The Evaluation Of Drought Resistance And The Study On Drought Resistant Mechanism Of Two Ephemeral Plants

Xinjiang is a big agricultural province, but the crops often suffer from the special desert environment. Cultivating drought resistant varieties has become one of the key ways to solve this problem.Conventional drought resistant breeding just uses a hybrid approach between similar species for to get better drought resistant varieties, which is longer period and lower the efficiency of screening, it has been greatly restricted the using of drought resistant genes. Cultivating drought resistant varieties through genetic engineering can greatly shorten the breeding cycle, take full advantage of the drought resistant resources, and greatly increase the efficiency of agricultural breeding, so it has greater potential in plant drought resistant breeding. However, the key to do the genetic engineering breeding is hunting the genes with obvious function.In this study, with the Sisybrium altissimum and Conringia planisiliqua as materials, we analyzed their drought resistance through a number of indices in order to reveal their drought resistant mechanism. Then, we found the functional genes, which was obvious effection and closely related with drought resistance. Finally, we cloned the related genes. The results showed that:1. Maximum tolerance of PEG concentration of Sisybrium altissimum and Conringia planisiliqua is15%to20%during seed germination. In the seedling period, the lethal concentration of Sisybrium altissimum and Conringia planisiliqua reached more than30%.2. Sisybrium altissimum and Conringia planisiliqua were treated with drought stress by25%PEG. And then we determined some physiological and biochemical indices such as proline, betaine, MDA, SOD, POD, CAT. The results showed that:these indicators had significant changes after drought stress, which responsed to drought stress. Comprehensive analysis indicated that the drought resistance of Conringia planisiliqua should be stronger than Sisybrium altissimum.3. We monitored the expression of P5CS. POD and HRD in Sisybrium altissimum and Conringia planisiliqua by real time quantitative RT-PCR, and determined proline content and POD activity at the corresponding stress time. The results showed that:compared to the controls, the levels of P5CS,POD and HRD were obviously up-regulated after drought stress, at the same time, the content of proline and the activity of POD were increased or decreased（feedback inhibition） in them. HRD genes showed varying degrees of up-regulating in Sisybrium altissimum and Conringia planisiliqua, and the expression of HRD of Sisybrium altissimum reached the maximum after the stress8h, but for the HRD of Conringia planisiliqua was24h.4. According to HRD transcription factor （NM₁29202.1） of Arabidopsis thaliana, which was published in NCBI, We designed primers, and cloned the HRD genes from Sisybrium altissimum and Conringia planisiliqua with the method of PCR, and then named SaHRD and CpHRD respectively. The length of HRD genes of Sisybrium altissimum and Conringia planisiliqua was549bp, and it can encode182amino acids. Using BLAST alignment in NCBI, the homology of SaHRD and CpHRD was87%and86%and the amino acid sequence can reach79%compared with HRD of Arabidopsis thaliana; the homology of SaHRD and CpHRD was79%compared with HRD of Arabidopsis lyrata, for the the amino acid sequence was80%and81%. We also found that the amino acid sequence of HRD including highly conservatively AP2/ERF structure domain.