The CLAVATA3 (CLV3)-CLAVATA1 (CLV1) ligand-receptor kinase pair negatively regulates shoot stem

The CLAVATA3 (CLV3)-CLAVATA1 (CLV1) ligand-receptor kinase pair negatively regulates shoot stem cell proliferation in plants. expression in the RM partially complements the loss of regulation by CLV1 is distinct from CLV1 regulation of is expressed (Nimchuk et al. 2011 Rojo et al. 2002 There it promotes trafficking of CLV1 from CAL-101 (GS-1101) the plasma membrane to the lytic vacuole (Nimchuk et al. 2011 It is thought that CLV3 promotes CLV1 signaling which dampens stem RGS2 cell production by negatively regulating the expression of (expression forming a feedback loop that maintains a constant stem cell pool size (Brand et al. 2002 Yadav et al. 2013 Phenotypes for null mutations in and strong dominant-negative alleles of are roughly equivalent both causing increases in SAM size and stem cell number (Clark et al. 1993 1995 In floral meristems (FMs) these mutations result in increased numbers of floral organs allowing a quantitative measure of allele strength. By contrast CAL-101 (GS-1101) null mutants in show considerably weaker phenotypes than (Dievart et al. 2003 but the phenotype can be enhanced by mutations in the CLV1-related RKs ((DeYoung et al. 2006 DeYoung and Clark 2008 These results suggest that BAM1 and BAM2 act as redundant receptors for CLV3p. Consistent broad high-level expression of can complement null mutations (DeYoung et al. 2006 Triple mutants in and the related have the opposite effect on stem cell production displaying reductions in meristem size (DeYoung et al. 2006 Thus a complex set of interactions among related RKs controls stem cell production in the SAM. The molecular basis of these genetic interactions remains unknown. Transient transformation and overexpression studies in leaf tissue suggest that BAM1 and CLV1 receptors might interact; however it is not clear if this potential interaction is relevant in the cells of the SAM (Guo et al. 2010 Here we present a new model explaining the genetic redundancy among BAM RKs and CLV1. CLV1 functions exclusively in the RM and specifically represses gene transcription in response to CLV3p. Ectopic expression in the RM partially compensates for the loss of expression by CLV1 differs from the CLV1-dependent negative regulation of functions exclusively in functions in the SAM. Although CLV1 has been postulated to repress the transcription of functions outside of null plants with constructs expressing either wild-type promoter or a mutant of that is equivalent to the strong dominant-negative allele (Clark et al. 1993 Expression of was sufficient to fully complement the null mutant in the La-er background or the allele in a Col-0 background (Fig.?1) (Dievart et al. 2003 Kinoshita et al. 2010 By contrast plants displayed a phenotype similar to that of existing mutants complete with increased carpel production relative to the null as well as fasciation of the main stem and SAM (Fig.?1A B; data not shown). These data indicate that function in functions exclusively in (La-er) null mutant and expression compares to the expression of and in the SAM and FM. We focused on (DeYoung et al. 2006 generated native promoter binary vectors and used these to express a nuclear-targeted tandem Ypet fusion (2YN7). We transformed these binary vectors into wild-type plants to generate and transgenic reporter lines. Imaging by confocal microscopy determined that the patterns of expression of or reporters in roots were identical to those known from existing cell-specific transcriptomic profiling (Brady et al. 2007 indicating that our fluorescent reporter transgenes faithfully replicate cellular expression patterns (supplementary material Fig.?S1A B) (Depuydt et al. 2013 Consistent with this expression of a wild-type genomic coding sequence from the promoter complemented the phenotype (supplementary material Fig.?S1D). Furthermore expression of a mutant gene [dominant-negative CAL-101 (GS-1101) allele (Shinohara et al. 2012 that abolishes binding of the CLV3-related CLE9 peptide failed to restore rosette growth or fertility. Similarly complemented rosette size CAL-101 (GS-1101) and leaf shape (not shown). Previous work demonstrated that genomic expressed from the same promoter used in these studies complements the phenotype (Nimchuk et al. 2011 We examined expression of the and transcriptional reporters in the SAM (Fig.?2; supplementary material Fig.?S2). Consistent with previous accounts and our complementation data was highly expressed in the RM of the SAM (Clark et al. 1997 A minority of lines (2/20) showed weak expression in the L1 as also reported in a minority of lines in previous experiments (Nimchuk et al. 2011 In contrast to reporter was highly.