The Plant Journal最新文献

Plant U-box (PUB) E3 ubiquitin ligases are well known for their diverse functions in plant growth and development through physical link to cell signaling hubs to activate regulatory networks. Brassinosteroid (BR) signaling is negatively regulated by a protein kinase GSK2, which interacts with and phosphorylates OsOFP8 (OVATE family protein 8) to regulate BR signaling. Here we identified OsPUB9, a functional E3 ubiquitin ligase, which acts as a negative factor in BR signaling to regulate leaf inclination angle and grain size in rice. OsPUB9 displays autoubiquitination activity and is degraded in response to BR treatment. Interaction with OsUBC13, a rice E2 ubiquitin-conjugating enzyme, suppresses OsPUB9 degradation. OsPUB9 interacts with GSK2, and the interaction reduces autoubiquitination of OsPUB9. Coexpression of OsPUB9 and GSK2 in rice protoplasts suppresses degradation of OsPUB9 but promotes degradation of GSK2. OsPUB9 also interacts with OsOFP8, a positive regulator in BR signaling, and the interaction suppresses degradation of OsPUB9 but facilitates OsOFP8 degradation. Our study reveals that OsPUB9, GSK2, and OsOFP8 form a regulatory network in BR signaling to mediate gene expression, leaf angle, and grain size in rice.

Histone modifications play critical roles in plant growth and development. Crossing-over (CO) during meiosis, which constitutes a fundamental process ensuring sexual transmission of genetic material to the next generation and, meanwhile, generating diversity within species by creating new chromosome/allele combinations, occurs predominantly in euchromatin, which is enriched in active histone marks such as H3K4me3, H3K36me3, and H2Bub1. In plants, it is known that CO hotspots are correlated with H3K4me3 but the role of H3K36me3 and H2Bub1 during meiosis remains elusive so far. Here, we studied the Arabidopsis (Arabidopsis thaliana) sdg8-1 and hub2-2 mutants impeded in depositing H3K36me3 and H2Bub1, respectively. Chromosome spreading using 4′,6-diamidino-2-phenylindole (DAPI) staining indicated that male meiotic stages are defective in the sdg8-1 mutant, and the defect increases synergistically in the sdg8-1hub2-2 double mutant. Defects in meiosis, seed formation, and silique length were also observed by RNAi-knockdown of SDG8 using the meiosis-specific gene DMC1 promoter. This corroborates to support a bona fide role of active histone marks during meiosis and plant reproduction. Using the tetrad-based visual reporter lines and immunostaining with antibodies against HEI10 and ZYP1, it was found that synapsis and pairing of homologous chromosomes are abnormal and CO rate increases in sdg8 mutants, pointing to a repressive role of SDG8 in Arabidopsis male meiotic homologous recombination.

Cell survival depends on the maintenance of cell homeostasis that involves all the biochemical, genomic and transport processes that take place in all the organelles within a eukaryote cell. In particular, ion homeostasis is required to regulate the membrane potential and solute transport across all membranes, any alteration in these parameters will reflect in the malfunctioning of any organelle, and consequently, in the development of the organism. In plant cells, sodium transporters play a central role in keeping the concentrations of this cation across all membranes under physiological conditions to prevent its toxic effects. HKT transporters are a family of membrane proteins exclusively present in plants, with some homologs present in prokaryotes. HKT transporters have been associated to salt tolerance in plants, retrieving any leak of the cation into the xylem, or removing it from aerial parts, including the flowers, to be transported to the roots along the phloem. This function has been assigned as most of the HKT transporters are located at the plasma membrane. Here, we report the localization of the HKT from Physcomitrium patens to the thylakoid membrane, reminiscent of the prokaryote origin of these family of transporters. Mutation of PpHKT leads to several alterations in the phenotype of the organism, including the lack of sporophyte formation, and changes in expression of many genes. These alterations suggest that the breakdown in chloroplast ion homeostasis triggers a signalling cascade to the nucleus to communicate its status, being important for the moss to complete its life cycle.

