Evaluation Of Heat Tolerance And Analysis Of Allele Variation Of Heat Tolerance Candidate Gene In Flowering Chinese Cabbage

Flowering Chinese Cabbages is an important economic vegetable originating in southern China.In the high temperature and rainy season in midsummer,flowering Chinese Cabbages encounter different heat stress,which results in a large number of deaths and yield loss.In recent years,with the continuous development of agriculture,it has become an urgent task to cultivate new varieties.At present,the study of high temperature tolerance of flowering Chinese cabbages mainly focuses on agronomic traits and biochemical aspects.There are few reports about heat stress of molecular mechanism in flowering Chinese Cabbages.According to this,this paper collects a large number of materials,planting in different seasons,compared and screened heat tolerance indicators,and classified 200 materials by heat tolerance.Based on the transcription group sequencing data of different heat-tolerance varieties,the allelic mutation SNPs were detected in candidate genes which may lead to the different in heat tolerance.These results may help a theoretical basis for the heat-tolerance classification,heat-stressed genes and the molecular mechanism.The main results are as follows:1.Eleven agronomic traits related to heat stress were measured in high temperature summer in Ningxia during 2018 and 2019.As the same time the same materials planted at normal temperature in Guangzhou's autumn were used as controls By eliminating abnormal indexes and screening indexes with variation coefficient(CV?15%)as the 9 main indexes to evaluate the heat tolerance of Flowering Chinese cabbage.In the comprehensive evaluation value of heat tolerance(D),the coincidence rate of the two different indexes is lower,and the 9 main indexes can better evaluatethe heat tolerance of Flowering Chinese cabbage.According to the clustering analysis,4 clustering indexes of 9 main indexes and all 11 indexes calculation by fuzzy membership function and comprehensive evaluation.200 varieties were classified into4 classes: most stronger heat-tolerance,stronger heat-tolerance,mid-level heat tolerance and heat sensitivity.2.The different heat-tolerance varieties were sequenced with the reference genome,and a total 317,852 SNPs were detected from 8 transcriptome,with an average of 7.75 SNPs per gene locus.SNP mutations are mainly of conversion type and occur in the exons.The number of SNPs is the most in chromosomes A09,the least in A02,the most densest in A06,the most sparsest in A04.All snp-containing genes were subjected to GO functional annotation and KEGG enrichment analysis,and the results showed that such genes were involved in a large number of cell metabolism,biosynthesis process,primary metabolic process and other stress reactions,such as stimulus reaction,oxidation reaction,catalytic reaction and signal transduction.3.94 homozygous SNPs were obtained and distributed on 48 candidate genes.There were 46 amino acid synonymous mutations and 48 amino acid non-synonymous mutations.Most of the GO functions and KEGG pathways of the candidate genes are distributed in the secondary items of cell components,cell parts and organelles;cellular processes,metabolic processes and stress responses in the biological process category;protein binding and catalytic activity in the molecular function category.The GO function and KEGG pathway classified candidate genes with non-synonymous mutations into 5 and 4,respectively.The GO secondary items were metabolic process,single biological process,immune system process andcatalytic reaction.The secondary terms of KEGG pathway are carbohydrate metabolism,cofactor and vitamin metabolism,amino acid metabolism and folding,sorting and degradation.4.Using bioinformatics and molecular techniques,two candidate genes(IDD7and PP2C77)were cloned and analyzed.The result found that they had many types of variation in four materials,presumably related to differences in heat tolerance.The basic physical and chemical and analysis of evolutionary relationship in representative species find that IDD7 is generally conservative in both species and out of species,and PP2C77 is highly unconservative in interspecies and out-of-species.Motif structure and amino acid homologous analysis showed that PP2C77 protein has the height homologous with ABI 2 protein,may use ABA(Abscisic acid pathway)pathway;IDD7 protein has the height homologous with At IDD1 and At IDD2 protein,presumably use flowering pathway in gibberellin signal,let the vegetable early flowering,in order to deal with the stress environment.