Function Analysis Of PtrMYB42-like Gene In Cell Wall Formation Of Populus Trichocarpa

Poplar,as a model plant,is an important economic tree.Poplar’s wood is widely used in the production and living.Wood is primarily composed of secondary xylem,and the main structural components of the secondary xylem are lignin and cellulose.Based on the different angles of cellulose micro fiber,the secondary cell wall is divided into three layers,S1,S2 and S3.Sometimes,adjacent to the inner layer,there is another layer,called G layer.The mature secondary xylem is mainly composed of xylem parenchyma cells,lignified fibers,vessels,and tubular molecules.The MYB transcription factor family has many members.The members are involved in multiple biological processes,including transmission of hormone signals,resistance to pathogen invasion,development of xylem,and synthesis of lignin.Meanwhile,it participates in the regulation of plant physiological metabolism and responses to abiotic stresses,such as drought and salt.In order to predict the function of transcription factor PtrMYB42-like,its protein structure was analyzed using bioinformatics software and online program.PtrMYB42-like belongs to the R2R3-MYB subfamily.A total of 197 R2R3-MYB subfamily members were identified in Populus trichocarpa and divided into 42 subgroups.The protein encoded by PtrMYB42-like was localized in the nucleus,suggesting that it functions in the nucleus.The expression pattern of PtrMYB42-like gene in different tissues was analyzed using transcriptome data and q RTPCR.The results showed that PtrMYB42-like was exclusively expressed in xylem and highly expressed when secondary cell wall was thickened,suggesting its role in the development of wood fibers.To investigate the function of PtrMYB42-like in cell wall development,a plant expression vector,p CAMBIA1300-PtrMYB42-like,was constructed,genetic transformation of Populus trichocarpa was carried out,and finally the transgenic plants overexpressing PtrMYB42-like were obtained.The phenotype and growth parameters of the transgenic plants were measured.No obvious differences were observed between the transgenic and wild type plants.Toluidine blue staining and scanning electron microscope(SEM)images showed that,in the stems of transgenic plants,the amount of G fibers in the secondary xylem was increased,while the thickness of S layer was thinned and the diameter of vessels was decreased compared with those in the wild type plants.These results indicated that PtrMYB42-like is involved in the secondary growth of stems,and overexpression of PtrMYB42-like improved the synthesis of G layer in the secondary xylem fiber cells of Populus trichocarpa.