Leaf color is one of the most important agronomic traits of Chinese cabbage ( Brassica rapa L. ssp . Pekinensis ). However, the molecular mechanism underlying leaf color development in Chinese cabbage remains largely unexplored. In this study, a juvenile leaves yellowing ( jly ) mutant was screened from an EMS-mutagenized mutant library of Chinese cabbage A03. The jly mutant displayed reduced chlorophyll and starch content, impaired photosynthetic efficiency, accumulated reactive oxygen species (ROS) in yellowed juvenile leaves, and abnormal chloroplast development. Using MutMap and KASP technologies, the gene BrRNE was identified as regulating the juvenile leaves yellowing phenotype in Chinese cabbage. BrRNE was preferentially expressed in leaves, and BrRNE was localized in chloroplasts. VIGS validation confirmed a significant association between the BrRNE gene and the leaves yellowing phenotype. Mutation of the BrRNE induced alternative splicing variants. Western blot analysis demonstrated that the BrRNE mutation impaired the expression of photosynthesis-related proteins in the jly mutant. Transcriptome analysis revealed significant activation of the retrograde signaling in the jly mutant, accompanied by marked upregulation of the chloroplast quality control system. Expression of genes involved in chlorophyll metabolism, sugar metabolism, and photosynthesis-related pathways was suppressed. Additionally, miRNAs involved in regulating the expression of genes in the chlorophyll metabolism and sugar metabolism pathways within the forward signal pathway were identified, including bra-miR824-p3, mtr-miR171b, bra-miR390-3p, and ath-miR158a-3p. This study identifies the gene BrRNE as a regulator of the juvenile leaves yellowing phenotype and constructs a comprehensive miRNA-mRNA co-regulation network for plant leaf color development, viewing the process of leaves color development from the perspective of intracellular signaling exchange.
Li et al. (Fri,) studied this question.