Identification of genes related to tipburn resistance in Chinese cabbage and preliminary exploration of its molecular mechanism

BACKGROUND Tipburn, also known as leaf tip necrosis, is a severe issue in Chinese cabbage production. One known cause is that plants are unable to provide adequate Ca2+ to rapidly expanding leaves. Bacterial infection is also a contributing factor. Different cultivars have varying degrees of tolerance to tipburn. Two inbred lines of Chinese cabbage were employed as resources in this research. RESULTS We determined that the inbred line 'J39290' was the tipburn resistant material and the inbred line 'J95822' was the tipburn sensitive material based on the severity of tipburn, and the integrity of cell membrane structure. Ca2+ concentration measurements revealed no significant difference in Ca2+ concentration between the two materials inner leaves. Transcriptome sequencing technology was also used to find the differentially expressed genes (DEGs) of 'J95822' and 'J39290', and there was no significant difference in the previously reported Ca2+ uptake and transport related genes in the two materials. However, it is evident through DEG screening and classification that 23 genes are highly linked to plant-pathogen interactions, and they encode three different types of proteins: CaM/CML, Rboh, and CDPK. These 23 genes mainly function through Ca2+-CaM/CML-CDPK signal pathway based on KEGG pathway analysis, protein interaction prediction, and quantitative real-time PCR (qRT-PCR) of key genes. CONCLUSIONS By analyzing the Ca2+ concentration in the above two materials, the transcription of previously reported genes related to Ca2+ uptake and transport, the functional annotation and KEGG pathway of DEGs, it was found that Ca2+ deficiency was not the main cause of tipburn in 'J95822', but was probably caused by bacterial infection. This study lays a theoretical foundation for exploring the molecular mechanism of resistance to tipburn in Chinese cabbage, and has important guiding significance for genetics and breeding.