Arabidopsis REGULATOR OF AXILLARY MERISTEMS1 controls a leaf axil stem cell niche and modulates vegetative development.
Shoot branching is a major determinant of variation in plant stature. Branches, which form secondary growth axes, originate from stem cells activated in leaf axils. The initial steps by which axillary meristems (AMs) are specified and their stem cells organized are still poorly understood. We identified gain- and loss-of-function alleles at the Arabidopsis thaliana REGULATOR OF AXILLARY MERISTEMS1 (RAX1) locus. RAX1 is encoded by the Myb-like transcription factor MYB37 and is an Arabidopsis homolog of the tomato (Solanum lycopersicum) Blind gene. RAX1 is transiently expressed in a small central domain within the boundary zone separating shoot apical meristem and leaf primordia early in leaf primordium development. RAX1 genetically interacts with CUP-SHAPED COTYLEDON (CUC) genes and is required for the expression of CUC2 in the RAX1 expression domain, suggesting that RAX1 acts through CUC2. We propose that RAX1 functions to positionally specify a stem cell niche for AM formation. RAX1 also affects the timing of developmental phase transitions by negatively regulating gibberellic acid levels in the shoot apex. RAX1 thus defines a novel activity that links the specification of AM formation with the modulation of the rate of progression through developmental phases.
Institute of Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR, Scotland, United Kingdom.
Thomas
T
Keller
Jessica
J
Abbott
Thomas
T
Moritz
Peter
P
Doerner
D000483:Alleles; D017360:Arabidopsis / Q000033:anatomy & histology / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015415:Biomarkers / Q000378:metabolism; D018628:Gene Dosage; D018506:Gene Expression Regulation, Plant; D005875:Gibberellins / Q000378:metabolism; D018519:Meristem / Q000378:metabolism / Q000648:ultrastructure; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013234:Stem Cells / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015533:Transcriptional Activation / Q000235:genetics
D029681:Arabidopsis Proteins; D015415:Biomarkers; C107294:CUC2 protein, Arabidopsis; D005875:Gibberellins; D020598:Proto-Oncogene Proteins c-myb; C510420:RAX1 protein, Arabidopsis; D014157:Transcription Factors; C007842:gibberellic acid