生命科学最新文献

The ubiquitin-proteasome pathway plays a crucial role in plant abiotic stress responses by regulating protein stability. Our previous work demonstrated that the pepper bZIP transcription factor CaADBZ1 regulates abscisic acid (ABA) signaling and drought stress responses. However, the regulatory factors controlling CaADBZ1 protein stability remain unknown. Here, we performed a yeast two-hybrid assay to identify the E3 ubiquitin ligase involved in regulating CaADBZ1 stability. The pepper RING-type E3 ligase CaAIAR1 (Capsicum annuum ABA-Induced Ankyrin repeat RING-type E3 ligase 1) interacts with CaADBZ1 both in vitro and in vivo. CaAIAR1 ubiquitinates CaADBZ1 and exhibits E3 ligase activity that depends on its RING domain. A cell-free degradation assay revealed that CaADBZ1 was unstable under non-stress conditions, and CaAIAR1 accelerated its degradation via the 26S proteasome pathway. CaAIAR1 expression was significantly induced by various abiotic stresses and was associated with altered phenotypic responses to drought stress and exogenous ABA treatment. Moreover, CaAIAR1-silenced pepper plants exhibited enhanced drought tolerance compared to control plants, as evidenced by reduced transpiration rates and increased ABA sensitivity in leaves. Conversely, CaAIAR1-overexpressing Arabidopsis plants showed decreased drought tolerance compared to control plants and exhibited reduced ABA sensitivity at the seedling stage. In addition, co-silencing CaAIAR1 and CaADBZ1 increased drought sensitivity, producing a phenotype opposite to that of CaAIAR1 silencing alone, indicating that CaAIAR1 functions upstream of CaADBZ1 in drought stress. Collectively, our findings suggest that CaAIAR1 negatively regulates the drought response and ABA signaling by modulating CaADBZ1 protein stability.

Plants are simultaneously exposed to multiple abiotic stresses, yet how opposing epigenetic signals are integrated remains unclear. Here, we investigated the combined effects of heat stress and phosphate deficiency in Arabidopsis thaliana, two conditions with antagonistic impacts on DNA methylation. Using an integrated multi-omic approach (WGBS, RNA-seq and small RNA-seq) in roots and shoots under field-mimicking conditions, we show that combined stress establishes a distinct, non-additive epigenomic state characterised by widespread CHH hypomethylation and differential engagement of RdDM and CMT2 pathways. Despite extensive methylation remodelling across transposable elements, genes and intergenic regions, we observe a genome-wide decoupling between DNA methylation dynamics and transcriptional output. Notably, differentially methylated regions are enriched in transcription factor binding sites, particularly GATA motifs, linking CHH hypomethylation to increased chromatin accessibility and activation of GATA-associated regulatory networks. In contrast, nuclear mitochondrial DNA insertions represent a notable exception, where CHH hypomethylation is directly coupled to transcriptional activation. Functional analyses reveal distinct contributions of RdDM and CMT2 to basal silencing and stress responsiveness at these loci. Overall, our results support a model that positions DNA methylation as a regulator of regulatory potential rather than a direct determinant of transcription under combined stress.

Follicular helper T (Tfh) cells orchestrate germinal center (GC) derived humoral immunity by providing essential help to B cells. Despite their key role in humoral immunity, the metabolic cues that shape Tfh cell differentiation and functions in humans remain poorly understood. Here, using a human ex vivo Tfh cell differentiation model, we investigated the metabolic requirements of Tfh cell development and function through targeted metabolic perturbation of glycolysis and fatty acid metabolism, transcriptomic analyses, and metabolic rescue experiments. Unexpectedly, early glycolytic inhibition enhanced Tfh cell differentiation but markedly impaired function, including reduced IL-21 production and diminished B-cell help. Transcriptomic and metabolic analyses revealed that glycolytic inhibition was accompanied by suppression of fatty acid metabolism. Consistently, independent inhibition of fatty acid synthesis or oxidation suppressed Tfh cell help functions, including IL-21 and IFN-γ production, as well as B-cell help potential. Interestingly, acetate supplementation partially restored IFN-γ secretion in glycolysis-inhibited conditions, but not IL-21, indicating limited metabolic compensation. Together, these findings reveal distinct metabolic requirements for Tfh cell differentiation and function and identify glycolysis-dependent fatty acid metabolism as an important determinant of human Tfh cell functional competence. This metabolic crosstalk provides new insight into the regulation of Tfh cells and Tfh-driven humoral immunity in vaccination and autoimmunity.

The wound healing process in postharvest citrus fruit represents a crucial physiological mechanism that effectively resists external stress and minimizes quality deterioration. Nevertheless, the molecular mechanisms involved in wound healing by GATA transcription factors in citrus remain largely unexplored. In this research, CsGATA5 was characterized as a newly identified transcriptional activator promoting wound healing in citrus fruit. Transient overexpression of CsGATA5 in tobacco also confirmed its role in promoting suberin accumulation. Gene expression and metabolite profiling analyses following CsGATA5 overexpression revealed that CsGATA5 activated pathways associated with amino acid metabolism during wound healing. DLR, EMSA, ChIP-qPCR, and Y1H assays demonstrated that CsGATA5 bound to the promoter regions of target genes in tryptophan metabolism (CsTRYS and CsTDC2), thereby activating their expression. Notably, the activation of CsTRYS and CsTDC2 genes during citrus wound healing contributed to the subsequent induction of downstream suberin biosynthesis. Moreover, the exogenous treatment of key metabolites of the amino acid pathway, including tryptophan, 5-hydroxytryptamine, and phenylalanine, significantly promoted wound healing and further supported a potential regulatory cascade of tryptophan metabolism– tricarboxylic acid cycle– suberin biosynthesis. This study sheds light on the molecular regulatory network by which GATA transcription factors modulate wound healing in fruit.