Mechanism and biological function of the regulation of cellulose synthesis by light

纤维素是地球上含量最丰富的生物聚合物，在基础和应用植物研究中的研究越来越多，以促进未来的工业应用，如第二代生物燃料。在拟南芥中，初级纤维素是由六聚体纤维素合成酶复合体产生的，该复合体由纤维素合成酶(CESA)1、3和6组成，定位于质膜。CESA6的突变体在黑暗中表现出生长缺陷和纤维素缺乏，而在光照下的下胚轴中则没有。我们推测，这些表型在光中的拯救是光激活的CESA6相关亚型的存在的结果，该亚型可能是磷酸化的CESA5。本方案的实验目标是(1)通过共聚焦旋转圆盘显微镜分析CESA5的光调节、其在初级纤维素合成酶复合体中的存在、质膜运动和细胞内转运；(2)通过质谱仪和旋转圆盘显微镜分析CESA5的磷酸化状态和活性，将光激活CESA5与光敏色素诱导的磷酸化联系起来；以及(3)通过各种显微镜方法阐明CESA5在纤维素微纤维质量控制中的可能作用并确定其分子伙伴。

Cellulose is the most abundant biopolymer on earth and becomes increasingly studied in basic and applied plant research to promote future industrial applications such as second generation biofuels. In Arabidopsis, primary cellulose is produced by the hexameric cellulose synthase complex that is composed of the cellulose synthases (CESA) 1, 3 and 6 and localizes to the plasma membrane. Mutants in CESA6 show growth defects and cellulose deficiency in the dark-, but not in the light grown hypocotyl. We hypothesize that the rescue of these phenotypes in light is the result of the presence of a light-activated CESA6-related isoform, which might be phosphorylated CESA5. Experimental goals of the present proposal are (1) to analyze the regulation of CESA5 by light, its presence in the primary cellulose synthase complex, its plasma membrane motility and intracellular trafficking by confocal spinning disk microscopy, (2) to link the activation of CESA5 by light to phytochrome-induced phosphorylation by analyzing its phosphorylation state and activity by respectively mass spectrometry and spinning disk microscopy, and (3) to clarify the possible role of CESA5 in quality control of cellulose microfibrils by various microscopy methods and to identify its molecular partners.