STENOFOLIA recruits TOPLESS to repress ASYMMETRIC LEAVES2 at the leaf margin and promote leaf blade outgrowth in Medicago truncatula

Date Published:

Feb

Abstract:

The Medicago truncatula WUSCHEL-related homeobox (WOX) gene, STENOFOLIA (STF), plays a key role in leaf blade outgrowth by promoting cell proliferation at the adaxial-abaxial junction. STF functions primarily as a transcriptional repressor, but the underlying molecular mechanism is unknown. Here, we report the identification of a protein interaction partner and a direct target, shedding light on the mechanism of STF function. Two highly conserved motifs in the C-terminal domain of STF, the WUSCHEL (WUS) box and the STF box, cooperatively recruit TOPLESS (Mt-TPL) family corepressors, and this recruitment is required for STF function, as deletion of these two domains (STFdel) impaired blade outgrowth whereas fusing Mt-TPL to STFdel restored function. The homeodomain motif is required for direct repression of ASYMMETRIC LEAVES2 (Mt-AS2), silencing of which partially rescues the stf mutant phenotype. STF and LAMINALESS1 (LAM1) are functional orthologs. A single amino acid (Asn to Ile) substitution in the homeodomain abolished the repression of Mt-AS2 and STF's ability to complement the lam1 mutant of Nicotiana sylvestris. Our data together support a model in which STF recruits corepressors to transcriptionally repress its targets during leaf blade morphogenesis. We propose that recruitment of TPL/TPL-related proteins may be a common mechanism in the repressive function of modern/WUS clade WOX genes.

Notes:

Zhang, FeiWang, YeweiLi, GuifenTang, YuhongKramer, Elena MTadege, MillionengResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.2014/03/04 06:00Plant Cell. 2014 Feb;26(2):650-64. doi: 10.1105/tpc.113.121947. Epub 2014 Feb 28.

Last updated on 05/22/2015