| Maize is the third most important crops in the world, and its cultivated acreage is just behind wheat and rice. The cultivated area of maize is widespread in our country, and Maize is one of the main grains for people in northern China, southwest mountains and other dry gulch area. Lack of soil phosphorus is one of significant reasons limiting Maize yield potential. Selection and breeding of maize varieties with highly effective absorbtion and utilization of phosphorus using molecular biology technology can solve the problem of lack of soil phosphorus efficiently. In order to understand stress response mechanisms of phosphorus starvation in maize, this study analyzes the gene differential expressions in maize under the condition of phosphorus starvation at the level of transcriptome using cDNA-SRAP. The main results are as follows:1. The best reaction system and PCR program of cDNA-SRAP were established to adapt to differential expression analysis of low phosphorus tolerance gene in maize. Hydroponic cultivation were carried out to cultivate Maize inbred line 478, these seedlings were respectively cultivated 0,3,5 and 7days by low phosphorus supply and isolated total RNA, then leaves and roots cDNA were obtained by RT-PCR from total RNA, these cDNA were named L0, L3, L5, L7, R0, R3, R5 and R7. We obtained the best cDNA-SRAP reaction system and PCR program using these cDNA as amplification templates. The best reaction mixture contained cDNA template 140ng, dNTP mixture 0.25mmol/L, Mg2+ concentration 1.8mmol/L, forward and reverse primers concentration 0.5μmol/L respectively, and Taq DNA polymerase 1.0 U. The protocol was initially denaturing at 94℃for 5 min; 94℃30 s,35℃30 s,72℃1 min for the first five cycles, then the annealing temperature was raised to 50℃for another 35 cycles. Finally, a terminal extension step at 72℃for 10 min. 2. A large number of differential expression fragments related to the stress of phosphorus starvation were obtained. PCR reactions were carried out with cDNA leaf and root of 478 with phosphorus starvation treatment 0 day,3 days,5 days and 7days, and 30 pairs of SRAP primers. The PCR products were detected by using urea-polyacrylamide gel electrophoresis. We selected and eluted 378 gene differential expression fragments.210 fragments were obtained from leaves and 168 fragments were obtained from roots. Inhibition, induction, upgraduation, downgraduation and feedback regulation fragments have 83,240,4,11 and 40 respectively, account for 22.0%,63.5%,1.1%,2.9% and 10.6%, respectively.3. Sequence informations of some fragments were obtained by NCBI Blast, and then we predicted the functions of these fragments. The recovered fragments of gene differential expression were amplified in the second PCR, then 41 positive clones were selected and 20 positive clones were sequenced. Through sequence alignment Blast-X in NCBI, we find out the homology protein of 11 fragments, and then predicted the function of these gene fragments.
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