The Plant Journal最新文献

Abscisic acid (ABA) plays a crucial role in enforcing seed dormancy and suppressing germination under stress conditions by stabilizing key transcriptional repressors. However, the mechanisms by which plants actively attenuate this repression to resume developmental growth remain largely unclear. In this study, we identify chloroplast vesiculation (CV) as a negative regulator of ABA signaling in Arabidopsis. Silencing of CV resulted in hypersensitivity to ABA during seed germination and stomatal closure, whereas its overexpression conferred ABA insensitivity. We demonstrate that CV physically interacts with and directly promotes the vacuolar degradation of two key positive regulators of ABA signaling—the transcription factor ABI5 and the WD40-repeat protein XIW1. Genetic epistasis analyses confirmed that ABI5 and XIW1 function downstream of CV, as loss-of-function mutations in either ABI5 or XIW1 suppressed the ABA-hypersensitive phenotype of CV-silenced plants. Furthermore, we found that ABA itself negatively regulates CV at both the transcriptional and post-translational levels, forming a feedback loop that fine-tunes ABA sensitivity. Our study thus uncovers a previously unknown regulatory module in which CV attenuates ABA responses by targeting ABI5 and XIW1 for vacuolar degradation, thereby facilitating the transition from seed dormancy to germination.

The pedicel plays a crucial structural and physiological role in connecting fruits to plants, facilitating the transport of photosynthates essential for fruit development. Pedicel length (PL) significantly influences fruit growth, harvesting efficiency, and postharvest handling. However, the genetic basis of PL in tomato remains poorly understood. In this study, we integrated genome-wide association studies and bulked segregant analysis to identify a high-confidence loci TPL3 (Tomato Pedicel Length 3), which harbors a cluster of six Expansins (EXPs) that regulate pedicel elongation from flower to red ripe fruit. Homozygous mutants harboring various combinations of EXP gene mutations were generated using CRISPR/Cas9. Analysis of PL in exps mutants revealed that the EXPs cluster regulates pedicel elongation in both the cortex and pith cells throughout reproductive stages, with dose-dependent effects. Biochemical and transcriptomic analyses showed reduced cellulose content, increased cellulase expression, and altered expression of lignin biosynthesis and cell wall remodeling genes in exps pedicels. These findings highlight the role of the EXPs cluster in regulating cell wall composition and structure, ultimately affecting pedicel elongation. Phenotypic correlations further revealed a coordinated relationship between PL and reproductive organ development, including a positive association with fruit weight. Population genetics analyses detected strong selection signatures at TPL3 during evolution by hitchhiking with fw3.2. Using natural variation at indel_5 (ch03_65074685), we developed a molecular marker for PL that achieved 94.2% genotyping efficiency across 120 tomato accessions and exhibited high utility for distinguishing PL phenotypes in commercial cultivars. This study reveals the genetic basis of pedicel elongation and offers an efficient molecular marker for breeding tomatoes with optimized PL.

Comparing closely related species with differing abiotic stress tolerances can reveal physiological and genetic mechanisms that underlie environmental adaptations. Mangroves, found primarily in tropical and subtropical coasts, are expanding poleward due to rising minimum temperatures, for which species-specific cold tolerance likely influences expansion limits. In the Indo-West Pacific, Kandelia obovata tolerates chilling temperatures below 10°C, while its sister species, Kandelia candel, is highly sensitive to chilling and restricted to tropical regions. The discrepancy in chilling tolerance offers unique materials for understanding chilling tolerance mechanisms. This study compares chilling-induced changes in photochemical efficiency, enzymatic activity and gene expression between the two species to reveal their differences in photoprotective strategies. We specifically focus on the impact of chilling on the light reactions of photosynthesis as one of the primary impacts of chilling on plant species is chilling-induced photoinhibition. Despite maintaining higher photochemical efficiency, K. obovata exhibited greater reactive oxygen species (ROS) levels and lower antioxidant enzyme activity than K. candel during chilling at 10°C. Furthermore, interspecies comparison of the expression of genes involved in photoprotection during chilling stress revealed differential expression of PGR5 and CHL, which regulate cyclic electron flow and non-photochemical quenching. The upregulation of these genes in K. obovata and their downregulation in K. candel suggest that differences in photoprotective responses may contribute to the contrasting chilling tolerances of these species. These findings highlight a potential mechanism that contributes to the cold tolerance and biogeographical distributions of subtropical and tropical plant species, emphasizing the need for further comparative studies across a broader range of taxa.

