The role of cortical microtubules in wood formation

Abstract

ABSTRACT During differentiation of cambial cells into secondary xylem cells in trees (wood formation), newly deposited cellulose microfibrils on the innermost surface of cell walls change their orientation progressively. The orientation of cellulose microfibrils in the secondary wall, referred to as the microfibril angle, is one of the most important characteristics that determine the properties of wood. In particular, the angle in the thickest middle layer (S 2 layer) of secondary wall is closely related to mechanical properties. Therefore, the control of orientation of cellulose microfibrils allows us to change the quality of wood and its products. Recent observations in a wide variety of trees have revealed that there is a close relationship between the orientation of cortical microtubules, which are one component of cytoskeleton, and the orientation of newly deposited cellulose microfibrils in differentiating secondary xylem cells. Such a close relationship has been found in both normal, compression wood and tension wood. These evidences indicate that cortical microtubules play an important role in the control of the orientation of cellulose microfibrils in secondary xylem cells. Therefore, biotechnological control of the orientation of cellulose microfibrils in the cell walls by manipulation of cortical microtubules provides new tools to improve the quality of wood and its products.