Functional Analysis Of Maize Protein Kinase Genes ZMPTI1, ZMPTI1-1and ZMCIPK2in Drought Resistance

Maize is one of the most important crops in the world. With the global water shortage, drought stress has been a major constraint for maize production. It is of vital theoretical and practical significance for maize genetic breeding in drought resistance to analyze gene function in drought resistance, discover new drought resistance genes and cultivate new drought resistance maize lines. Protein kinase plays an important role in plant drought resistance process. In this research, transgenic ZmPtil, ZmPtil-1and ZmCIPK2, which induced by drought stress from maize, overexpressed or RNAi lines of Jing178or Jing501inbred maize were constructed via pollen tube pathway method or microprojectile bombardment. The function in drought resistance of these transgenic lines was further analyzed. The results showed as follows:In order to analyze the drought resistance function of ZmPtil, the plant expression vector pBPC-ZmPtil-bar was constructed and transformed into maize via pollen tube pathway method. The different drought resistance index of transgenic ZmPtil maize plants was analyzed. The results showed that the transgenic plants can enhance the drought resistance comparing to control plants. Under drought stress, compared to wild-type plants, transgenic ZmPtil plants showed a stronger growth recovery phenotype with less leaf rolling and better growth with higher plant height and dry weight, which was6.2%and12.6%higher than WT, respectively. The grain number per ear and1000-grain weight of transgenic plants was21.9%and8.7%higher than WT, respectively. After drought stress, the relative electric conductivity and MDA content of transgenic plants was14.8%,18.1%lower than that that of WT, respectively, whereas the relative water content, total soluble sugars, proline content of transgenic plants was7.3%,2.5%,22.7%higher than that that of WT, respectively.In order to analyze the drought resistance function of ZmPtil-1, the plant expression vector35S-ZwPri1-1-DHA-NOS-pGreen0029was constructed and transformed into Arabidopsis via floral dip method. The different drought resistance index of transgenic ZmPtil-1Arabidopsis plants was analyzed. The results demonstrated that over-expression of ZmPtil-1gene improved drought resistance in transgenic Arabidopsis. Under drought stress, compared to wild type, survival rate of the three transgenic lines, which was70%,76%and87%respectively, was significantly higher than that of wild type which was29%. Under drought stress, compared to wild-type plants, transgenic ZmPtil-1Arabidopsis plants showed a stronger growth recovery phenotype with less wither leaves and better growth. The seed weight of transgenic plants was58.7%higher than WT. After drought stress, the relative electric conductivity and MDA content of transgenic plants was13.7%,17.7%lower than that that of WT, respectively, whereas the relative water content, total soluble sugars, proline content of transgenic plants was7.1%,3.6%,22.5%higher than that that of WT, respectively.In order to further analyze the effect of ZmPtil-1on the drought tolerance of maize, the plant expression vector pGreenO229-ZmPtil-1was constructed and transformed into maize via microprojectile bombardment method. The different drought resistance index of transgenic ZmPtil-1maize plants was analyzed. The results demonstrated that over-expression of ZmPtil-1gene improved drought resistance in transgenic maize. Under drought stress, compared to wild-type plants, transgenic ZmPtil-1plants showed a stronger growth recovery phenotype with less leaf rolling and better growth with higher plant height and dry weight, which was8.2%and14.4%higher than WT, respectively. The grain number per ear and1000-grain weight of transgenic plants was22.2%and8.8%higher than WT, respectively. After drought stress, the relative electric conductivity and MDA content of transgenic plants was20.4%,24.1%lower than that that of WT, respectively, whereas the relative water content, total soluble sugars, proline content of transgenic plants was9.4%,9.0%,24.1%higher than that that of WT, respectively.A family of specific protein kinase CIPK participates in regulation of osmotic stress, salt, cold, ABA and sugar signal transduction in plant. ZmCIPK2(GenBank accession no. EF158033) is a new maize CIPK kinase gene. Transgenic ZmCIPK2Arabidopsis lines are hypersensitive to drought stress when germination and early seedling growth. In order to analyze the drought resistance function of ZmCIPK2, the RNAi expression vector pGreenO229-ZmCIPK2Sense-GFP-ZmCIPK2Antisense was constructed and transformed into maize via pollen tube pathway method. The expression level of ZmCIPK2in RNAi maize lines was declined to some extent and even completely silenced. The results showed that the RNAi lines can enhance the drought resistance comparing to control plants. Under drought stress, compared to wild-type plants, ZmClPK2RNAi plants showed a stronger growth recovery phenotype with less leaf rolling and better growth. After drought stress, the relative electric conductivity and MDA content of transgenic plants was16.1%,17.5%lower than that that of WT, respectively, whereas the relative water content, total soluble sugars, proline content of transgenic plants was8.2%,8.8%,24.2%higher than that that of WT, respectively.