USDA Plant Gene Expression Center
University of California
A gene required for floral and inflorescence meristem
--Laudencia-Chingcuanco, D; Hake, S
A recessive mutation, designated not under control (nuc), was
identified from our Ac/Ds field in the summer of 1995. nuc plants
are recognized in the field by the absence of protruding silks from
otherwise normal looking ears. De-husked ears reveal florets with
proliferous material at the center of the pistil. Upon closer
inspection, the mutation appears to disrupt a gene required for
the specification of a determinate floral meristem. In the female
flowers, the floral apex, which is normally consumed in the
formation of the gynoecium (see figure, wt) remains
indeterminate. After formation of the carpels, an unorganized
mass of pistillate tissue or an inflorescence-like, branching
meristem is produced at the center of the flower (figure, nuc).
The lower floret, which ultimately aborts, displays the same
phenotype as the upper floret. Pollinated nuc ears failed to
produce any kernels. In the tassel, additional male flowers form at
the position of the aborted pistil. Occasionally, a nucellar-like
mass is found at the center of these ectopic staminate flowers.
nuc inflorescences also have extra spikelets and florets. In the ear,
an extra spikelet forms between the spikelet pair. In the tassel,
up to 6 extra spikelet pairs are produced after the pedicellate
spikelet. Sometimes, an extra staminate flower is found between
the two flowers in the spikelet.
This transformation from flower to inflorescence shoot
meristem has also been reported to occur in several species under
particular growth conditions (Battey and Lyndon, Bot. Rev.
56:162, 1990; Okamura et al., PNAS 93:13831, 1996),
indicating that floral meristem determinacy is labile. Because nuc
is a single gene that is required to prevent indeterminacy within
the flower, we have a unique opportunity to explore the regulation
of determinacy in flowers.
Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors
Return to the MNL 71 On-Line Index
Return to the Maize Genome Database Page