Preliminary Study Of Salt Tolerance Molecular Mechanism And Mining Functional Gene Of Seedling Stage In Gossypium Hirsutum Based On Transcriptome

Now,it is an important trend of cotton industry structure adjustment to plant cotton in saline-alkali in China.Seedling stage is one of the key periods of salt tolerance in cotton,but the research of salt tolerance mechanism is relatively slow in cotton.In this study,three salt-tolerant varieties(ND13,Emian 9 and Ekangmian 3 with relative survival rate were 56.7 %,73.3 % and 50.9 %,respectively)and three salt-sensitive varieties(Jinmian 12,Lumian 14 and Zhong 078 with relative survival rate were 34.04 %,32.95 % and 33.30 %,respectively)were treated at 3 time points of 0 h,0.5 h(fast response stage)and 5 h(specific response stage)with 150 mmol/L NaCl in the three-leaf stage.The lncRNA sequencing were operated for these 18 samples,and the salt tolerance function of key candidate gene was identified at seedling stage.The main results were as follows:1.Two key periods of rapid response and specific response were identified in six varieties under salt stress in this study.Under salt stress 0.5 h,the leaves of the salt sensing group became soft and drooping,but there was no obvious change in the salt tolerant group.Therefore,it was determined that this time was the rapid response stage.Under salt stress 5 h,the stem of the salt sensing varieties were obviously lodging,and the salt tolerant group was slightly softened,and it was determined that this time was the specific response stage.2.Transcriptome sequencing was performed on 18 samples of six varieties under salt stress 0 h,0.5 h and 5 h.A total of 1 637 954 150 clear read data were obtained,of which 11 624 lncRNAs and 14 933 differential genes were identified.The differential expression analysis between salt tolerance group and salt sensitive group showed that 196 up-regulated expression and 223 down-regulated expression of lncRNAs were identified at salt stress 0 h.And 2 790 up-regulated expression and 1 543 down-regulated expression of mRNAs were identified at salt stress 0 h.At the rapid response stage,there were 200 up-regulated expression and 253 down-regulated expression of lncRNAs,and there were 3 747 up-regulated expression and 2 262 down-regulated expression of mRNAs.At the specific response stage,a total of 187 up-regulated expression and 241 down-regulated expression of lncRNAs,and 2 201 up-regulated expression and 2 390 down-regulated expression of mRNAs were identified.3.Compared with 0 h,134 and 136 differential up-regulated expressions lncRNAs were screened at the rapid response stage and the specific response stage respectively,of which 34 were the common expressed at two stages.Among the down regulated differential expressions lncRNAs,a total of 189 and 193 lncRNAs were screened at the rapid response stage and the specific response stage respectively,of which 27 were the common expressed at two stages.Within the up-regulated differential expressions mRNAs,2 561 and 1 584 mRNAs were screened at the rapid response stage and the specific response stage respectively,of which 554 were common differentially expressed at two stages.Among the down-regulated differential expressions mRNAs,there were 1 731 and 2 178 mRNAs at the rapid response stage and the specific response stage respectively,of which 227 were common differentially expressed at two stages.4.At the rapid response stage,it was identified that 26 targeting co-localized specific differential expressions mRNAs and 19 targeting co-expressed specific differential expressions mRNAs for up-regulated lncRNAs.And we obtained 68 targeting co-localized specific differential expressions mRNAs and 76 targeting co-expressed specific differential expressions mRNAs for down-regulated lncRNAs.At the specific response stage,we obtained 51 targeting co-location differential expressions mRNAs and 13 targetiong co-expression differential expressions mRNAs for up-regulated lncRNAs,and obtained 67 targeting co-location specific differential expressions mRNAs and 110 targeting co-expression specific differential expressions mRNAs for down-regulated lncRNAs.5.The GO analysis of differential expressions mRNAs showed that the genes related to redox process and hormone metabolism were significantly enriched in biological processes at the rapid response stage.At the specific response stage,the related genes of photosystem,photosynthetic membrane and vacuolar proton ATPase were significantly enriched in the cell components.KEGG analysis showed that differential expressions mRNAs were significantly enriched in the biosynthesis and metabolism of amino acids,starch,sucrose and other organic compounds at the rapid response stage.At the specific response stage,the differential expressions mRNAs were significantly enriched in plant hormone signal transduction,glycolysis,photosynthesis and pyruvate metabolism.6.The co-localization differential expression gene GhSaltR1(GenBank accession number: MK578764)with lncRNA was screened and cloned in this study.VIGS(virus induced gene silencing)assay shown that VIGS-GhSaltR1 plants had lower salt tolerance than wild type plants of ND13.RT-PCR analysis showed that the silence efficiency of GhSaltR1 gene was 82 %.It is preliminarily proved that GhSaltR1 gene played an important role in the salt tolerance reaction of cotton seedlings.In conclusion,a total of 134 up-regulated differential expression lncRNAs and 189 down-regulated differential expression lncRNAs,and 2 561 up-regulated differential expression and 1 731 down-regulated differential expression mRNAs were identified at the rapid response stage.One hundred and thirty-six up-regulated differential expression lncRNAs and 193 down-regulated differential expression lncRNAs,and a total of 1 583 up-regulated differential expression and 2 178 down-regulated differential expression mRNAs were identified at the specific response stage.And GhSaltR1 was firstly verified to play an important role to salt tolerance response at seedling stage in cotton.