| The xanthophylls cycle refers to the conversion among zeaxanthin, antheraxanthin and violaxanthin, which plays a significant role in plant photoprotection process. In this paper our aim is to investigate the change induced by leaf senescence on the level of gene expression, protein and pigments involved in xanthophylls cycle.Methods:We selected Chinese spring CS and stay-green Chuannong 12 leaves, and carried out the following work: (1) According to the conserved sequence, we designed specific primers for zep gene, performed RT-PCR experiment, and subsequently cloned the gene and sequenced. (2) The leaves were collected from CS and Chuannong12 at various times during senescence, and the content of Chla, Chlb, soluble protein and malondialdehyde (MDA) were measured. Simultaneously, Native-PAGE was done to provide us the information concerning photosynthetic protein. The relative contents of carotenoid molecules were analyzed by using High-Performance Liquid Chromatograph. (3) The changes on mRNA stable level of lycopene epsilon-cyclase (lec), lycopene beta-cyclase (lbc) and beta-carotene hydroxylase (bch) were studied by semi-quantitative PCR experiments.Results: (1) The partial sequence of zep gene was obtained, and data analysis revealed that wheat zep gene has higher sequence homology with rice zep gene. (2) During the senescence procedure, the contents of Chla, chlb and soluble protein were gradually decreased, in contrast, MDA had higher content as the time prolonged. Native-PAGE analysis showed that the PSI reaction center or LHCII trimer experienced the decrease of content. (3) HPLC results indicated that leaf senescence gave rise to the higher relative content of violaxanthin and zeaxanthin, however, lowerβ-carotene was detected. (4) RT-PCR results suggested that mRNA level of lbc gene was up-regulated by senescence signal. . |
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