Abstract
The biosynthesis of cellulose,lignin,and hemi-celluloses in plant secondary cell walls(SCWs)is regulated by a hierarchical transcriptional regulatory network.This network features or-thologous transcription factors shared between poplar and Arabidopsis,highlighting a founda-tional similarity in their genetic regulation.However,knowledge on the discrepant behavior of the transcriptional-level molecular regulatory mechanisms between poplar and Arabidopsis remains limited.In this study,we investigated the function of PagMYB128 during wood for-mation and found it had broader impacts on SCW formation compared to its Arabidopsis ortholog,AtMYB103.Transgenic poplar trees overexpressing PagMYB128 exhibited sig-nificantly enhanced xylem development,with fiber cells and vessels displaying thicker walls,and an increase in the levels of cellulose,lignin,and hemicelluloses in the wood.In contrast,plants with dominant repression of PagMYB128 demonstrated the opposite phenotypes.RNA sequencing and reverse transcription-quantitative polymerase chain reaction showed that PagMYB1 28 could ac-tivate SCW biosynthetic gene expression,and chromatin immunoprecipitation along with yeast one-hybrid,and effector-reporter assays showed this regulation was direct.Further analysis revealed that PagSND1(SECONDARY WALL-ASSOCIATED NAC-DOMAIN PROTEIN1)directly regulates PagMYB128 but not cell wall metabolic genes,highlighting the pivotal role of PagMYB1 28 in the SND1-driven regulatory network for wood devel-opment,thereby creating a feedforward loop in SCW biosynthesis.
维普
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