| Cotton is a major economic crop,although important progress has been made in the research on the physiological and biochemical mechanisms of cotton fiber development,its molecular mechanism is still unclear.Rapid and effective quality improvement is a serious challenge in cotton production.Further exploration of the genetic characteristics of important agronomic traits in Gossypium hirsutum L.× Gossypium barbadense L.backcross populations and mining of genes related to excellent fiber quality provide the possibility to solve this problem.In this study,the backcross population materials constructed from Xinjiang’s self-bred upland cotton Line 9 and sea island cotton Xinhai 16 were used as the research objects.The important agronomic traits and fiber quality traits of the sea and land populations were determined,and the backcross progeny were determined by various analyses.The relationship between agronomic traits and fiber quality of the population was discussed.On the basis of identifying the fiber quality traits of the population for many years,the fiber length extreme materials were screened,and the QTL segments related to fiber length were rapidly obtained by BSA sequencing technology.Combined with the transcriptome sequencing of cotton fiber development,key candidate genes were mined and analyzed.The signaling pathways involved are predicted.The main findings are as follows:(1)The correlation analysis of the main characters in multiple environments of the progeny population of the sea-land backcross showed that the main agronomic traits and fiber quality traits were extremely significantly correlated in each environment.Fiber length(FL),fiber strength(FS)and fiber uniformity(FU)in the offspring population were extremely significantly positively correlated with plant height(PH),fruit branch number(FBN),effective branch number(EFBN),boll number(TBN)and effective boll number(EBN);determined by principal components 3principal components;using multivariate stepwise regression analysis,the best model of fiber quality and main agronomic traits can be obtained.According to this model,the fiber quality of a certain line in the sea and land population can be predicted;The population is divided into 5categories,and the population strains can be screened according to the breeding objectives in the actual breeding work.(2)Combined with the fiber length phenotype data for many years,30 lines with long fiber(including HL-9,HL-62 and HL-194,etc.)and 30 lines with short fiber(including HL-34,HL-78 and HL-159,etc.)were screened out.The screened extreme materials and parents were used to construct the fiber length extreme pool,and the candidate segments related to fiber elongation were correlated by BSA-seq.The long correlated region,totaling 1.81 Mb,contained 149 candidate genes.(3)The long-fiber line L and the short-fiber line S of the progeny of the Gossypium hirsutum L.× Gossypium barbadense L.backcross populations were collected for RNA-seq in the fiber tissues of 0 DPA,5 DPA,10 DPA and 15 DPA.Four time points of fiber development identified992/821,1668/953,1018/585 and 937/535 genes with up-or down-regulated expression,respectively.Using STEM software analysis,it was identified that the long fiber line L and the short fiber line S have a common enrichment profile19,including 2099 genes,and GO annotation classification was performed,and it was found that the differentially expressed genes were mainly involved in cellular processes and metabolic processes.Fifteen expression modules associated with fiber development time points were detected using WGCNA,of which four important modules were identified as being strongly correlated with fiber elongation(correlation index >0.8),containing a total of 1591 genes.21 hub-gene were identified in these modules,which encode 12 proteins and 7 enzymes,mainly involving heat kinase,ABC transporter protein,mitogen-activated protein kinase,glycosyltransferase,hydrolase and cellulose synthase.(4)According to the comparison between the 149 candidate genes located by BSA-seq and the 1591 genes obtained by transcriptome analysis,a total of 13 key candidate genes.Combined with q RT-PCR technology,it was screened that the Ghb HLH148 gene had extremely significant differences in the expression of 10-15 DPA in fiber development in the parental and extreme progeny;Gh CMB1 had extremely significant differences in the expression of 0-10 DPA in parental cotton fiber development,The extreme progeny had extremely significant differences in 10 DPA expression in fiber development;Gh Togaram1 gene had significant differences in parental 0 DPA,5 DPA and 25 DPA expression,and in progeny 5 DPA expression.Using the fibrous tissue of parental lines 9 and Xinhai 16 as templates,3 gene coding sequences were cloned respectively.Bioinformatics showed that b HLH148 gene has 1 amino acid difference between its parents and belongs to b HLH transcription factor;CMB1 gene also has 1 amino acid difference in both parents.The difference of 1 amino acid belongs to the MADS-box transcription factor;Togaram1 gene has2 amino acid difference between its parents and belongs to the CLASP＿N gene family.(5)The yeast transcriptional activation activity analysis showed that Ghb HLH148 transcription factor and Gb CMB1 transcription factor did not have transcriptional activation activity,while Gbb HLH148 transcriptional factor and Gh CMB1 transcriptional factor had transcriptional activation function.The silencing vectors of Ghb HLH148,Gbb HLH148,Gh CMB1,Gb CMB1,Gh Togaram1,and Gb Togaram1 genes were constructed in both parents.The expression levels of all silenced genes were significantly decreased.These six genes may affect the development of cotton fibers by regulating the expression of fiber cell elongation-related genes.In addition,it is presumed that the b HLH148 gene It may be through the expression of Gh GAI1,Gh HD1 and Gh RDL1 genes that mediate the gibberellin metabolic pathway to affect the length of the amphiphilic fibers. |
PDF Full Text Request