title: STENOFOLIA recruits TOPLESS to repress ASYMMETRIC LEAVES2 at the leaf margin and promote leaf blade outgrowth in Medicago truncatula.
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.
authors.affiliation: Department of Plant and Soil Sciences, Institute for Agricultural Biosciences, Oklahoma State University, Ardmore, Oklahoma 73401.
authors.forename: Fei
authors.initials: F
authors.lastname: Zhang
authors.forename: Yewei
authors.initials: Y
authors.lastname: Wang
authors.forename: Guifen
authors.initials: G
authors.lastname: Li
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Tang
authors.forename: Elena M
authors.initials: EM
authors.lastname: Kramer
authors.forename: Million
authors.initials: M
authors.lastname: Tadege
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D020868:Gene Silencing; D046913:Medicago truncatula / Q000254:growth & development* / Q000378:metabolism*; D008969:Molecular Sequence Data; D010641:Phenotype; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000254:growth & development*; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014026:Nicotiana / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D012097:Repressor Proteins