第1214回生物科学セミナー

Identification of MYB transcription factors controlling secondary cell wall deposition in poplar wood fibers

Dr. Annabelle Déjardin(BioForA, INRA)

2018年06月11日(Mon)    16:00-17:00  理学部2号館 講堂   

The deposition of secondary cell wall in wood fibers is a complex process that requires the coordinated expression of a high number of genes. Plant R2R3-MYB transcription factors are known to play an important role in plant secondary cell wall formation, by activating or repressing their target genes in a coordinated manner within a complex regulatory network. They belong to a large gene family - 180 genes in poplar -, with some members already identified as master switches in the regulation network (Zhang et al, 2014). Here, we combined genetic engineering and chromatin immuno-precipitation technique (ChIP-SEQ) in order to elucidate the function of two R2R3-MYB transcription factors in poplar, MYB090 and MYB156. MYB090 potentially regulates a high number of target genes in planta through a highly conserved motif, similar to GAMYB. These target genes are involved in the biosynthetic pathways of lignin, cellulose and xylans, which are the major components of secondary cell walls. Overexpression of MYB090 in poplar reduced stem growth and its total lignin content; lignification was severely impacted in wood parenchyma rays. By contrast, overexpression of MYB156 in poplar showed no apparent growth defect, while the total lignin content was decreased by 15% in the stem. These plants exhibited hypolignified fibers while the lignification of vessels seemed unaffected.
These different results led to the conclusion that both MYB factors are transcriptional repressors of lignification, but act at different levels of the regulatory network. This work opens new avenues on the building of transcriptional regulatory networks involved in secondary cell wall formation. It also generated new poplar transgenic lines with desired traits for bioethanol production.