Cloning And Expression Analysis Of Genes Related To Screening And Defoliation Response Of Cotton For TDZ Sensitive Materials

Sensitivity to defoliants is an important feature of machine picking cotton.TDZ treatment is used to screen materials sensitive to defoliants,and related mechanisms are studied.Cloning cotton defoliation responds to related genes and analyzes expression characteristics.It has a certain theoretical significance for cultivating machine picking cotton varieties.In this study,55 cotton materials were used as experimental materials,and defoliants were treated in two periods in the pre-blow-out period.The sensitivity of defoliants to 55 cotton materials was evaluated comprehensively by means of variance analysis,and physiological indicators were found that were closely related to TDZ sensitivity.Selection of cotton materials sensitive to defoliants.Based on the previous research on the genes related to organ exfoliation,it is found that the GH9 gene family in glycoside hydrolase plays an important role in organ exfoliation,fruit maturity,and cellulose biosynthesis and modification.The mRNA sequence of the Arabidopsis EG 17 gene（Sequence ID:NC 003070.9）and the tomato Tapg2 gene（Sequence ID:NC₀15439）published on the NCBI website is used as a reference sequence to screen out two cotton related genes that fall off.The total length of the cDNA of these two genes was obtained by homologous cloning and named GhEG17 and Gh Tapg2.Their structure and function were predicted and analyzed using related bioinformatics software.QRT-PCR technology was used to detect the expression of these two genes in different parts,different treatments and different periods under TDZ treatment.The results are as follows:1.The method of variance analysis was used to screen 55 cotton materials for defoliant sensitivity.The sensitive materials based on the results of the defoliation index are mainly medium cotton 35,19 sun 1u zao and 50 sun 1u zao,and the insensitive materials are mainly Nong Da 5 and XND1378;There are tissue differences in the activity of cellulase and polygalactoalase（PG）:Yeto and GT;Petiole=leaf blade;PG activity was significantly higher than CK（P<UNK>0.05）in the five periods of 6h,18h,42h,66h,and 96h;Cellulase activity was significantly higher than CK（P<UNK>0.05）in the three periods of 6h,66h,and 96h,and significantly higher than CK（P<UNK>0.01）in the two periods of 18h and 42h.Based on the results of physiological indicators,sensitive materials mainly include medium cotton 35 and 50 sun lu zao.According to the evaluation results of the two traits,the 50 sun lu zao was selected as the follow-up test material.2.Using homologous cloning methods to clone GhEG17 and GhTapg2 genes,and using software to carry out bioinformatics analysis of these two genes,the results show that the open reading frames of GhEG17 and GhTapg2 genes are 1533bp and 1176bp,respectively,encoding 510 amino acids and 391 amino acids.The predicted protein molecular weight of the two genes was approximately 56.89 kD and 41.56kD,respectively;The isoelectric points are 9.48 and 9.06.It is found that there is a conserved homologous heterotype domain in the GhEG17 and GHTapg2 sequences.The results of GhEG17 genetic system evolution tree analysis show that GhEGl7 and GaEG17 are clustered in the same small branch,and EG 17 is clustered in another small branch,indicating that the EG 17 gene in terrestrial cotton is closely related to the same gene in Asian cotton.The results of the evolutionary tree analysis of the GhTapg2 gene system showed that the GhTapg2 protein of terrestrial cotton was distributed on the same branch as that of Raymond’s cotton Gritapg2 protein,indicating that the two were closely related to each other in evolution.3.QRT-PCR results showed that GhEG17 and GhTapg2 genes were expressed in different degrees under the action of defoliants.In cotton,GhEG17 and Yetuo 2 had histspecific expression in Yetuo,petiole,and leaf blade,but the expression pattern was specific in Yetuo.The GhEG17 and genes in cotton had the highest expression in the 18 H tissue of 50 sun lu zao.