| Drought is one of main factors having an influencing on the production of corn (Zea mays L.). Screening a batch of maize varieties, which have a strong drought resistant characteristics, and giving a further research on its drought resistant mechanism is a good work, which means a lot towards the cultivation and breeding of the drought resistant varieties of corn. Considering this, first of all, with the use of fuzzy membership function method, this research gives an evaluation to 30 maize hybrids, which is promoted to be planted in southwest region, on its drought resistant characteristics. Secondly, this research will give a further research to the drought resistant physiology and the corresponding molecule mechanism of 2 hybrids and 2 inbred lines, which is proved to have a significant difference in their drought resistant, through the methods of determining traditional physiological indexes, digital gene expression profiling (DGE), protein quantification (iTRAQ), etc. The main results are as follows:1. Based on the use of comprehensive drought index, screening 8 maize hybrids equipped with strong drought resistant characteristics.2. Based on the use of index of the variation for drought, as they are sensitive to drought stress, they, which include leaf area, root shoot ratio, root traits (root volume, root branch number, root length), relative electrolytic leakage, rates of water loss, proline, chlorophyll and chlorophyll fluorescence parameters (the maximum photochemical efficiency, the actual photochemical efficiency, the original light energy capture efficiency, photochemical quenching coefficient) can be used as evaluation indexes for the drought resistant characteristics of corn in seeding stage.3. Under different intensity of drought stress, the resistant varieties’seedling height and leaf area experience a downtrend. However, their descend range is smaller than the sensitive varieties. What’s more, the root shoot ratio experience an uptrend in a total, and its ascensional range is higher than the sensitive varieties. The accumulation amount of dry matter accumulation will experience no obviously change after light or moderate drought stress, but a decrease after severe drought stress. The accumulation amount of dry matter accumulation in sensitive varieties will experience an obviously downtrend after drought stress.4. Under different intensity of drought stress, the maize varieties’ chlorophyll, the maximum photochemical efficiency, the original light energy capture efficiency, FPSII, net photosynthetic rate, transpiration rate will experience a downtrend, but its non-photochemical quenching coefficient will experience an uptrend. The change ranges of resistant varieties’ all characters are smaller than those of sensitive varieties.5. Under different intensity of drought stress, the cell membrane stability of resistant varieties will experience a downtrend, and its change range is smaller than that of sensitive varieties. Proline and SOD content will experience an uptrend, and its change range is higher than that of sensitive varieties. Rates of water loss will experience an uptrend, and its change range is higher than that of sensitive varieties.6. Through the DGE sequencing work, we got over 4 million clean tags. Tags, whose copy number is more than 100, have the most amount. Tags, whose copy number is less than 5, have the most kinds.7. Through analyses on the natural antisense transcription product, we have a discovery that about 50% genes of maize inbred lines have sense-antisense regulation way. The drought stress lower 2 maize inbred lines’ total amount of gene producing antisense transcripts.8. Through DEG method, we screen out the differential genes of 2 maize inbred lines under different intensity of drought stress. We did some comparison with the use of Venn diagram, and also held some analyses to the function and metabolic pathways of intervarietal differential genes set. The results can be concluded as follows:1. Resistant varieties have the ability of continually eliminate free radicals under long term drought stress.2. Under short term drought stress, resistant varieties are different form sensitive varieties. First, difference of enrichment phenomenon is existed towards the antioxidant activity, which is the one kind molecular function of their differential genes. Second, difference of enrichment phenomenon is existed towards response to stimulus, which is happened in the biological process.9. Through some comparison with the use of Venn diagram, we distinguish drought resistant related genes and fertility related genes in 2 inbred lines with different drought resistance during the 1-24h of drought stress for the first time. By doing some corresponding analyses work, we found that one of molecular mechanism for the drought varieties suitable for the drought environment is compounding secondary metabolite in a large number, and in time.10. With the use of iTRAQ method, we got 2466 proteins through this identification work. We identified 6 differentially express proteins in signal transduction under drought stress. Through the analyses towards differential proteins, we found that the partial overlapping is existed to each transmission route of corn drought stress response and cytokinin signal. What’s more, under drought environment, the different expression pattern of phytohormone’s related genes may be one of reasons leading to the drought resistance difference among different genotype maize.11. Did a correlation analysis towards mRNA and protein, we got about 1300 genes which can be expressed in two levels.In conclusion, this research screened out a batch of corn varieties equipped with a strong drought resistant characteristic so that it is valuable to apply them for actual production. Meanwhile, this research did the further research to the screening varieties’ drought resistant physiology and the corresponding molecule mechanism, which also provide theoretical basis for the establishment of the identification system for maize drought resistance. |
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