The Roles of YUCCA Genes in Local Auxin Biosynthesis and Plant Development

Abstract

Auxin is an essential hormone for almost every aspect of plant growth and development. Much of the progress in understanding the roles of auxin in plant development is derived from findings in auxin signalling and polar auxin transport during the past two decades. However, recent molecular genetics studies in Arabidopsis have begun to reveal the secrets of auxin biosynthesis and its role in plant development. This chapter summarizes the recent progress in identifying YUCCA (YUC) flavin monooxygenases as key enzymes in auxin biosynthesis. Overexpression of YUC genes in Arabidopsis leads to auxin overproduction, and inactivation of YUC genes causes developmental defects that can be rescued by auxin produced in situ. The identification of YUC genes and loss-of-function yuc mutants provides a completely different angle for studying auxin biology because previous auxin studies were centred on understanding how plants respond to excess exogenous auxin. One example is provided on how understanding of auxin biosynthesis has helped to elucidate the mechanisms by which auxin regulates organogenesis in Arabidopsis.