Analysis Of Tobacco HD-ZIP Ⅳ Gene Family And Gene Function Of NtHD-ZIP Ⅳ-9 In Tobacco

Tobacco glandular hair is an important tissue on the surface of tobacco leaves.Secretions of glandular hair are the main components of leaf chemical substances and affect the quality and stress resistance of tobacco leaves.HD-ZIP Ⅳ family genes particIPate in the regulation of plant epidermal hair formation,epidermal cell differentiation,anthocyanin accumulation and root development,and play an important role in response to various abiotic stresses such as drought,salt and hormone.Based on bioinformatics analysis,HD-ZIP Ⅳ in the genome sequence of Nicotiana tobacum)K326 was widely predicted,and its full gene identification,full gene expression and other information research were carried out.These studies provide theoretical basis for in-depth analysis of tobacco HD-ZIP Ⅳ gene function.The main conclusions are as follows:1.There are 15 NtHD-ZIP Ⅳ gene members in common tobacco.Analysis of sequence characteristics of HD-ZIP Ⅳ gene showed that the length of amino acid encoded by HD-ZIP Ⅳ family genes varied from 359 to 828,the molecular weight of HD-ZIP Ⅳ protein was between 49.66 KDA and 91.77 KDA,and the isoelectric point was between 4.49 and 8.35 KDA.Cluster analysis of 74 HD-ZIP Ⅳ members from different plants showed that these proteins were divided into 5 groups.Tobacco HD-ZIP Ⅳmembers were closest to tomato and most distant to monocots rice.2.The expression pattern of NtHD-ZIP Ⅳ-1,-2,-3,-10 and-12 in stem epidermis was higher than that in skinless stem tissue,which may be related to the development of trichomes NtHD-ZIP Ⅳ-4,-5,-6,-13,and-14 have similar tissue expression patterns,which are not expressed in cotyledons but in leaf,root,stem epidermis and stem;NtHD-ZIP Ⅳ-8 is expressed only in cotyledons;NtHD-ZIP Ⅳ-15 is expressed only in root and epidermis;NtHD-ZIP Ⅳ-9 was expressed only in young leaves and Epidermis.Thus,each gene may be involved in the development of different plant organs.3.Abiotic stress and different plant hormone treatments showed that most NtHD-ZIP Ⅳ genes were induced by heat,cold,salt and drought.In addition,most of these genes were induced by GA,MeJA and SA,but inhibited by ABA.NtHD-ZIP Ⅳ gene was sensitive to heat,but not to osmotic stress.4.NtHD-ZIP Ⅳ-9 gene was cloned and its function was preliminarily identified.The results showed that the density of glandular hairs increased in the plants overexpressing ndhd-zip ⅳ-9,while the density of glandular hairs decreased significantly in the gene knockout lines,and the density of protective hairs increased significantly;The results of leaf secretion test also showed that the content of glandular hair secretion(cederane diterpenoids,sucrose esters and alkanes)in the overexpression lines was 50%higher than that in the control,while the content of glandular hair secretion in the knockout lines was significantly lower than that in the control.These results indicate that nthd zip ⅳ-9 gene can regulate the type of glandular hairs in tobacco.