Multi-level analysis of the interactions between REVOLUTA and MORE AXILLARY BRANCHES 2 in controlling plant development reveals parallel, independent and antagonistic functions

Class III homeodomain leucine zipper (HD-ZIPIII) transcription factors play fundamental roles in controlling plant development. The known HD-ZIPIII target genes encode proteins involved in the production and dissipation of the auxin signal, HD-ZIPII transcription factors and components that feedback-regulate HD-ZIPIII expression or protein activity. Here we investigated the regulatory hierarchies of the control of MORE AXILLARY BRANCHES2 (MAX2) by the HD-ZIPIII protein REVOLUTA (REV). We found that REV can interact with the promoter of MAX2 In agreement had rev10D, gain-of-function mutants increased levels of MAX2 expression while rev loss-of-function mutants showed lower levels of MAX2 in some tissues. Like REV, plays MAX2 known roles in the control of plant architecture, photobiology and senescence which prompted us to initiate a multi-level analysis of growth phenotypes of hd-zipIII, max2 and respective higher order mutants thereof. Our data suggest a complex relationship of synergistic and antagonistic activities between REV and MAX2 and these interactions appear to depend on the developmental context and not all involve the direct regulation of MAX2 by REV.