Interactions between WUSCHEL- and CYC2-like Transcription Factors in Regulating the Development of Reproductive Organs in Chrysanthemum morifolium

Abstract

<i>Chrysanthemum morifolium</i> is a gynomonoecious plant that bears both female zygomorphic ray florets and bisexual actinomorphic disc florets in the inflorescence. This sexual system is quite prevalent in Asteraceae, but poorly understood. CYCLOIDEA (CYC) 2 subclade transcription factors, key regulators of flower symmetry and floret identity in Asteraceae, have also been speculated to function in reproductive organs and could be an entry point for studying gynomonoecy. However, the molecular mechanism is still unclear. On the other hand, the <i>Arabidopsis</i> WUSCHEL (WUS) transcription factor has been proven to play a vital role in the development of reproductive organs. Here, a <i>WUS</i> homologue (<i>CmWUS</i>) in <i>C. morifolium</i> was isolated and characterized. Overexpression of <i>CmWUS</i> in <i>A. thaliana</i> led to shorter siliques and fewer stamens, which was similar to <i>CYC2</i>-like genes reported before. In addition, both <i>CmWUS</i> and <i>CmCYC2</i> were highly expressed in flower buds during floral organ differentiation and in the reproductive organs at later development stages, indicating their involvement in the development of reproductive organs. Moreover, CmWUS could directly interact with CmCYC2d. Thus, our data suggest a collaboration between CmWUS and CmCYC2 in the regulation of reproductive organ development in chrysanthemum and will contribute to a further understanding of the gynomonoecious sexual system in Asteraceae.