| About 20%-50%of the world’s arable land is affected by salinization.Countries around the world are actively studying and exploring the control measures of soil salinization,so as to improve the effective use of soil resources,improve the ecological environment,and promote the sustainable development of agriculture.Screening and creating wild and cultivated plants which are possessed salt-tolerant genes and potential economic value for adaptive planting,and excavating the plant salt-tolerant genes can not only enrich plant diversity of the regional soil condition,but also greatly improve the economic benefits of saline-alkali land,improve the ecological environment of saline area.Thus,it is of great significance to strengthen the ecosystem resilience,promote farmers’economic income steadily,and develop rural economy.Sorghum(Sorghum bicolor(L.)Moench)is the fifth largest crop in the world.It is a C4 crop of annual gramineae,and is a typical ecological crop with characteristics of drought,waterlogging,salt,alkali,and barren resistance.This research evaluated the salt resistance of 35 sorghum materials under salt stress condition by determing the related index.Based on the evaluation results,the typical grain sorghum and sweet sorghum materials were selected for the salt solution treatment.After 0,48,72 h,the transcriptome sequencing analysis was conducted to compare the differences between sweet sorghum and grain sorghum with different degree of salt tolerance.The salt tolerance related genes of sorghum were mined and cloned.Dihydroflavanol 4-reductase(DFR),a key gene for anthocyanin synthesis,was cloned by mining salt tolerance related genes in sorghum.The subcellular localization of the gene is present in cytoplasm.The main research results are as follows:1.After salt solution treatment,the germination potential,germination rate,bud height,root length and seedling forming rate of 35 sorghum materials were determined,and the salt tolerance was evaluated.According to the strength of salt resistance,the 35 materials were divided into 4 grades,including 5 materials with salt resistance of grade Ⅰ,9 materials of grade Ⅱ,10 materials of grade Ⅲ,and 11 materials of grade Ⅳ.The evaluation system of sorghum salt tolerance was optimized.2.The inhibitory effects of salt stress on GR,VI,RDW and RL were significantly different between GZ and HN 16.Salt stress had little inhibitory effect on GZ seedlings,and GZ had better tolerance to salt.A total of 32,500 transcripts(with an average length of 2100bp)were obtained by transcriptome sequencing,with an average of 836 new genes in each transcriptome library.By screening differential genes and functional annotation analysis,8 up-regulated genes and 37 down-regulated genes related to salt tolerance were found.The expression levels of four genes in GZ were higher than that of HN 16.corresponding to the genes of DFR,LDOX,ANR and F3H in flavonoid biosynthesis pathway.The two genes encoding POD and CCR are involved in lignin biosynthesis during the conversion of phenylalanine to phenylpropane.KEGG analysis showed that 45 genes were mainly involved in flavonoid biosynthesis and phenylalanine metabolism pathway.Based on transcriptome data,a GRF gene family related to resistance was selected for identification,and the analysis results showed that most of the genes in this gene family were more actively expressed under salt stress.3.The content of tannins and total phenols in roots of the two sorghum varieties increased after salt stress,and the content in sweet sorghum was higher than that of grain sorghum Henong 16.The change of tannins and total phenols content before and after salt treatment was positively correlated with salt tolerance of the sorghum.The high expression of DFR,LDOX,ANR and F3H genes in the flavonoid biosynthetic pathway promoted the accumulation of tannin and total phenolic substances and improved the salt tolerance.The qRT-PCR results showed that the 4 candidate genes were highly expressed in GZ under salt stress.The results were consistent with the results of transcriptome sequencing.4.The phylogenetic and evolutionary analysis of DFR gene showed that the homology of DFR gene was high in sorghum and sugarcane.The gene was cloned in GZ and transfected into Arabidopsis thaliana via Agrobacterium-mediated transfection.Positive plants were selected for self-crossing stabilization.T2 transgenic Arabidopsis thaliana was subjected to stress treatment with 0.8%salt solution,and the results showed that:The salt tolerance of transgenic Arabidopsis thaliana was increased,and the salt tolerance was better than that of wild-type Arabidopsis thaliana.The subcellular localization of the gene is present in cytoplasm and other organelles. |
