Plant cell walls exhibit architectural and compositional changes throughout their development and in response to external cues. While tubulins (微管蛋白) are involved in cell wall biogenesis, much remains unknown about the scope of their involvement (参与) during the orchestration of this resource-demanding process. A transgenic approach coupled with cell wall compositional analysis, RNA-seq and mining of publicly available diurnal gene expression data was used to assess the involvement of tubulins in poplar leaf cell wall biogenesis. Leaf cell walls of transgenic poplar lines with constitutive overexpression of α-tubulin (TUA) exhibited an increased abundance of homogalacturonan (同型半乳糖醛酸聚糖), along with a reduction in xylose (戊醛糖). These changes were traced to altered expression of UDP-glucuronic acid decarboxylase (GADC; UDP-葡萄糖醛酸脱羧酶) in the transgenic leaves. A model is postulated by which altered diurnal control of TUA through its constitutive overexpression led to a metabolic tradeoff affecting cellular utilization of GADC substrate UDP-glucuronic acid. While there were no effects on cellulose, hemicellulose or lignin abundance, subtle (微妙的) effects on hemicellulose composition and associated gene expression were noted. In addition, expression and enzymatic activity of pectin methylesterase (PME; 果胶甲酯酶) decreased in the transgenic leaves. The change is discussed in a context of increased levels of PME substrate homogalacturonan, slow stomatal kinetics (气孔动力学) and the fate of PME product methanol (甲醇). Since stomatal opening and closing depend on fundamentally contrasting microtubule (微管) dynamics, the slowing of both processes in the transgenic lines as previously reported appears to be directly related to underlying cell wall compositional changes that were caused by tubulin manipulation.

Published data: September 12, 2017.