GREEN TISSUE-SPECIFIC PROMOTERS USED TO ALTER LIGNIN PRODUCTION IN SWITCHGRASS
Genetic engineering of switchgrass (Panicum virgatum L.) for reduced cell wall recalcitrance and improved biofuel production has long been a goal. Promoters have been used to control the expression of cell wall synthesis genes toward the goal. However, these often lead to undesirable plant phenotypic effects. Green tissue-specific promoters from switchgrass are potentially valuable to alter cell wall traits while not changing phenotypes.
The team of Wusheng Liu, Mitra Mazarei, and Rongjian Ye from the University of Tennessee in the USA studied three switchgrass green tissue-specific promoters in rice. They then used them to direct the expression of the switchgrass PvMYB4 transcription factor gene in transgenic switchgrass to confer reduced recalcitrance in aboveground biomass.
Analysis detected the strong expression of the PvMYB4 in the aboveground tissues, including leaf blades, leaf sheaths, internodes, inflorescences, and nodes of switchgrass. The green tissue-specific expression of PvMYB4 in transgenic switchgrass led to significant gains in saccharification efficiency and decreased levels of lignin. Furthermore, plant growth was not compromised in green tissue-expressed PvMYB4 switchgrass plants.
This study suggests that green tissue-specific expression of PvMYB4 is an effective strategy for the improvement of transgenic feedstocks.