Heterologous expression of chrysanthemum TOPLESS corepressor CmTPL1-1 alters meristem maintenance and organ development in Arabidopsis thaliana.

TOPLESS (TPL)/TOPLESS-related (TPR) corepressors are important regulators of plant growth and development, but their functions in chrysanthemum (Chrysanthemum morifolium) are currently unclear. In this study, a chrysanthemum TPL/TPR family gene, designated CmTPL1-1, was characterized. This gene encodes an 1135-amino-acid polypeptide harboring a conserved N-terminal domain and two C-terminal WD40 domains. CmTPL1-1 showed no transcriptional activity in yeast, and a localization experiment indicated that it localized to the nuclei in onion epidermal cells. Transcript profiling established that the gene was most highly expressed in the stem apex. The heterologous expression of CmTPL1-1 in Arabidopsis thaliana produced a pleiotropic phenotype, including smaller leaves, shorter siliques, increased meristem number, asymmetrical petal distribution and reduced stamen number. In transgenic plants, four AtARFs were downregulated, while six AtIAAs and two AtGH3s were upregulated at the transcript level; moreover, the expression of three key class I KNOTTED-like homeobox (KNOX) genes was upregulated. In addition, by yeast two-hybrid screening of a chrysanthemum cDNA library, we found that CmTPL1-1 could interact with CmWOX4, CmLBD38 and CmLBD36, and these interactions were confirmed by bimolecular fluorescence complementation (BiFC) assays. Overall, we speculated that heterologous expression of CmTPL1-1 regulates plant growth and development by interacting with auxin signaling in Arabidopsis.