Functional Verification Of GhGGB And GhROP8 In Drought Resistance Of Cotton

Cotton is the largest cash crop of agricultural products in China,and it is also an important commodity involving textile and fine chemical raw materials.Among all cotton producing areas in China,Xinjiang has the largest cotton production area,but the cotton is often subjected to drought stress due to the lack of precipitation in Xinjiang,resulting in a sharp decline in its total output.Therefore,it is very important to study the mechanism of drought resistance in cotton breeding.Protein isoprene modification is a class of lipid modifications after protein translation.Previous studies have found that this modification is closely related to drought resistance of plants,and GGB gene,as theβ-subunit encoding type I protein geranyl transferase,is also involved.In Arabidopsis thaliana,GGB gene mutation enhanced drought resistance,and phenotypic differences between the mutant plants and the wild type were not significant.Small G protein ROP is a plant specific Rho subfamily,involved in signal transduction,drought,high/low temperature,salt and other abiotic stress and disease resistance responses in plants.Previous laboratory studies have found that there is an interaction relationship between Gh GGB and Gh ROP8.Therefore,according to the Gh GGB and Gh ROP8 genes obtained in the laboratory in the early stage,this study used the VIGS technology to preliminarily analyze and identify the drought-resistant functions of these two genes in cotton,and the main results are as follows:1.Twelve cotton varieties with different drought resistance were selected,and q RT-PCR was used to detect the expression of Gh GGB gene in the root,stem and leaf tissues of different cotton varieties.The results showed that the Gh GGB gene was in each tissue of different drought-resistant cotton varieties.All have expression,but no specific expression.2.Using China Cotton 35 as the material,water treatment as control,q RT-PCR was used to detect the expression of Gh GGB gene after different stresses.The results showed that the expression of Gh GGB gene changed after drought,high salt,low temperature and Verticillium dahliae stress.Among them,the expression of the target gene under drought stress gradually increased with the extension of the stress time.3.The silencing vector of Gh GGB and Gh ROP8 genes was constructed and infected cotton TM-1plants.When the leaves of the positive control group showed obvious albino phenotype,q RT-PCR was used to detect the silencing efficiency of the target gene.The results showed that compared with the control plants,the expression of the target gene in the silent plants was significantly suppressed,indicating that Gh GGB and Gh ROP8 were silenced,and silent plants were obtained.4.The function of Gh GGB and Gh ROP8 genes in drought resistance mechanism of cotton cultivar TM-1 was studied by VIGS technique.After the positive plants showed albinism phenotype,the plants of the Silent Group（TRV:Gh GGB、TRV:Gh ROP8）and the Control Group（TRV:00）were treated with normal and drought stress,and the phenotypic differences of the two groups were observed on different days（5,10 and 15 d）.The changes of electrolyte permeability,relative water content,contents of proline（Pro）,malondialdehyde（MDA）,chlorophyll,soluble sugar（SS）and hydrogen peroxide（H₂O₂）in plants under normal and drought treatment were determined,and the activities of peroxidase（POD）and catalase（CAT）were compared.The results showed that the phenotypes of Gh GGB and Gh ROP8 silenced plants were significantly different from those of the control plants after drought treatment.Under drought stress,compared with the control plants,the contents of electrolyte permeability,MDA and SS in Gh GGB silenced plants decreased,the contents of relative water content,Pro and H₂O₂increased,the activities of POD and CAT decreased,and the content of chlorophyll showed the same downward trend.Compared with the control plants,the relative water content and Pro content of Gh ROP8 silenced plants increased,while the MDA content decreased.These results indicated that Gh GGB and Gh ROP8 genes could participate in the regulation of drought resistance mechanism in cotton,and probably played a negative regulation role.5.Using cotton c DNA as a template,PCR cloned the Gh GGB gene,and constructed an overexpression vector of the gene,which was transformed into wild-type Arabidopsis thaliana by Agrobacterium,and a homozygous strain was obtained by screening.