Genome-wide identification and analysis of the cysteine-rich transmembrane module genes in Chinese cabbage (Brassica rapa L. ssp. Pekinensis) and BrCYSTM1 is involved in leaf size development.

BACKGROUND: Cysteine-rich transmembrane module (CYSTM) peptides are ubiquitous in eukaryotes and primarily involved in stress responses and defense mechanisms. To date, no comprehensive genomic identification of this family in Chinese cabbage has been reported, and the biological functions of the CYSTM genes in Chinese cabbage remain largely unexplored. RESULTS: Nine members of the CYSTM family were identified in Chinese cabbage and was named according to their homologous genes in Arabidopsis. DNA structure and motif analyses revealed that the CYSTM family is highly conserved. Evolutionary analysis suggests that Chinese cabbage shares a more closely related lineage with other Brassicaceae species in comparison to Arabidopsis. Expression pattern analysis demonstrated that the BrCYSTM genes exhibit considerable variation across different tissues and display diverse expression patterns in response to various hormone treatments and abiotic stresses. Since leaf traits are directly associated with the yield of Chinese cabbage, and BrCYSTM1 exhibits the highest expression level in Chinese cabbage leaves, we conducted an array of in-depth studies on this gene. BrCYSTM1 undergoes self-association to form homodimer and also interacts with BrCYSTM10a or BrCYSTM10b to establish heterodimers. The Bimolecular Fluorescence Complementation (BiFC) assay demonstrated that these dimers are localized both in the cytoplasm and on the plasma membrane, suggesting their potential involvement in signal transduction processes. The overexpression of BrCYSTM1 in both Chinese cabbage and Arabidopsis significantly enlarged leaf size, with a similar effect observed in the AtCYSTM1 mutant background. These findings support the role of BrCYSTM1 in promoting leaf growth, indicating its potential involvement in regulating leaf size. CONCLUSIONS: Our results suggest that BrCYSTMs are involved in the response of plants to a variety of stresses. The role of BrCYSTM1 as a positive regulator of leaf development is well established in Arabidopsis, and its conserved function gains preliminary support from overexpression studies in Chinese cabbage.