Requirement of Homeobox Gene STIMPY/WOX9 for Arabidopsis Meristem Growth and Maintenance

Abstract

Most organs of flowering plants develop postembryonically from groups of pluripotent cells called meristems [1]. The shoot apical meristem (SAM) is specified by two complementary pathways [2-4]. SHOOT MERISTEMLESS (STM; [5]) defines the entire SAM region [6]. WUSCHEL (WUS), on the other hand, functions in a more restricted set of cells to promote stem-cell fate and is regulated by the CLAVATA genes in a negative feedback loop [7-10]. In contrast, little is known about how the growth of the SAM, which increases in size during vegetative development [11], is regulated. We have characterized STIMPY (STIP; also called WOX9 [12]), a homeobox gene required for the growth of the vegetative SAM, in part by positively regulating WUS expression. In addition, STIP is required in several other aerial organs and the root. What sets STIP apart from STM and WUS is that stip mutants can be fully rescued by stimulating the entry into the cell cycle with sucrose. Therefore, STIP is likely to act in all these tissues by maintaining cell division and preventing premature differentiation. Taken together, our findings suggest that STIP identifies a new genetic pathway integrating developmental signals with cell-cycle control.

Evolutionarily conserved repressive activity of WOX proteins mediates leaf blade outgrowth and floral organ development in plants

“…WOX9 has been proposed to coordinate cytokinin-and sugar-mediated signaling in shoot meristem development (27)(28)(29). In addition, STF modulation of robust hormone and sugar homeostasis in leaf blade development has been proposed (15).…”

WOX13-like genes are required for reprogramming of leaf and protoplast cells into stem cells in the moss Physcomitrella patens

“…In addition, WUS and WOX5 are involved in the de novo formation of meristems and somatic embryos from differentiated cells (Zuo et al, 2002;Gallois et al, 2004;Gordon et al, 2007;Chen et al, 2009;Sugimoto et al, 2010). Second, two members of the WOX9 clade, WOX8 and WOX9, redundantly regulate zygote development and embryo axis formation (Breuninger et al, 2008;Ueda et al, 2011) and WOX9 has an additional role in shoot meristem regulation (Wu et al, 2005). Finally, recent reports show that members of the WOX13 clade affect replum development, and dehiscence, flowering time, lateral root formation, and fertility (Deveaux et al, 2008;Romera-Branchat et al, 2012).…”

Rice WUSCHEL-related homeobox 3A (OsWOX3A) modulates auxin-transport gene expression in lateral root and root hair development

“…4 WOX5 functions in stem cell maintenance 5 and WOX9/ STIMPY acts in early embryonic growth in the root apices. 6 In rice, WOX11 plays an important role in the emergence and growth of adventitious roots, and directly represses the cytokinin type-A responsive regulator RR2, which is expressed in adventitious root primordia. 7 Our recent study demonstrated that OsWOX3A regulates the development of lateral roots, but not adventitious roots.…”