Genome-Wide Identification of Genes and Functional Analysis of Involved in Ca Transport and Ca Deficiency-Induced Tip-Burn in Chinese Cabbage ( L. ssp. ).

Calcium (Ca) plays essential roles in plant growth and development. Ca deficiency causes a physiological disorder of tip-burn in Brassiceae crops and is involved in the regulation of cellular Ca homeostasis. Although the functions of Ca/H exchanger antiporters (CAXs) in mediating transmembrane transport of Ca have been extensively characterized in multiple plant species, the potential roles of genes remain unclear in Chinese cabbage. In this study, eight genes of the family were genome-widely identified in Chinese cabbage. These BrCAX proteins contained conserved Na_Ca_ex domain and belonged to five members of the family. Molecular evolutionary analysis and sequence alignment revealed the evolutionary conservation of family genes. Expression profiling demonstrated that eight genes exhibited differential expression in different tissues and under heat stress. Furthermore, Ca deficiency treatment induced the typical symptoms of tip-burn in Chinese cabbage seedlings and a significant decrease in total Ca content in both roots and leaves. The expression changes in genes were related to the response to Ca deficiency-induced tip-burn of Chinese cabbage. Specially, and genes were highly expressed gene members of the family in the leaves and were significantly differentially expressed under Ca deficiency stress. Moreover, overexpression of and genes in yeast and Chinese cabbage cotyledons exhibited a higher Ca tolerance, indicating the Ca transport capacity of and . In addition, suppression expression of and genes reduced cytosolic Ca levels in the root tips of Chinese cabbage. These results provide references for functional studies of genes and to investigate the regulatory mechanisms underlying Ca deficiency disorder in Brassiceae vegetables.