SEF,a Component Of SWR1 Chromatin Remodeling Complex,Regulates Salt Tolerance In Arabidopsis

Salt stress seriously affects plant growth and crop yield through ion toxicity and osmotic stress.It is of great significance to study the molecular mechanism of salt tolerance in plants for the improvement of plant varieties.In Arabidopsis,ATP-dependent SWR1 chromatin remodeling complex consists of three major proteins,including PIE1,SEF,and ARP6.SWR1complex can replace H₂A with histone H₂A.Z to produce nucleosome variants and activate gene expression.Previous studies have shown that PIE1,SEF and ARP6 delay Arabidopsis flowering by promoting the expression of FLC,MAF4 and MAF5.However,the roles of PIE1,SEF and ARP6 in plant stress resistance remain unclear.In order to further understand the function of SEF in plant response to stress,the molecular mechanism of SEF regulating salt tolerance in Arabidopsis thaliana was studied by using T-DNA insertion mutant of SEF gene（sef-2）.The main results are as follows.1.The sef-2 mutant enhanced the salt tolerance of arabidopsis thaliana.125 m M Na Cl was used to stress arabidopsis thaliana seedlings.The relative root length of the mutant sef-2was similar to that of WT.However,the relative fresh and dry weight of aboveground parts of the sef-2 mutant increased significantly.These results suggest that the sef-2 mutant presents a salt-tolerant phenotype.2.The Sef-2 mutant enhances the penetration resistance of arabidopsis thaliana.The sef-2mutant was treated with mannitol under osmotic stress.Compared with WT,the relative fresh weight of aboveground parts of sef-2 mutant increased significantly.The results showed that the mutant of sef-2 could enhance the tolerance to osmotic stress.3.The sef-2 mutant is sensitive to lithium ions.The stress was treated with 12.5mm Li Cl and 3.75mm Cs Cl.It was found that the relative root length of sef-2 mutant was significantly reduced compared with WT under Li Cl stress.The results showed that lithium ion had ion toxicity to the sef-2 mutant.The SEF-containing plant binary vectors are constructed.To perform complementary analysis,we construct SEF-containing plant binary vectors,including35S:SEF_CDS-GFP and SEFpromoter:SEF_CDS-GFP in p Cambia 1300.4.A plant binary expression vector containing SEF gene was constructed.In order to further determine that the mutation of sef-2 is the cause of salt tolerance phenotype,the plant binary expression vectors 35S:SEF_CDS-GFP and SEFpromoter:SEF_CDS-GFP were constructed by DNA recombination technology.5.Transgenic lines of Arabidopsis thaliana were created 35S:SEF_CDS-GFP and SEFpromoter:SEF_CDS-GFP transformed Arabidopsis thaliana were developed by Agrobacterium-mediated flower dipping genetic transformation.At present,transgenic homozygous lines have been screened for salt tolerance analysis.6.The molecular mechanism of SEF regulating salt tolerance in Arabidopsis thaliana was preliminarily revealed.Semi-RT-PCR and fluorescent quantitative RT-PCR were used to detect the expression of salt tolerance related genes in sef-2 and WT under Na Cl stress.The results showed that the up-regulation of SOS1 expression in sef-2 mutant was the main molecular mechanism of salt tolerance in sef-2 mutant.The down-regulation of NHX8expression in sef-2 mutant is the main reason for the sensitivity of sef-2 mutant to Li⁺.The expression level of NHX8 was down-regulated in sef-2 mutant,which reduced the reverse transport of Li⁺.This may be the main molecular mechanism of the sensitivity of sef-2 mutant to Li⁺.