The Cold Shock Protein Gene CSP From Marine Microorganism Improves Drought And Cold Tolerance Of The Transgenic Maize

Maize(Zea mays L.)is an important food crop and feed source in China.Drought andlow temperature seriously affect the yield and quality of maize.In recent years,breeding new maize varieties with resistance to stress through genetic engineering technology has become the research trend of breeding.Cold shock proteins(CSPs)are a class of highly conserved nucleic acid binding proteins that are widely present in bacteria,plants and animals,it can be used as a RNA chaperone to participates in cell physiological activities such as growth and abiotic stress response,and to enhances the ability of cells to resist external stress.At present,there are some reports on the expression of the cold shock protein gene to improve plant stress resistance,but the gene source is limited to only a few known microorganisms or plants.99%of marine microorganisms are not culturable,in our previous work,a cold shock protein gene(CSP)was cloned from the macrogenome of marine microorganism,which was constructed into the plant expression vector and transferred into Arabidopsis.The results of physiological detection showed that the introduction of CSP gene improved the drought resistance and cold resistance of Arabidopsis.In this study,the recombinant plasmid Ubi::CSP was transformed into maize by Agrobacterium-mediated immature embryo infection,and nine positive transformation events were obtained through cocultivation,recovery,screening,differentiation and regeneration.T0 transgenic maize plants were detected by PCR and bar test strips and results showed that the target gene CSP and marker gene bar were successfully transferred.T0 transgenic maize plants were also hybridized with maize backbone inbred line Zheng 58,Semi-quantitative RT-PCR were performed on the F1 generation maize plants,and the results showed that all 9lines were expressed,L4,L5 and L9 lines with higher expression levels were selected for Southern blotting and chi-square test.Southern blot results showed that the CSP gene had been integrated into the maize genome and all three lines were single copies.The chi-square test results showed that the segregation ratio of offspring was consistent with the Mendel's law of separation of 1: 1.Therefore,these three lines were selected to carry out the drought resistance and cold tolerance physiological experiment at the seedling stage.The results of physiological tests at the seedling stage of the three lines showed that after two weeks of drought stress,the growth condition of the transgenic maize lines wassignificantly better than that of the wild type maize,and the biomass,root length,relative leaf water content and superoxide dismutase activity of the transgenic maize lines were higher than those of the wild type maize,and the content of malondialdehyde was lower than that of wild type maize,indicating that the transgenic plants had better drought resistance than wild type maize;After three days of low temperature stress,the chlorophyll content and superoxide dismutase activity of transgenic lines were higher than that of wild type maize,and the malondialdehyde content was lower than that of wild type maize,indicating that the transgenic maize lines had better low temperature tolerance than the wild type maize.The L9 line with better performance was selected for field drought test.The field experiments showed that under normal growth conditions,there was no significant difference in agronomic traits between transgenic and wild type maize plants;after drought stress,there was no significant difference in plant height,leaf area,panicle diameter,panicle row number and 100 grain weight,and the ear height was significantly lower than that of wild type maize,while the panicle length,grain number per row and panicle weight were significantly higher than that of wild type maize.It can be inferred that,under drought stress,the transgenic maize increased the total grain number by increasing the panicle length and grain number per row,thereby increasing the panicle weight.The above results indicated that overexpression of CSP gene in maize can improve the drought resistance and cold tolerance of transgenic maize plants.