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Studies on Seed Dormancy of the Main Maize Inbred Line 08-641 in Southwest China

Author: LengYiFeng
Tutor: RongTingZhao;LanHai
School: Sichuan Agricultural University
Course: Biochemistry and Molecular Biology
Keywords: maize seed dormancy storage substances endogenous hormones two dimensional electrophoresis proteome
CLC: S513
Type: Master's thesis
Year: 2011
Downloads: 50
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Abstract


Maize(Zea mays L.), the often cross-pollinated plant of gramineae, is one of the three crops in the world’s agricultural production, and its planting area and gross product are only second to rice in china. Because the special natural climate of overabundant rain and poor sunshine in the southwest, pre-harvest sprouting has seriously affected the quality and yield of maize, looking for a good material with resistance to pre-harvest sprouting is the urgent need for improvement of existing maize strains. Therefore, the germinating capacity of 28 maize inbred lines with different degrees of seed dormancy was first measured and compared in this study, and the effects of soluble sugar, starch, soluble protein and endogenous hormones ZT, GA3, IAA, ABA contents andα-amylase activity on seed dormancy and germination in fresh seeds of 7 maize inbred lines have been studied; As far as the reason of seed dormancy is concerned, the embryo structure of the strongest dormancy inbred line R08 seed was observed, and the changes of protein expression during afterripening of R08 seed were compared using proteomics method.The main results of this study are as follows:1. The results of identification for seed dormancy of different maize inbred lines show that fresh seeds of different maize inbred lines have different degrees of seed dormancy. The seed germination rate of 28 maize inbred lines ranging from 0 to 100%. According to the seed germinating capacity,28 maize inbred lines are divided into five groups:3 extremely high dormancy inbred lines,6 relatively high dormancy inbred lines,1 moderate dormancy maize inbred lines,9 weaker dormancy maize inbred lines, and 9 maize inbred lines with normal germination.2. Dormant seeds of maize inbred line R08 have a complete embryo structure that contains embryo, hypocotyl, radicle, cotyledon, the seed dormancy of R08 is not caused by incomplete embryo structure.3. The contents of soluble sugar, soluble protein, and starch andα-amylase activity in seeds of different maize inbred lines were comparative analysed. The results show that theα-amylase activity in R08 seeds is higher than non-dormant seeds, this may becauseα-amylase in dormant seeds plays a role in seed dormancy later than in normal seeds; andsoluble protein and soluble sugar contents of maize inbred lines with normal germination are higher than the dormant inbred lines, in which inbred line 9LY05028 is the most prominent; while the starch content in dormant seeds of R08 is higher than other inbred lines. For such results, we believe that the preparation for the metabolism of related substances has already completed for the strong metabolic activity in seeds with normal germination before harvest, while the similar physiological activities have not yet begun or are about to carry out in dormant seeds.4. The comparative analysis of Endogenous hormones ZT, GA3, IAA, ABA levels in seeds of different maize inbred lines indicate that the ZT and GA3 contents in maize inbred line R08 were significantly lower than other inbred lines, according to previous research findings related to the two hormones, we speculate that the physiological activities egulated by ZT and GA3 can not process without their participation, thus preventing the normal metabolism for germination in seed; the IAA and ABA contents in the seeds of non-dormancy inbred line 9LY05028 is higher than other inbred lines; We also found that the ABA and ZT levels are very high in seeds of inbred lines 9LY05028 and A318, but the two lines have weak seed dormancy even no dormancy, in which the cytokinin may play a " disinhibition effect " role to the dormant seeds caused by ABA, making the presence of ABA can not prevent the normal germination of seeds.5. Proteome of R08 seeds has significantly changed during afterripening. There are 23 different expression proteins in the seeds of maize inbred line R08 with 10d afterripening process when the samples were analysed through 2-DE, in which there are 8 new induced expression proteins,7 missing expression proteins,4 up-regulated expression proteins,4 down-regulated expression proteins; 9 different expression proteins were obtained in R08 seeds with 15d afterripening process, in which 1 new expression protein was induced,2 missing expression proteins,5 up-regulated expression proteins,1 down-regulated expression protein. Among the 18 proteins identified by mass spectrometry, there are 6 storage proteins,3 proteins involved in metabolism,2 proteins involved in regulating protein structure and cell function,1 protein involved in photosynthesis,6 proteins with unknown function. The changes of protein expression during seeds ripening with dry process indicate that the seeds have completed a series of physiological and biochemicalactivities befor they can germinate normally, and deeply study on the biological function of these proteins will help us understand maize seed dormancy more clearly.As stated previously, The results of our study show that the seed dormancy of R08 is extremely strong, metabolism related to seed dormancy processing later than non-dormant seeds, and GA3 content is significantly lower than the seeds with normal germination, in addition, the expression level of specific protein also limit the normal germination of R08 seeds. The purpose of this study is to identify the seed dormancy of R08 and to lay a foundation for the study of seed dormancy mechanism in a deep-going way.

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