Molecular Identification And Study On Salt Tolerance At Seedling Stage Of Transgenic ABP9 Maize Lines

Soil salinization has become the increasingly serious worldwide ecological problem that not only threats the limited land resources on which human beings live but also severely restricts the agricultural production.Maize is one of the three major grain crops in the world and occupies an important position in Chinese national economy(Zea mays L.).Nevertheless,the salt tolerance of maize is relatively worse,which restricts the planting area and yield of maize.In order to improve the salt tolerance of maize varieties for larger planting scopes and stronger adaptability,there invented and prepared the transgenic ABP9 maize plants based on Zheng 58 in the laboratory.In this study,the molecular identification is conducted on transgenic ABP9 maize plants.Hoagland nutrient solution hydroponics is used to conduct the NaCl stress treatment on transgenic ABP9 maize plants and those free of transgenic materials so as to compare the differences in the physiological indicators and gene expression during the seedling stage between the two and preliminarily study the salt tolerance system.The main study results are shown as below:1.Through PCR test,there are 9 and 6 plants identified as transgenic positive plants among Pubi-ABP9 and Pabp9-ABP9 transgenic materials,respectively.The qRT-PCR results showed that the expression levels of ABP9 in transgenic positive plants increased in which the expression levels of the two overexpression plants,J8-2 and J20-12-3,are relatively higher.The results of Southern blot and Western blot prove that gene ABP9 is integrated into the maize genome in a single copy and is successfully expressed.2.Hoagland nutrient solution hydroponics is used to conduct a series of salt stress experiments on transgenic ABP9 maize plants and negative control plants.The results show that,compared with the negative control plants,chlorophyll contents,Fv/Fm,osmotic regulators and antioxidant enzyme activity of transgenic maize seedlings under salt stress and relative water content of leaves during the recovery process after salt stress are significantly improved.Contrarily,the malondialdehyde content,relative conductivity and ROS content of transgenic maize seedlings under salt stress are lower than those of the negative control plants.Based on the summary of various physiological indicators,ABP9 overexpression exactly improves the salt tolerance of maize.3.1075 potential ABP9-regulated genes that respond to salt stress are eventually screened with analysis on transcriptome sequencing results and discovery of differentially expressed genes.qRT-PCR test is conducted on some genes whose results are basically the consistent with the expression tendency of differentially expressed genes in the analysis on sequencing results,indicating that the data reliability of sequencing results is relatively high.As found by GO functional enrichment analysis,these genes significantly are enriched in the biological process,such as response to abiotic stresses and removal of reactive oxygen species.Hence,it can be deduced that the enhanced expression of these stress resistance related genes may be the key to improving the salt tolerance of transgenic maize plants.In conclusion,the integration of ABP9 gene enhances the expression and improves the salt tolerance of transgenic maize,which provides reference and theoretical support for further studies and new germplasm for salt tolerance breeding of maize.