Defense Date


Document Type


Degree Name

Master of Science



First Advisor

Wenheng Zhang, Ph.D


CYCLOIDEA (CYC) and DICHOTOMA (DICH) of the CYC2 clade of the TCP gene family have been shown to play a significant role in regulating the identity of the dorsal petals and abortion of the single dorsal stamen in Antirrhinum majus. It is believed that CYC2-like genes are responsible for the convergent evolution of floral zygomorphy, but their role in the development of actinomorphic flowers is still unknown. In Solanaceae, previous analysis has identified two paralogs of CYC2-like genes, CYC2A and CYC2B, resulting from a gene duplication that predates the origin the family. Virus-induced gene silencing (VIGS) is a technique to study the gene function by silencing specific target genes of interest, which is shown to be useful in diverse plant species. Here, we report on the role of CYC2-like genes during floral development in Solanaceae based on the results of VIGS using tobacco rattle virus (TRV)-based vector in Solanum lycopersicum having completely actinomorphic flowers and Nicotiana obtusifolia having slightly zygomorphic flowers. Our VIGS experiments in So. lycopersicum show that downregulation of both CYC2A and CYC2B leads to misshaped petals, the unequal growth of the petals, and most frequently increased number of petals, stamens and sepals, while the carpel and ovule morphology remain the same as the wild type. On the contrary, downregulation of CYC2A and CYC2B in N. obtusifolia results in reduced number of flower organs in sepals, stamens, and petals, however carpels remained the same. For both solanaceous species, silencing CYC2A and CYC2B changes the property of cytoplasm and retards the rate of pollen germination. Our findings suggest that the CYC2-like genes are likely involved in the floral development, mainly regulating the number of floral organs and pollen development in Solanaceae.


© Joonseog Kim, 2017

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