Arabidopsis ALA3 plays a key role in the inverted-cone distribution of phosphatidylserine at the pollen tube tip, and phosphatidylserine is crucial for the dist

Heat shock protein 70 (Hsp70) is a class of HSPs involved in plant growth and development, stress response and regulation. The Hsp70 proteins exist widely in the plant world, but the detail information about Hsp70s is still unclear in cucumber. Based on the available cucumber genome, a total of 12 Hsp70 genes (CsHsp70-1 to CsHsp70-12) were identified in this study, and they were distributed among five out of seven chromosomes. The CsHsp70s were divided into four groups based on a phylogenetic analysis by using protein sequences from cucumber and other plants, and their conserved motifs were relatively conserved. Gene duplication analysis showed that segmental duplication is the main driving force of expansion in cucumber CsHsp70 genes. Promoter analysis of CsHsp70 genes showed that they contained many cis-acting elements involved in hormone and stress responses. Expression analysis by RNA-seq and qRT-PCR indicated that the expression of most CsHsp70 genes was associated with multiple biotic and abiotic stresses in cucumber. This study introduces the characteristics of cucumber CsHsp70 genes and the regulation of their expression levels in various abiotic and biotic stresses, which provided a basis for functional exploration and utilization of CsHsp70 genes in the future.

Leaf color mutants are the ideal materials to study the regulation mechanisms of chlorophyll biosynthesis and chloroplast development or as markers for crop breeding. In this study, we identified a virescent true leaf mutant se59 from the ethyl methane sulfonate (EMS)-induced mutant lines of cucumber (Cucumis sativus L.). The se59 mutant showed normal cotyledons, but the true leaf displays light green at early growth stage, which can recover normal green later. The se59 locus was controlled by a single recessive nuclear gene. The grana stacking in the chloroplasts of se59 decreased significantly, and both the photosynthetic ability and the photosynthetic pigment contents of the se59 were significantly lower than those of wild type. The results of BSA-seq and genotyping showed that an Invertase/Pectin Methyl Esterase Inhibitor (INV/PMEI) protein encoded by CsSE59 is a candidate gene for the virescent true leaf mutant. The expression level of CsSE59 in stem, leaf and root is high. Based on the transcriptome analysis of the first true leaf of se59 mutant, the expression levels of 17 leaf color related genes changed significantly, suggesting CsSE59 may regulate virescent true leaf by interacting with some of these genes in cucumber. The identification of CsSE59 is helpful to clarify the role of INV/PMEI in chloroplast development and to understand the mechanisms of leaf color variation in cucumber.

Chloroplast division, a process tightly linked to the energy demands of plants, is initiated by the formation of the stromal filamenting temperature-sensitive Z (FtsZ) ring. The Z ring is highly dynamic, and its constriction provides the essential force for chloroplast division. However, the regulatory mechanisms governing Z-ring dynamics and constriction remain poorly understood. Here, we report that the chloroplast inner envelope membrane (IEM) protein ACCUMULATION AND REPLICATION OF CHLOROPLASTS6 (ARC6) interacts with the chloroplast stromal protein ARC3, and this interaction is negatively regulated by the conserved J-like domain of ARC6. ARC3 is found both distributed throughout the stroma and localized to a ring-like structure at the chloroplast division site. We demonstrate that ARC6 recruits ARC3 to the division site to form a ring-like structure, likely through direct interaction. This ARC6–ARC3 interaction enables ARC3 to bind FtsZs. Furthermore, we show that the ARC6–ARC3 complex significantly promotes the dynamics of chloroplast Z rings reconstituted in a heterologous system. Finally, the constriction of these reconstituted Z rings is markedly enhanced by ARC6–ARC3. Our findings reveal a regulatory mechanism that governs Z-ring dynamics and constriction, shedding light on the molecular mechanisms underlying chloroplast division.

The commercial value of cucumbers is influenced by the presence of spines or trichomes on their fruit, while the trichomes found on other parts of the plant are essential for protecting the cucumber against a range of biotic and abiotic stresses. In our research, we identified a glabrous nwd mutant from EMS-induced cucumber (Cucumis sativus L.) mutant lines. This mutant displays a consistent glabrous phenotype across all plant organs. Upon analysis, it was revealed that the nwd mutation is governed by a lone recessive nuclear gene. The nwd plants show a significant reduction in both their photosynthetic capacity and chlorophyll a content when compared to the wild-type. Furthermore, there are notable changes in the antioxidant enzyme activities, soluble protein levels, and malondialdehyde content of the nwd mutant. Genotyping and MutMap approaches identified the CsNWD gene, encoding a VPS protein, as a candidate responsible for the glabrous trait. Transcriptome analysis indicated that 15 trichome-related genes exhibit significant expression changes in the nwd mutant, implying that CsNWD may regulate trichome development through interactions with these genes. This study contributes to the understanding of VPS proteins in trichome initiation and the underlying mechanisms of trichome development.

Plant Unconventional Prefoldin RPB5 Interactor (URI) proteins are key functional factors regulating plant growth, development, and stress responses, playing important roles in root morphogenesis, gravitropism regulation, and environmental stress signaling pathways. To investigate the biological function of the pepper URI gene, we identified the pepper URI homolog (CaURI) through sequence alignment and performed functional characterization using multiple molecular approaches. The pepper URI gene successfully rescued the shortened root length and impaired the root gravitropism phenotypes of the Arabidopsis uri-1 mutant. Subcellular localization revealed that the pepper URI protein was localized in the cytoplasm. Overexpression of pepper URI in Arabidopsis significantly inhibited root and hypocotyl elongation. RNA-seq analysis revealed that the expression patterns of many genes involved in growth and development were significantly altered in the CaURI-overexpressing Arabidopsis. Silencing of the endogenous pepper URI gene led to a marked reduction in plant height, and this dwarf phenotype was further aggravated under heat stress conditions. This work enriches the functional framework of the plant URI gene family and provides valuable genetic resources and a theoretical basis for dissecting the molecular mechanisms underlying pepper growth regulation and heat tolerance.