Temporal–spatial patterns of ABCDE model genes expressed in new flowers that emerge from the centres of existing flowers in Chinese cabbage

We examined the formation of flower buds and floral organs at five growth stages and compared between normal flowers and those that emerged from the centre of another flower (i.e. flowers-in-flower). Gene expression was analysed via qRT-PCR. When compared with normal flowers, expression of nine genes at corresponding time periods showed clearly different trends in the flowers-in-flower samples, depending upon whether those abnormal structures were of the first types (1-1 and 1-2) or the second types (2-1 and 2-2). For example, at each time point, expression of AP2, STK and SHP was notably higher in 2-1 flowers than in either 1-1 or 1-2 flowers. By contrast, AG expression was up-regulated more between Stages 4 and 5 for normal flowers than for the other types. Furthermore, when compared with normal floral organs, AP1 transcripts were barely detected in the stamens and pistils of mutant samples, and expression was lower in the flowers-in-flower sepals and petals. Except for 2-2 flowers at Stage 5, STK and SHP expression was higher in the mutant organs than in the normal organs. These results suggest that formation of the flowers-in-flower morphology is closely related to down-regulation of AP1 and AG and up-regulation of AP2, STK, and SHP.