Journal of Experimental
Botany 59(2):421-433; doi:10.1093/jxb/erm327
Meristem Gene Expression During Reproductive Development in Brassica oleracea
Denise V. Duclos and Thomas Björkman
Department of Horticultural Sciences, New York State Agricultural
Station, Cornell University, Geneva, NY 14456-0462
ABSTRACT The regulation of reproductive
development in cauliflower (Brassica
DC) and broccoli (B.
oleracea L. var. italica
Plenck) is unusual in that most enlargement occurs while development is
arrested at a distinct stage. Cauliflower and broccoli curds are
composed by inflorescence meristems and flower buds, respectively. To
determine whether this arrest is maintained by altered expression of
the genes that specify these steps in Arabidopsis, the
expression of each copy of their homologs (MADS-box genes BoAP1-a, BoAP1-c, BoCAL, BoFUL-a, BoFUL-b, BoFUL-c, BoFUL-d; and
non-MADS-box genes BoLFY,
AP2, UFO, BoTFL1, CCE1, and BoREM1) was
measured simultaneously in heads that were arrested at different
developmental stages by varying temperature, but had a common genotype.
Transcript abundance of BoFUL
paralogs and BoLFY
was highest at the cauliflower stage of arrest, consistent with these
genes initiating inflorescence meristems. The expression of other genes
was the same regardless of the developmental stage of arrest. We can
therefore exclude the expected models, wherein maintenance of arrest at
the inflorescence meristem is a consequence of suppression of BoCAL, BoAP1-a or BoLFY, or failure
to suppress BoTFL1.
Floral primordia and floral buds were normal in boap1-a boap1-c bocal
triple mutants; therefore, other meristem identity genes can specify
floral initiation (A-function) in B. oleracea. BoTFL1, a strong
repressor of flowering in Arabidopsis,
did not suppress the formation of the floral primordium in B. oleracea.
Initiation of floral primordia and enlargement of floral buds in
broccoli and cauliflower is not controlled solely by homologs of the
genes that do so in Arabidopsis.
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