The Mechanism Of Raising Salt Resistance Ability Of Progeny Induced By Salt Stress Of Maize Buds

Soil salinization is the most important abiotic factor affecting plant growth,yield and distribution.Corn,as an important grain and forage as both material and industrial and pharmaceutical raw materials,has relatively high relative yield,but is poor in salt and alkaline resistance,and different varieties of corn are affected by genotypes,morphological traits,internal physiological and biochemical reactions.The sensitivity of salt is also different,and its salt tolerance also different.In this study,a maize Zheng 58 inbred line was used as the experimental material to study the characteristics of morphological and physiological changes at different stages of salt induced by a subculture in different stages of the shoot,using the method of corn shoot tip cultivation.RNA-Seq screened for key salt-tolerant genes,explored the main metabolic pathways for response to salt stress in maize,and improved the salt tolerance mechanism of offspring,explored ways to improve salt tolerance in maize,and used it to create new salt-tolerant maize germplasm.The main findings are as follows:(1)Established a set of salt stress induction system that can complete the entire life cycle from seed to seed.The Zheng 58 corn seeds were first surface-sterilized and the seeds were inoculated into 100 mmol/L Na Cl MS medium with the embryos upward for germination.Obtain shoot tips,Subsequent salt stress was induced in 250 mmol/L and 400 mmol/L Na Cl MS medium for one and twice subculture.After the end of different treatments,the seedlings were transferred to 1/2 MS medium containing 100 mmol/L Na Cl for rooting culture.After hardening seedlings,they were transplanted to the ground and artificial climate chambers,self-crossed and seeded to obtain induced seeds..(2)Salt stress induction has a certain effect on improving seed salt resistance of offspringThe mature maize seeds harvested from salt stress inducing seedlings and control seedlings in an artificial climate chamber were subjected to a germination test.By comparing the results,it was found that the relative single plant growth in the stress induced by the previous salt stress seed was significantly higher than control(P < 0.05).Also had greater performance than the other two materials in relative seedling length and relative root length.Seeds of progeny of seedlings that had been treated with salt stress in the early stage were less inhibited when they encountered adverse stress again.The treatment of salt stress in early stage had a certain effect on improving the resistance of offspring seeds.(3)salt stress induction significantly increased the activity of antioxidant enzymes in seedlings.The activity of SOD,POD and CAT in the salt stress group increased and reached the maximum level in 21 d at one and two subculture by salt stress,and the activity of SOD,POD and CAT in the salt stress group was increased.This time was 3.2,1.8 and 1.7 times higher than that of the control group respectively.The activity of SOD and CAT in the salt stress group showed a tendency to rise first and then decrease,while the activity of POD showed a tendency to rise continuously and to reach the maximum level at 42 d at the 6 time points of the two subculture.Despite the dynamic changes in the activity of three enzymes,the activity of the enzyme remained at a higher level than that of the control group except for 7 day.(4)Significant changes in glutathione expression levels before and after salt stress inductionIn the transcriptome of salt induced subculture,glutathione transferase was significantly enriched in the results of GO analysis.Its function was closely related to the clearance of ROS.33 of them encoded glutathione transferase.The genes play an important role in antioxidant levels.(5)The effects of extracellular regions,thylakoids,and DNA packaging pathways were greatest at the 7 d 14 d and 21 d of salt stress induction.In the results of salt stress induced transcriptome data,analysis of GO enrichment results showed that the extracellular regions was the most affected during the 7 d of salt stress induction,and a large number of genes in the extracellular regions were oxidative and hydrolytic enzymes.It was shown that redox in the extracellular regions was greatly affected during the 7 d stress induction,and also affected the energy metabolism,cellulose and cell wall synthesis process.It was explained that the growth and development of seedlings in the determination of physiological indicators was inhibited.The effects of salt stress on the thylakoids were most significant in the 14 d.The effects on photosynthesis are also significantly enriched.At the 21 d,DNA packaging is the most significant term at this stage.(6)Negative regulation of histone gene participates in response to salt stress inductionThe three pathways of nucleosomes,DNA packaging and protein heterodimer activity induced by salt stress were significantly enriched during the entire induction period.Out of the 103 genes belonging to three pathways,68 encoded different histones.Of the genes,65 were down-regulated,with the largest foldchange-4.8.During the process of salt stress induction,histones are affected,and down-regulation of histone genes plays a more important role in regulation.The expression levels of eight histone genes were verified.The relative expression levels in the adversity environment were also significantly down-regulated,showing the same expression patterns as in the induction process.