lesser extent chromoplast differentiation, has been a central focus of interest, leading to the identification of several key factors. This review highlights recent research on transcription factors and epigenetic modifiers that regulate chloroplast biogenesis, the evolution of transcriptional regulation in land plants, and factors regulating chromoplast differentiation. However, significant knowledge gaps remain regarding plastid differentiation in specific tissues and species, as well as the biogenesis of other plastid types. Thus, the review highlights the complexity of chloroplast biogenesis, and open questions on spatial and temporal regulation, lineage- and species-specific mechanisms, and biogenesis of diverse plastid types. Understanding this process will advance basic plant biology but also holds biotechnological potential to address present and future challenges.

In Arabidopsis thaliana, HEAT-INTOLERANT 4 (HIT4) mediates heat-induced chromocenter decondensation, a process essential for plant thermotolerance; however, its molecular regulation remains unclear. Using TurboID-based proximity labeling, bimolecular fluorescence complementation, and pull-down assays, we observed that PUB49 directly interacts with HIT4. PUB49 is a nuclear protein possessing both U-box E3 ubiquitin ligase and peptidyl-prolyl isomerase domains. CRISPR/Cas9-generated pub49 knockout mutants exhibited heat-sensitive phenotypes like those of the hit4-1 missense mutant. Subnuclear localization analysis revealed that the PUB49-HIT4 complex localizes to chromocenters under normal conditions and relocates to the nucleolus before chromocenter decondensation in response to heat stress. In contrast, the PUB49-HIT4S227Y complex formed numerous granules throughout the nucleus, independent of temperature. These results, suggest that functional HIT4 is required for temperature-dependent subnuclear trafficking of PUB49. Furthermore, chromocenter decondensation was incomplete in pub49 mutants under heat stress. Complementation analysis demonstrated that only the U-box domain, rather than peptidyl-prolyl isomerase, was sufficient to restore full chromocenter decondensation and thermotolerance. These findings demonstrate that nuclear U-box E3 ubiquitin ligase is involved in heat-responsive chromatin remodeling and HIT4-mediated thermotolerance.

Cross-kingdom RNAi (ck-RNAi) is a biological process in which small RNA (sRNA) molecules are transferred between organisms belonging to different kingdoms to silence specific genes. Although numerous instances of reciprocal ck-RNAi have been documented in plants, demonstrating a modulation of the interaction between plants and their pathogens, pests, or symbiotic partners, the underlying molecular mechanisms remain largely elusive. In this review, we distinguish between naturally occurring and transgene-based cases of ck-RNAi, examine the diverse mechanisms governing the transfer of primary ck-RNAi signals from donor to recipient organisms, and explore the prerequisites for their amplification and systemic spread. Finally, we highlight key unresolved questions concerning the mechanistic basis of ck-RNAi and offer a perspective on its potential role in co-evolutionary dynamics.

Organ chirality in plants has been linked to cytoskeletal organization, as demonstrated in Arabidopsis twisted mutants, where left-skewed cortical microtubules are associated with right-handed twisting, and vice versa. While this phenotype seemingly mirrors vining habits, the hypothesis remains understudied within naturally twining plants. Qualitative observations have identified skewed microtubules in the twining stem of Ipomoea nil (L.) Roth vine, suggesting parallels with Arabidopsis studies. To further investigate organ chirality in twining plants, we used common bean vine (Phaseolus vulgaris L.) to examine the relationship between microtubule orientation, cell morphogenesis, and the right-handed twining phenotype via immunolabeling techniques. Here, we report a transition from mixed microtubule orientations in emergent and elongating internodes to a predominance of longitudinal microtubules in straight and twined stem segments post-elongation. Additionally, we report a distinction in epidermal cell shapes, where straight portions of the stem consist of lobes with rectangular cells and furrows with round cells, while twined portions comprise cells that are relatively more rectangular and stretched. We propose that these orientations reflect dynamic microtubule responses to external stimuli and growth cues, such as tensile stresses from climbing or tissue expansion. Taken together, these findings highlight dissimilarities between twisting Arabidopsis mutants and naturally twining plants.

