YABBY Polarity Genes Mediate the Repression of KNOX Homeobox Genes in Arabidopsis

Abstract

The YABBY (YAB) genes specify abaxial cell fate in lateral organs in Arabidopsis. Loss-of-function mutants in two early-expressing YAB genes, FILAMENTOUS FLOWER (FIL) and YAB3, do not exhibit vegetative phenotypes as a result of redundancy. Mutations in these genes result in the derepression of the KNOX homeobox genes SHOOTMERISTEMLESS (STM), BREVIPEDICELLUS, and KNAT2 in the leaves and in the partial rescue of stm mutants. Here, we show that fil yab3 double mutants exhibit ectopic meristem formation on the adaxial surfaces of cotyledons and leaf blades. We propose that in addition to abaxial specification, lateral organ development requires YAB function to downregulate KNOTTED homeobox genes so that meristem initiation and growth are restricted to the apex.

Time to Stop: Flower Meristem Termination

“…Several members of the YABBY gene family exhibit complex interactions with meristematic genes including KNOX I genes, WUS and CLV3 (Sawa et al, 1999;Siegfried et al, 1999;Kumaran et al, 2002;Goldshmidt et al, 2008). However, whether similar interactions are responsible for CRC's function in FM termination remains unclear, as YAB2, which is not well characterized so far, is the only YABBY gene able to complement crc-1 (Meister et al, 2005;Fourquin et al, 2007).…”

Organ Polarity in Plants Is Specified through the Opposing Activity of Two Distinct Small Regulatory RNAs

“…The YABBY genes FILAMENTOUS FLOWER (FIL) and YAB3 act, at least in part, downstream of the HD-ZIPIII and KAN genes, whereas ARF3/ETT and ARF4 affect organ polarity through a distinct pathway (Sawa et al 1999;Siegfried et al 1999;Kumaran et al 2002;Pekker et al 2005). ARF3/ETT is expressed more broadly than ARF4, but both transcription factors colocalize in the abaxial domain of leaf primordia, where they act in combination with KAN proteins to promote abaxial fate (Pekker et al 2005).…”

AWUSCHEL-LIKE HOMEOBOXGene Represses aYABBYGene Expression Required for Rice Leaf Development

“…The myb transcription factor ASYMMETRIC LEAVES1 and ASYMMETRIC LEAVES2, a member of the LATERAL ORGAN BOUNDARIES family of transcriptional regulators, act together to repress expression of KNOX genes in the leaf (Byrne et al, 2000;Ori et al, 2000). Activity of the YABBY family of putative transcription factors also contributes to the exclusion of KNOX gene expression from Arabidopsis leaves (Kumaran et al, 2002).…”