Ethephon-Induced Senescence And The Relevant Genes Differential Expression Analysis Of Brown Cotton Cotyledon

Leaf senescence not only affects the yields of cotton, but also decreases the quality of cotton fiber. Therefore, the study of the cotton leaf senescence has an important theoretical and practical significance. As a growth regulator, ethylene participates in multiple development procedures of plant, such as seedling, flowering, fruiting, tissue aging and response to environmental stress. At present, there are few reports about ethylene roles in the cotyledon senescence of brown cotton. In this study, POD, SOD, CAT activities and MDA content of the brown cotton cotyledon with ethephon treatment were measured to esearch the influence of ethephon on cotyledon senescence. In addition to. the cDNA-SRAP experiment was performed to isolate the genes involved in brown cotton cotyledon senescence. The results of this study will facilitate the understanding of molecular mechanisms about brown cotton cotyledon senescence. The main findings are as fellows:(1) Morphological observation of brown cotton cotyledons with ethephon treatment showed that it was no significant changes in the brown cotton cotyledon color when ethephon concentration was lower than250mg.L-1, but cotyledon color turned yellow and accelerated aging when ethephon concentration was higher than250mg.L-1.(2) The results displayed the higher ethephon concentration, the higher contents of chlorophyll and carotene when the ethephon concentration was less than150mg.L-1. The contents of chlorophyll and carotene of brown cotton cotyledon decreased when the ethephon concentration was higher than250mg.L(3) The results showed that the activities change trends of POD. SOD. CAT were almost same when ethephon concentration was between0and1000mg.L-1. They all had higher activities when cotyledon was treated with low concentration of ethephon. and all had lower activities cotyledon when cotyledon was treated with high concentrations of ethephon. Particularly CAT, POD activities increased significantly at the concentration of ethephon from0to 50mg.L-1,but their activities decreased rapidly when ethephon concentration exceeded50mg.L-1. The SOD activity reached the maximum value when ethephon concentration was150mg.L-1, but its activity decreased significantly when ethephon concentration was more than150mg.L-1. With activity changes of the three protective enzymes, the content of MDA also changed negatively at the same time.(4)150,500mg.L-1ethephon induced brown cotton cotyledons, the three protective enzymes are realizable for a short period of time increased, then decreased. After24h, the treaterment group of500mg.L-1SOD activity was lower than the control group, but MDA content was significantly higher than that. That the membrane lipid of serious, exacerbated by aging.(5)873cDNA fragments were obtained by cDNA-SRAP technology with60-pair-primer combinations. Among of them, there were101cDNA differential fragments. At last,32differential fragments with excellent reproducibility were cloned and sequenced. The results of Bioinfomatic analysis showed that the32differential fragments could be classified into9functional families. They were all related to the aging and shedding of plant organs.