Lateral root (LR) development in Arabidopsis thaliana requires precise coordination of pericycle founder cell (FC) specification, patterning, and morphogenesis. While auxin signalling is well established in this process, the role of membrane phospholipid signalling-particularly of phosphoinositides-remains less understood. Here, we investigate the contribution of the anionic phospholipids phosphatidylinositol 4-phosphate (PI4P), phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2], and phosphatidylserine (PS) to LR formation using live-cell biosensors, genetic mutants, and inducible lipid depletion tools. We show that PI4P is uniformly distributed throughout lateral root primordia (LRPs), whereas PI(4,5)P2 is specifically depleted in the proliferative core during early LRP development. Time-lapse imaging revealed stable PI4P and PI(4,5)P2 levels before and after FC activation, while PS increased rapidly post-activation. In xylem-pole pericycle (XPP) cells, PI(4,5)P2 decreased and PS increased following LR initiation, with both changes occurring in a membrane domain-specific manner. Genetic analysis of the pip5k1pip5k2 double mutant, deficient in PI(4,5)P2 synthesis, revealed impaired LR initiation and emergence. Conversely, inducible depletion of PI(4,5)P2 using the iDePP system promoted FC specification and accelerated LRP morphogenesis. These results suggest that PI4P functions as a stable basal phospholipid, whereas PI(4,5)P2 and PS undergo dynamic, spatially regulated changes that are critical for LR development. Notably, PI(4,5)P2 acts as a negative regulator of LRP initiation and morphogenesis. Our findings highlight how phospholipid signalling, in coordination with hormonal cues, provides spatial and temporal control over pericycle cell behaviour and lateral root organogenesis.

The strategic Middle Eastern crop date palm is severely threatened by Fusarium proliferatum DSM106835 (Fp), the fungus causing sudden decline syndrome. To decipher the molecular basis of this interaction, we performed a time-series RNA-seq analysis to elucidate the dynamic transcriptomic responses in date palm roots and shoots to Fp infection at 4, 8, and 16 days post-infection (dpi). Thousands of genes showed altered expression, increasing dramatically over time: 4062 and 2741 differentially expressed genes in roots and shoots, respectively, at 4 dpi, rising to 10 670 and 4781 at 8 dpi, and 19 092 and 8570 by 16 dpi. The infection activated core defense pathways, including pathogen-triggered immunity and effector-triggered immunity, and key responses involved reactive oxygen species accumulation, cell wall remodeling, impaired photosynthesis, and reprogramming of hormone signaling pathways for ethylene, jasmonic acid, abscisic acid, and salicylic acid. Changes occurred in primary and secondary metabolism, covering carbohydrates, amino acids, lipids, and phenylpropanoids. Weighted gene co-expression network analysis identified tissue-specific gene modules and critical hub genes associated with Fp responses. This comprehensive analysis provides novel insights into date palm defense mechanisms against Fp infection. The identified key pathways and genes form a crucial foundation for targeted breeding or biocontrol strategies to enhance resistance against sudden decline syndrome.

Breeding elite apple cultivars with scab resistance is a key global goal, as reliance on fungicides is unsustainable. The causal fungus, Venturia inaequalis, evolves rapidly, threatening cultivars with single-gene resistance. Since the 1980s, breeding programmes have introduced novel resistance sources via backcrossing. Here, we generated a haplotype-phased genome assembly of Russian apple R12740-7A and an Oxford Nanopore assembly of the Rvi2-resistance accession TSR34T15, enabling detailed dissection of the Rvi2 resistance locus. Fine-mapping using a 'Royal Gala' × TSR34T15 segregating family delimited Rvi2 to a narrow genomic interval, within which we identified a 10 041 bp long terminal repeat retrotransposon (LTR-RT) insertion-an insert-based structural variant (SV) strongly linked with Rvi2. Notably, this LTR-RT harbours an FPPS gene, a member of the farnesyl pyrophosphate/geranylgeranyl pyrophosphate (FPP/GGPP) synthase family, located 2 kb from a key candidate defence gene. Although the FPPS gene exhibits stable expression, its integration within the retrotransposon suggests a cis-regulatory role, potentially priming adjacent defence genes for robust up-regulation upon pathogen attack. We validated the marker derived from this SV in diverse germplasms and successfully implemented it in marker-assisted selection across extensive seedling cohorts. This marker will streamline the development of scab-resistant apple varieties.

Purslane is a valuable medicinal and edible plant with broad environmental adaptability, resulting in extensive germplasm diversity worldwide. This genetic diversity manifests not only in morphological traits but also in varying levels of resistance to aphid infestation. In this study, we conducted a field survey of aphid populations on 99 purslane accessions and performed controlled inoculation experiments to identify two accessions with extreme differences in aphid resistance: accession no. 66 (HS, highly susceptible) and accession no. 119 (HR, highly resistant). Behavioral assays revealed that aphids preferred feeding on the HS accession and exhibited higher reproduction rates. Comparative transcriptome analysis between the two accessions revealed significant enrichment of genes involved in the monoterpenoid biosynthesis pathway. Non-targeted metabolomic profiling further demonstrated that the levels of two monoterpenoid compounds, d-limonene and myrcene, differed significantly between the HS and HR accessions. Integrated transcriptomic and metabolomic analyses identified two terpene synthase (TPS) genes, PolA01G018740 and PolB01G006810, whose expression levels were strongly correlated with the differential accumulation of d-limonene and myrcene. The differential expression of these TPS genes probably underlies variations in monoterpene content that contribute to aphid deterrence. Our findings provide molecular and biochemical insights into the mechanisms of aphid resistance in purslane and identify candidate genes for breeding insect-resistant cultivars.