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 Experiment Station, Cornell University, Geneva, NY 14456-0462

ABSTRACT  The regulation of reproductive development in cauliflower (Brassica oleracea var. botrytis 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.

Full text at JXB Open Access

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