Abstract
Differentiating xylem vessels develop secondary cell walls in distinct patterns following dramatic re-arrangement of cortical microtubules. Because xylem cells are formed in the center of plant organs, analysis of cellular events in xylem cells, in particular, in living xylem cells, has long been difficult. Recently, we established an in vitro Arabidopsis cell culture system, in which estrogen-induced expression of a xylem master transcription factor triggers xylem differentiation. This system enabled us to analyze the molecular dynamics during xylem differentiation. Using this system, we performed various lines of analysis such as microarray analysis, high-throughput live imaging, in vivo detection of protein-protein interaction, and functional analysis of novel genes. These analyses revealed that a ROP GTPase and MIDD1, which is a novel microtubule-associated protein, are essential components of secondary wall patterning. In this review, we summarize recent knowledge of molecular components governing secondary wall patterning, with emphasizing MIDD1 and a ROP GTPase.
