About the Cover
Grass seed (technically referred to
as grain) are borne on axillary
branches whose branching patterns
dictate most of the variation
in grass inflorescence architecture.
Normal maize ears are unbranched,
and tassels have long
branches only at their base. The
ramosa2 (i>ra2) mutant of maize has
increased branching, with short
branches replaced by long, indeterminate
ones. Bortiri et al.
(pages 574-585) cloned ra2 and
report that it encodes a LOB
domain transcription factor. The
mutant phenotype and early expression
pattern of ra2 indicate
that it functions in the patterning
of stem cells in axillary meristems.
The ra2 expression pattern is
conserved in rice, barley, sorghum,
and maize, suggesting that
ra2 is critical for shaping the initial
steps of grass inflorescence architecture.
On the cover, a scanning
electron microscopy image
of a ra2 mutant ear (right) compared
to a normal ear (left) shows
the loss of determinacy and
branching in the ra2 mutant.
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Copyright © 2008 by the American Society of Plant Biologists