Plants are constantly challenged by a diversity of abiotic stressors, and growth arrest is a common plant response aimed at enhancing stress tolerance. Because of this growth/stress tolerance antagonism, plants must finely modulate their growth and responses to environmental stimuli. Here, we demonstrate that HSFB1, a heat shock transcription factor, plays a critical role in the coordination of plant growth and drought stress responses in Arabidopsis thaliana. First, we found that HSFB1 negatively regulates plant growth and development under normal conditions and that HSFB1 expression is enhanced under drought stress. Conversely, the loss-of-function mutant hsfb1 exhibited increased plant growth and reduced drought stress tolerance compared with the wild-type. Consistently, overexpression of HSFB1 suppressed plant growth and enhanced drought stress tolerance. Subsequently, via chromatin immunoprecipitation sequencing, RNA sequencing, and transient expression assays, we screened and identified the heat shock protein 101 (HSP101) gene as a direct transcriptional target of HSFB1. Genetic analysis suggested that HSP101 functions downstream of HSFB1 to positively regulate drought tolerance in plants. Furthermore, we found that HSFB1 physically interacts with the eukaryotic translation initiation factor eIF3G1, and this interaction appears to be further enhanced under drought stress. Notably, the mutation of eif3g1 increased the severity of drought-induced growth inhibition in the hsfb1 mutant, and eIF3G1 enhanced the transcriptional activation of HSFB1 on the HSP101 promoter under drought stress. Altogether, our findings highlight HSFB1 as a key regulator coordinating plant growth and drought stress responses in Arabidopsis.

To explore the proteomic regulation that underlies the physiological, anatomical, and chemical characteristics of wood in acclimation to changing light and nitrogen (N), saplings of Populus × canescens were treated with control or high irradiance in combination with low, control or high N for 4 months. High irradiance led to elevated levels of starch, sucrose, glucose, and fructose, decreased concentrations of ammonium, nitrate, most amino acids and total N, wider xylem, more xylem cell layers, narrower vessel lumina, longer fiber cells, greater fiber wall thickness, and more cellulose and hemicellulose but less lignin deposition in poplar wood. Limiting N resulted in increased levels of starch and sucrose, reduced levels of glucose, fructose, ammonium, nitrate, amino acids and total N, narrower xylem, fewer xylem cell layers, reduced vessel lumen diameter, thicker fiber walls, and less cellulose and more hemicellulose and lignin accumulation, whereas high N had the opposite effects on poplar wood. Correspondingly, numerous differentially abundant proteins, which are related mainly to the metabolism of carbohydrates and amino acids, cell division and expansion, and deposition of secondary cell walls, such as sucrose synthase 6 (SUS6), cell division cycle protein 48 (CDC48) and laccases (LACs), were identified in poplar cambiums in response to changes in light intensity and N availability. These results suggest that proteomic relays play essential roles in regulating the physiological characteristics and anatomical and chemical properties of poplar wood in acclimation to changing light and N availabilities.

Acetylation modifies protein subcellular localization, stability, enzymatic activity, and protein–protein and protein-DNA interactions, playing a crucial role in mediating protein function. However, research on non-histone acetylation remains limited. This study investigates changes in lysine acetylation (Kac) in proteins of birch (Betula platyphylla) in response to drought using 4D label-free quantitative lys-acetylproteome analysis. We identified a total of 15 064 acetylated peptides across 4393 proteins, with 2486 Kac sites exhibiting significant changes: 246 prteins showed increased Kac levels, while 1406 displayed reductions. Notably, proteins associated with metabolic pathways, such as nucleotide sugar biosynthesis, proteasome, glutamate decarboxylase and the tricarboxylic acid (TCA) cycle, were significantly impacted. The alterations in Kac levels correlated with various KEGG pathways, suggesting that acetylation plays a regulatory role in drought response mechanisms. Furthermore, we identified specific acetylation sites in transcription factors (TFs), highlighting their involvement in this process. Functional validation demonstrated that mutations in Kac sites of five randomly selected TFs resulted in significant changes in drought tolerance, emphasizing the critical role of lysine acetylation in modulating stress responses. Overall, our findings indicate that Kac modification serves as a key regulatory mechanism in birch adaptation to drought stress, influencing both metabolic processes and transcriptional regulation.