论文部分内容阅读
Violaxanthin de-epoxidase (VDE),a key enzyme of xanthophyll cycle,catalyzes conversion from violaxanthin (V) to zeaxanthin (Z) through antheraxanthin (A) to protect photosynthesis apparatus.A cDNA,PeVDE,encoding a VDE was isolated from bamboo (Phyllostachys edulis) by RT-PCR and RACE methods.PeVDE is 1,723 bp and contains an ORF encoding 451 amino acids,with a transit peptide of 103 amino acids.The mature protein is deduced to have 348 amino acids with a calculated molecular weight of 39.6 kDa and a theoretic isoelectric point of 4.5.Semi-quantitative RT-PCR assay indicated that the highest expression level of PeVDE was in leaf,which agreed with the accumulation pattern of PeVDE protein.Real time PCR results showed that PeVDE was up-regulated and reached the highest level after the treatment (1200 μmo1·m-2·s-1) for 2 h,then decreased and kept at the level similar to that of 0.5 h after treatment for 8 h.To investigate the function of PeVDE,mature protein was heterologously expressed in Escherichia coli and the enzymatic activity assay was carried out using V as substrate.The pigments that formed in the reaction mixture were extracted and analyzed by HPLC method.Besides V,A and Z were detected in the reaction mixture,which indicated that the recombinant protein exhibited enzymatic activity of catalyzing V into Z through A.This study indicates that PeVDE functions through regulating the components of xanthophyll cycle,which might be one of the critical factors that contribute to the growth of bamboo under naturally varying light conditions.