Functional Characterizations Of Poplar MSBP1 In Lignin Biosynthesis

Poplar,as a model species for tree research,poplar is established a perfect genetic transformation system.There is of great significance to reduce paper-making costs and produce biomass energy via cultivating genetically modified wood species with excellent wood properties,regulating the lignin and improving wood quality.Membrane steroid-binding protein(MSBP)is a type of scaffold protein anchored on the plasma,which affects multiple processes of plant growth and development by initiating cell response and regulating steroid transport and metabolism.This study aims to explore the function of poplar MSBP gene in the wood formation processes and give insight into the improvement of wood quality.The results are as follows:There 7 MSBP members are obtained through aligning Arabidopsis thaliana MSBP1(AtMSBP1)gene sequence with 84 K poplar(Populus alba × P.glandulosa)genome.All 7 PagMSBP members are structurally conservative,with a Cyt-b5 domain.Among them,PagMSBP1/2a the highest amino acid identity AtMSBP1.Analysis of promoter cis-acting elements showed that the promoter region of PagMSBPs contains more light-and hormone-responsive elements.84 K poplar was used as the research subject to analysis the relative expression level of the MSBP gene in different tissues.The results showed that the expression level of PagMSBP1/2a in the old stems with high lignification was significantly higher than that in the young stems;which is highly consistent with the result that PtMSBP1/2a highly expression in the xylem shown as Aspwood database.In order to explore the biochemical characteristics and function prediction,PagMSBP1/2a was cloned from 84 K poplar.The analysis of PagMSBP1/2a protein sequence showed that its N-terminal contains a transmembrane domain and PagMSBP1/2a is located in the endoplasmic reticulum by subcellular localization analysis.In addition,PagMSBP1/2a showed a response to salt stress under abiotic stress treatment.PagMSBP1/2a overexpression transgenic poplars were obtained by Agrobacterium-mediated leaf disc method for studying its genetic function.Phenotypic observation showed that the transgenic poplars grew slower and their plant height was shorter than contorol.The lignin content of stems of PagMSBP1/2a overexpression poplar was significantly lower than that of control poplar,with up to 34.6%.The activity of P450 enzyme C4 H was also significantly lower in the overexpression plants.Based on the above research results,PagMSBP1/2a,as a scaffold protein located in the endoplasmic reticulum,is involved in the regulation of lignin biosynthesis during the poplar wood formation.