| Soil salinization is one of the main abiotic stress that restrains the rice growth.Plant salt tolerance is a quantitative trait controlled by polygenes.So it is significant to discover the quantitative trait loci(QTL)related to salt tolerance and understand the genetic and molecular mechanism of salt tolerance in improving the rice molecular breeding.In this study,a backcross introgression population(BC2F7,226 lines)derived from the cross between Minghui 63(salt tolerance,ST,and the recurrent parent)and 02428(salt sensitive,SS)was used as experimental materials,which was used for ST screening in two consecutive years and four times.The QTL and candidate genes related to ST were detected by genetic linkage map constructed by high throughput SNP molecular markers,metabolome and transcriptome.The main results were obtained as follows:Firstly,a total of 252 QTL related to ST phenotypes were detected by ICIM in four experiments and 11 of them were detected in two or more experiments.The metabolites under control and stress conditions were investigated through gas chromatograph-mass spectrometer.113 metabolites were identified including sugar,amino acid,organic acid and other small molecules.Principal Component Aanalysis(PCA)showed that stress induced significant changes in the content of metabolites in plants.PC1 clearly distinguished the control and salt treated samples which explained 62.6% of the difference in metabolites.The alanine,rhamnose,threonine,sorbose and mannose,etc.were found contributed to PC1 obviously.Secondly,QTL loci were detected in 49,38 and 61 metabolites under the conditions of control,treatment and change ratio,respectively.Among them,2,1 and 5 metabolite QTL,respectively,were identified which can explain more than 40% variations.The PVE of 5-aminovaleric acid(M17)and adenine(M20)loci(q M17-3 and q M20-3)which participating the salinity response were up to 92.5% and 60.3% respectively.Totally,36 important QTL were identified and 27 of them were found influencing the ST phenotype and metabolites simultaneously.In addition,6 of them were newly discovered in this study,namely 2.5-4.5 c M on chromosome1,94.5-96.0 c M on chromosome 3,121.5-122.0 c M on chromosome 5,34.5-36.5 c M and 103.5-114.5 c M on chromosome 7,and 30.5-36.5 c M on chromosome 12.Furtherly,MH63 and two lines,DQ46(ST)and DQ138(SS)with salt-tolerant QTL selected from the population,were used for metabolome and comparative transcriptome analysis.Metabolome analysis showed that the levels of raffinose and maltotriose in MH63 and DQ46 were induced to incease more significantly than that in DQ138.In transcriptome analysis,there were 40 differentially expressed genes in the target QTL including two key genes(Os02g0463401 and Os02g0527200)found in WGCNA analysis and two genes(Os07g0605400 and Os07g0615000)in a newly discovered QTL(103.5-114.5 c M on chromosome 7).Eight genes from the differential expressed were selected with q RT-PCR and the results of seven of them were consistent with that in transcriptomics.Finally,conjoint analysis of transcriptomics and the metabolomics indicated the ST performance of MH63 and DQ46 was related to the better adjustment of osmotic and redox balance which could alleviate stress damage through involving linoleic acid and ?-linolenic acid metabolism,glycosphingolipid biosynthesis,thiamine metabolism,carotenoid biosynthesis,ABC transporters and aminoacyl-t RNA biosynthesis pathways.Moreover,there were three different responsive pathways between MH63 and DQ138 which including linoleic acid metabolism pathway,?-linolenic acid metabolism pathway and biosynthesis of amino acids pathway.The results presented in this study would provide valuable information for further elucidating the molecular mechanisms underlying rice ST. |
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