Comparative Analysis Of Carotenoid Biosynthetic Enzyme Gene Expression In Juhongxin And Popular Heading Chinese Cabbage

The heading Chinese cabbage is an important vegetable crop in China. Its leafy head is the main eaten part that has rich nutrients. The "Beijing Juhongxin" heading Chinese cabbage is bred by the Vegetables Research Center of Beijing Academy of Agriculture and Forestry Sciences. Its orange and red leafy head has several times more of carotenoids than popular heading Chinese cabbage. In order to understand the mechanism controlling the carotenoid biosynthesis of "Beijing Juhongxin", we comparably analyzed nine carotenoid biosynthetic enzyme gene expression during the heading stage between the "Beijing Juhongxin" and popular heading Chinese cabbage. From the published gene sequences encoding the 9 enzymes involved in carotenoid biosynthesis of plants, we designed 80 pairs of degenerated primers and 9 were chosen in gene expression analysis by RT-PCR. Through RT-PCR and Southern blotting, we confirmed that the two kinds of heading Chinese cabbage both have the nine genes, and they are all expressed in the heading stage. Furthermore, main components of carotenoid biosynthetic pathways were analyzed by HPLC in both materials. The results showed that "Beijing Juhongxin" contained a great deal of lycopene while it was not detected in popular heading Chinese cabbage, and neither of them had detectable a-carotene. The total carotenoid content of "Beijing Juhongxin" was seven times of that of popular Chinese cabbage.From our preliminary results and previous data, we concluded that the mRNA levels of GGPS, PSY, PDSand ZDS in "Beijing Juhongxin" are higher than those of the popular one at the heading stage, while the expression levels of p -LYS and e-LYS in "Beijing Juhongxin" are possible to be equal to or less than those of the popular Chinese cabbage. It needs further study to see if there is difference between the VDE and ZEP gene expression levels. With our work going on, we will determine the mRNA levels of these nine genes, and clone these genes for heading Chinese cabbage. This work will be valuable for-2-understanding the molecular mechanism of gene regulation in carotenoid biosynthesis and can be served as the basis for the metabolic engineering of heading Chinese cabbage and other related crops.