Actinidia spp. (kiwifruit) are functionally dioecious with separate male and female individuals that exhibit a subtle difference in flowering time. However, this sexually dimorphic trait, along with its evolutionary history and the role of sexually antagonistic selection, remains to be fully understood. To investigate the underlying causes of this dimorphism at the genus level, we conducted a comparative pan-genome analysis of two representative kiwifruit species, Actinidia chinensis and Actinidia eriantha, using 10 chromosome-scale genome assemblies from six distinct male and female genotypes. The construction of the pan-genome revealed a total of 52 774 non-redundant pan-gene orthogroups comprising 42 370 gene clusters and 10 404 unassigned genes. Building on this, the comparative analysis further identified 657 syntenic gene sets belonging to 595 pan-gene orthogroups that exhibit significant inter-sexual divergence. It is plausible that they are drivers of the antagonistic selection responsible for conserved sexually dimorphic traits across the extant kiwifruit species. One of these genes is Y-linked FT (YFT), a male-specific variant of FLOWERING LOCUS T that originated following the recent whole-genome duplication event. We demonstrate that A. eriantha YFT is able to promote flowering, suggesting that it may contribute to the sexual dimorphism in kiwifruit flowering time. Notably, YFT is located in the sex-determining region (SDR), with linkage to the sex-determining genes, facilitating its spread in natural populations and SDR's expansion on the Y chromosome. For ease of use and analysis, the entire comparative pan-genome workflow was integrated into a custom Perl script, SynPanScan. This approach helps decipher the genetic basis of flowering sexual dimorphism in kiwifruit and establishes a synteny-based comparative pan-genomic framework for investigating the heritable architecture of natural phenotypic variation.

Tea plants are susceptible to drought stress, with significant impacts on growth, development, and quality. Lignin plays a critical role in tea plants' drought tolerance, while the underlying molecular mechanisms remain largely unexplored. In this study, we found that CsmiR408 was significantly downregulated under drought stress in tea plants, and its expression trend exhibited a significant negative correlation with changes in lignin content. Overexpression of CsmiR408 significantly reduced lignin levels and compromised drought tolerance in transgenic Arabidopsis and tea plants. Meanwhile, our results showed that CsLAC13, as the target gene of CsmiR408, positively regulated lignin accumulation to enhance drought tolerance in tea plants. In addition, we found that drought stress induced the expression of CsMYB44 and CsMYB73, which bind to MBS1 and MBS2 cis-elements in the CsmiR408 promoter to suppress the expression of CsmiR408. Similarly, overexpression of CsMYB44/73 can increase the drought tolerance of tea plants by facilitating lignin biosynthesis. Furthermore, overexpression of CsMYB44/73 suppressed the expression of genes in the flavonoid biosynthetic pathway, leading to a significant reduction in catechin, which indirectly increased the accumulation of lignin. In conclusion, our study proposes a multilevel regulatory module, CsMYB44/73-CsmiR408-CsLAC13, that enhances the drought tolerance of tea plants by promoting lignin accumulation. These findings provide important insights into the molecular mechanisms of drought stress response in tea plants and offer a theoretical basis for breeding drought tolerance varieties.

Flowering is a crucial developmental process in angiosperms. However, the underlying mechanisms remain to be elucidated. In this study, we identify INDETERMINATE DOMAIN (IDD) transcription factors (TFs), IDD14, IDD15, and IDD16, as redundant negative regulators of flowering time in Arabidopsis. The idd14-1 idd15-5 idd16-1 triple mutant displays early flowering, while the gain-of-function mutation in idd14-1D results in delayed flowering under long-day conditions. Gene expression analysis shows that the florigen gene FLOWERING LOCUS T (FT) is activated in idd14-1 idd15-5 idd16-1 but suppressed in idd14-1D. Further analyses show that IDD14 could directly bind to the promoter of FT to suppress its expression. Moreover, IDDs interact with DELLAs in vitro and in vivo, and DELLAs enhance the inhibition ability of IDD14 on FT. Genetic and physiological analyses further support that IDDs regulate flowering through their dependence on FT and are partially involved in DELLA-mediated flowering time regulation. Taken together, our findings suggest that a subfamily of IDD TFs may function as new components of DELLA-mediated gibberellin signaling to negatively modulate flowering time by repressing the expression of FT.

Fruit ripening is a complex process involving physiological and biochemical changes that are influenced by multiple factors. NAC transcription factors play roles in regulating plant growth, development, and responses to plant hormones, and have been implicated in playing regulatory roles in the ripening of several fruits. However, the mechanisms whereby NACs regulate ripening and quality formation in the climacteric fruit apricot (Prunus armeniaca L.) remain unclear. In this study, we identified ripening-associated PaNAC64 from apricot fruit by WGCNA and RT-qPCR analysis and showed that it is upregulated during fruit ripening and is highly expressed at fruit maturity. Expression experiments confirmed that PaNAC64 can promote fruit ripening and the development of fruit quality attributes. PaNAC64 is not induced by exogenous ABA but its expression is significantly enhanced by ethylene. Through correlation analysis, we found that PaCYP707A is negatively correlated with PaNAC64. Experiments confirmed that PaNAC64 directly inhibits the transcription of PaCYP707A, thereby suppressing the hydroxylation-mediated inactivation of ABA, leading to the accumulation of endogenous ABA, which in turn promotes ethylene synthesis and fruit ripening. Our study demonstrates the importance of the interactions between transcription factors, ABA and ethylene in the regulation of apricot fruit ripening, quality formation, and post-harvest storage.