Genome-wide Analysis Of Three Fatty Acid Biosynthesis Gene Family And In Gossypium Raimondii And The Expression Pattern Of Their Corresponding Orthologs In Tetraploid Cultivated Cotton(G.Hirsutum)

Cotton(Gossypium spp.)is the most important fiber plant,and is also a significant oil crop.Fatty acid synthesis have important function in both regulating fatty acid cotent,composition and fiber development,disease and stress resistance in cotton.In recent years,the development of molecular biology research in cotton is very fast,especially in improving the fiber yield and quality,but the study of reforming the cotton seed oil cotent and composition is very little.In this study,three fatty acid biosynthesis family genes were identified.Phylogenetic relationships,gene structures and expression parrerns were also investigated.The results as follows:1.We identified 8 LPAT genes,9 SAD genes and 19 FAD genes from G.raimondii genome.They were named GrLPAT1-GrLAPT8,GrSAD1-GrSAD9 and GrFADl-GrFAD19,respectively,accorded by the location on chromosomes.Phylogenetic analysis indicated that LPAT,SAD and FAD family genes can be sorted into four groups,two groups and two groups,and distributed in 6 chromosomes,5 chromosomes and 11 chromosomes,respectively.The LPAT genes in cotton have two or more introns;? class of SAD genes have two introns,except GrSAD1,and ? class have only one intron;? a class of FAD genes have 7 introns,? b class gene have no intron,besides GrFAD17 and GrFAD18 have 9 and 2 introns,respectively,Among ? class of FAD genes,four have introns,the other four do not contain introns.The diversity of the gene structure,may be associated with the function of the genes.2.We examined the expression pattern of those gene in root?stem?leaf?seed and fiber at different development periods of G.hirsutum acc.7235 using the qRT-PCR.The results revealed that those genes have different expression patterns.SAD2?SAD4 and FAD19 showed the preferential expression in seeds.Eight LPAT genes were highly expressed in fiber development stages,and also SAD9?FAD3?FAD6?FAD7?FAD 13 and FAD16 genes,implying that those genes may involved in regulating of cotton fiber development.3.Futher analysis found that,the expression level of SAD2,SAD4 and FAD19 in high-oil cotton young ovules was significant higher than that in low-oil cultivars,especially at late stage of seed development.we cloned those genes in high-oil cultivars and low-oil cotton.And then,we found the A genome sequence of SAD4 gene have 2 sequence variations between high-oil cultivars and low-oil cotton by sequencing.Based on the sequence difference,the association analysis with characters data of fatty acid and fiber in natural population(286 cultivars)were carried on.The results indicated that there was highly significant association between S2 and fiber micronaire,seed content of oleic,linoleic and O/L at P<0.05 or P<0.01 level.After further analysis and validation,the results could be used for molecular breeding design in cotton fiber and seed oil quality improvement.