Identification and Functional Analysis of the Flower Development-Related TCP Genes in Erycina pusilla

Abstract

Orchid flowers have evolved in concert with pollinators to form highly specialized structures resulting in zygomorphy. In dicotyledons, it is widely accepted that CYC-like genes are involved in the dorsoventral polarity establishment of flowers, which determines the development of zygomorphic flowers. However, the function of TCP transcription factors involved in orchid floral development is rarely known. Here, we found 15 unigenes with TCP domain (EpTCPs) from the previously reported Erycina pusilla unigene database. The expression patterns of EpTCPs in various tissues and different floral organs were successively detected by quantitative real-time PCR. The results revealed that the CYC-like gene (EpTCP25) and CIN-like genes (EpTCP11 and EpTCP26) were highly expressed in inflorescences but lowly expressed in leaves and roots. What is more, these three genes were expressed relatively high in the dorsal labellum, and EpTCP26 showed differential expression along the dorsoventral polarity of tepals, which was high in the dorsal and low in the ventral. Ectopic expression of EpTCP25 in Arabidopsis repressed primary root growth and delayed flowering. EpTCP26 overexpression in Arabidopsis promoted primary root growth and leaf growth. In contrast, EpTCP11 overexpression repressed primary root growth and changed the radially symmetric flower to a bilaterally symmetric flower by inhibiting the elongation of one or two adjacent petals. In addition, the homeotic transition of floral organs is generated when these genes are ectopically expressed in Arabidopsis, suggesting their roles in floral morphogenesis. Altogether, our results indicate that CIN-like genes would be associated with the unique flower pattern development of Erycina pusilla.