Abstract
During xylem vessel formation it is known that various events, such as secondary wall thickenings and programmed cell death, occur synchronously. We have identified many genes involved in these events by using microarray analyses during in vitro vessel element formation. However, little is known about the regulatory mechanisms underlying the synchronous expression of these genes. In this study, the FOX-hunting system was used to screen for regulatory factors of xylem vessel formation, which may regulate the expression of xylem vessel marker genes, PaspA3 and Atxyn3 encoding an aspartic proteinase and a xylanase, respectively, based on these promoter activity. As a result, we identified a mutant showing the ectopic activity of PaspA3 promoter but not showing that of Atxyn3 promoter. We also found that the overexpression of a bHLH gene caused the mutant phenotype. Now we are analyzing intrinsic functions of the bHLH and other bHLH included in the same subfamily.
