Study On Drought And Cold Resistance Function Of GthCBF4 And GhGLK1 In Cotton

With the global warming and the aggravation of extreme weather events,drought and low temperature have become one of the common abiotic stresses in the main cotton producing areas,seriously affecting the growth,development and yield of cotton.Cotton is one of the most important fiber producing crop specifically in China.Various biotic and abiotic factors lead to lower yield of cotton.Drought and low temperature stresses are the most prominent abiotic stresses affecting cotton.Breeding cotton germplasm resistant to such abiotic stresses is the need of time.Wild cotton being exposed to harsh environments have more potential to cope with biotic and abiotic stresses.Exploiting wild material to induce resistant germplasm would be of greater interest.Currently,we performed transcriptome in Gossypium thurberi under cold stress.On the basis of expression analysis GthCBF4 was selected as the candidate gene linked to cold stress tolerance.Furthermore,we also did overexpression in Arabidopsis thaliana to validate the role of GthCBF4 under cold stress.Moreover,we also identified a candidate gene GhGLK1 for both cold and drought stress tolerance on the basis of QTL mapping by using a BC₂F₂population created by crossing upland Gossypium hirsutum and Gossypium tomentosum.Further functional characterization was performed to confirm the potential role of GhGLK1 in drought stress tolerance.Following are the main results of current research work:1.CBF(C-repeat binding factors),an important factor in plant cold regulation pathway,has been widely studied in many plants,but given less emphasis in cotton.In this study,based on the genome information of existing diploid cotton species,the whole genome of CBF gene family was identified and analyzed.In total 29,28,21,25,30,26 and 15 members were identified in the genomes of G.herbaceum,G.arboreum,G.thurberi,G.raimondii,G.turneri,G.longicalyx and G.australe,respectively.These members can be divided into 7 groups according to the results of phylogenetic analysis.The results of gene structure and chromosome distribution analysis showed that the gene structures of closely related members were similar,indicating that the above genes were highly conservative in the process of evolution.Cis-acting element analysis showed that members of the CBF family may be involved in response to low temperature stress in cotton.An up-regulated gene GthCBF4(Gthu17439)under cold stress was screened by RNA-seq and qRT-PCR analysis.It was overexpressed in Arabidopsis thaliana.Under cold treatment at-15?,the GthCBF4 overexpression plants showed more adaptability with less ROS accumulation,less leaf damage thus,indicating that overexpression of GthCBF4may improve the cold tolerance of plants.2.Golden2-like(GLK)gene,which belongs to the GARP family,is a kind of plant-specific transcription factors.Preliminary functional verification analysis of GhGLK1(Gh?D01G0183.1)gene was carried out.GhGLK1 was silenced by virus-induced gene silencing(VIGS).The wilting of cotton leaves in plants with silenced GhGLK1 gene was more serious under drought and cold treatments.Compared with non-silenced,the cell damage of cotton with silenced GhGLK1 gene was more serious,the accumulation of ROS was more,and the tolerance of plants to drought and cold stress was lower.The overexpression of GhGLK1 in Arabidopsis thaliana showed that the plants overexpressing GhGLK1 showed more adaptability than the wild type after drought and cold treatments.The results of trypan blue and DAB staining showed that after drought and cold treatment,the leaf damage in GhGLK1overexpressed plants was less as compared to the wild type,and the ion permeability was also lower.This study suggested that GhGLK1 gene may be involved in the regulation of drought and cold stress response in cotton.Our current finding adds significantly to the existing knowledge of cold and drought stress tolerance in cotton and further deep molecular analysis are required to understand the genetics and molecular mechanisms underlying drought stress tolerance in cotton.