Genome-wide Identification Of Acyl-CoA-binding Protein (ACBP) Gene Family And Their Functional Analysis In Abiotic Stress Resistance In Cotton

Cotton is an important economic crop,affecting many aspects of human life.Discovery,domestication,cultivation and genetically improvement of cotton is an important epitome of the progress of human civilization.But with the increasing influence of human activity in the world,human living and survival environment is deteriorating,exhibited by the expanded scope of the impact of extreme weather and terrific conditions.The changed environment also exerts great challenge to human agricultural production.In the face of reduction of arable land,cotton planting is gradually giving way to wheat,rice and other food crops,and transferred to the more arid,saline-alkali land Therefore,enhancing cotton rsistance and tolerance to abiotic stresses become an important work for cotton breeding.On the other hand,as a relative strong abiotic stress resistant crop,cotton has greater potential for abiotic stress resistant breeding.Acyl-coenzyme A binding protein(ACBP)encoding genes are important functional genes to transfere coenzyme A esters and phospholipids.Via regulating metabolism of unsaturated fatty acids,acyl-coenzyme A library of fatty acid β-oxidation and vesicle transport,the ACBPs can participate in complex physiological processes in plant,such as biotic and abiotic stress response,membrane repairing and growth and developmental process.Currently,researchers have discoveried and charaterized ACBP genes in many plants,but little is known in cotton.Based on the genomic sequence information of Upland cotton G hirsutum TM-1,G.raimondii and G arboreum.We clarified the biological information of the 21 ACBP genes in G hirsutum TM-1 by phylogenetic analysis and classification in this study.We determined the candidate ACBP genes involved in abiotic stress resistance by transcriptome analysis and qRT-PCR data.Furthermore,the biological functions of these candidate gens in regulating cotton drought and saline-alkaline resistance are verified by Virus Induced Gene Silencing(VIGS)technology.All the experimental results are as follows:1.We identified 21 ACBP sequences in the allotetraploid cotton TM-1(AADD)genome database,where At-subgroup containing 10 ACBP sequences,distributed in five At-sub chromosomes,and Dt-subgroup containing 11 ACBPsequences,distributed in four At-sub chromosomes,with one sequence was not confirmed.Ten and eleven sequences were identified in diploid G ramondii and G arboreum,respectively,distributed in six chromosomes.CDS nucleotide sequences of ACBP family members ranged from 267 to 2109bp,and the corresponding amino acid sequences ranged from 88 to 702aa.According to the results of cluster analysis and phylogenetic tree of the Arabidopsis thaliana ACBP genes,the 21 amino acid sequences of Upland cotton were divided into 4 classes:Ⅰ～Ⅳ.2.The expression pattern of ACBP genes in various tissues of Upland cotton was investigated by transcriptome analysis.It was found that the expression of the ACBP genes is quite different in different tissues,organs and developmental ovules and fibers.GhACBP6 exhibited the highest expression in all cotton tissues.By examining the expression pattern of ACBP genes under four different stress conditions,salinity,drought,low temperature and high temperature,we identified that GhACBP3 and GhACBP6 subclass genes play important roles in cotton abiotic stress resistance.The expression pattern of these two subclass genes were further detected by qRT-PCR analysis under hormone treatment.The results demonstrated that GhACBP3 and GhACBP6 genes could be induced by many hormones,indicating the involvement of these two subclass genes in physiological processes controlled by phytohormone.3.We validated the functions of GhACBP3 and GhACBP6 under drought and saline-alkaline stress by VIGS technology.The results showed that gene silencing of GhACBP3 and GhACBP6 resulted in wilting cotton seedlings under drought treatment,crinkled last leaf,yellow spot forming leaves,and slowed plant growth under salt treatment.In addition,compared to the control,the plant height and dry matter accumulation was significantly decreased in gene silencing plants.The superoxide dismutase activity and peroxidase activity were significantly reduced,but the harmful malondialdehyde content was increased.These results further showed that GhACBP3 and GhACBP6 play important roles under salt and droght stress in Upland cotton.Taken together,this study showed that the ACBP family genes played important roles in cotton development.GhACBP3 and GhACBP6 genes could respond to abiotic stress and hormonal treatment.VIGS results exhibited the requirement of GhACBP3 and GhACBP6 genes in Upland cotton drought and saline-alkaline resistance.