Maize Genetics Cooperation Newsletter

maize gene review

Authors: Erik Vollbrecht1 and Sarah Hake2
1Iowa State University, Ames, IA 50011 USA; 2 USDA ARS, Albany, CA 40179 USA


Review: pending

Pub date: Mar 2009

Name: ra2 ramosa2

Chromosome 3S bin 3.03
Genome Browser via BAC c0064i05 sequence AC191912

Function: infloresence architecture, a LOB-domain putative transcription factor

image of corn mutant

Summary: The ramosa2 mutant is visible in the ear and tassel. Mutant tassels do not have a sharp distinction between branches and spikelet pairs; rather, the long branches become shorter gradually toward the tip. Secondary branching occurs at a higher frequency. Often there are branches with spikelet pairs and single spikelets intermixed. Spikelet pair and spikelet pedicels are elongated, again becoming gradually less so toward the tip. In the ear, kernel rows may be uneven and branches may form, depending on allele and background. The phenotype is similar to ra1 and ra3, except ra2 mutants also have upright tassel branches. Expression levels of ra1 are decreased in ra2 mutants (Vollbrecht et al. 2005; Bortiri et al. 2006). The ra2 gene encodes a LOB (Lateral Organ Boundary) domain protein that is expressed transiently in branch meristems, spikelet pair meristems and spikelet meristems. A similar expression pattern is seen in other cereal species (Bortiri et al. 2006).

Image: ra2 ear and tassel

First and defining reports:  Emerson et al. 1935, citing Brink. Bortiri et al 2006

Key Alleles

ra2-mum4 ARG to HIS.

ra2-DM deletion of LOB domain, leaving a C terminal conserved domain intact.

ra2-ref 8 bp insertion that introduces a stop codon in LOB domain.


Bortiri, E., Chuck, G., Vollbrecht, E., Rocheford, T.F., Martienssen, R., and Hake, S. (2006). ramosa2 encodes a Lateral Organ Boundary domain protein that determines the fate of stem cells in branch meristems of maize. The Plant Cell 18: 574-585. PUBMED

Emerson RA, Beadle GW, and Fraser AC (1935). A summary of linkage studies in maize. Cornell Univ. Agric. Exp. Sta. Mem. 180: 1-83.

Vollbrecht E, Springer PS, Goh L., Buckler ES and Martienssen R. (2005). Architecture of floral branch systems in maize and related grasses. Nature 436:1119-1126. PUBMED

Links: ra2 NCBI ra2 UniProt Q27YF3