Effects of 1-MCP and ethylene on expression of three CAD genes and lignification in stems of harvested Tsai Tai (Brassica chinensis)

Tsai Tai (Brassica chinensis) is produced mainly in China but also consumed overseas. The stems of Tsai Tai are subject to toughening due to lignification. Cinnamyl alcohol dehydrogenase (CAD) is a key enzyme involved in lignin biosynthesis. Three full-length CAD cDNAs were isolated, encoding proteins of 288, 323, and 323 amino acids, respectively. Sequence analysis showed that they share a highly conserved putative NAD/NADP(H)-binding site at the amino terminus. All the three BcCAD genes responded to 1-MCP and ethylene within 2 h. Ethylene up-regulated expression of BcCAD1-1 and BcCAD2, while 1-MCP down-regulated them. Ethylene increased yellow leaves and stem lignin, and 1-MCP decreased them. These results suggest ethylene is involved in lignin growth in Tsai Tai, and induced expression of BcCAD1-1 and BcCAD2 could contribute to lignification. They also suggest removal of ethylene and application of 1-MCP could extend shelf-life and knockout of certain CAD genes could produce lines that store well.