Zhao et al: Floral TCP-MADS box transcription factor networks

13.10.2020
New paper of Zhao et al. (Plant Physiology, 2020) shows how development of marginal ray flowers in Asteraceae flower heads is regulated by a dynamic network of CINCINNATA- and SEPALLATA-like transcription factors upstream of a CYCLOIDEA-like gene.

Link to the paper: https://doi.org/10.1104/pp.20.00702

Recognizing the first author profile, Yafei Zhao: https://plantae.org/recognizing-plant-physiology-authors-yafei-zhao/

Highlight of our paper by Yunqing Yu: CYCLOIDEA3 Is Targeted by Disparate Transcription Factors in Patterning Flowers in Gerbera, http://www.plantphysiol.org/content/184/3/1214?etoc=&utm_source=TrendMD&utm_medium=cpc&utm_campaign=Plant_Physiol_TrendMD_0

This work has been funded by the Academy of Finland (grants 139092 and 310318 for PE), and by Jenny and Antti Wihuri Foundation and the Finnish Cultural Foundation grants (YZ).

Abstract

The large sunflower family, Asteraceae, is characterized by compressed, flower-like inflorescences that may bear phenotypically distinct flower types. The CYCLOIDEA/TEOSINTE BRANCHED1 (CYC/TB1)-like transcription factors (TFs) belonging to the TEOSINTE BRANCHED 1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) protein family are known to regulate bilateral symmetry in single flowers. In Asteraceae, they function at the inflorescence level, and were recruited to define differential flower type identities. Here, we identified upstream regulators of GhCYC3, a gene that specifies ray flower identity at the flower head margin in the model plant Gerbera hybrida. We discovered a previously unidentified expression domain and functional role for the paralogous CINCINNATA-like (CIN) TCP proteins. They function upstream of GhCYC3 and affect the developmental delay of marginal ray primordia during their early ontogeny. At the level of single flowers, the Asteraceae CYC genes show a unique function in regulating the elongation of showy ventral ligules that play a major role in pollinator attraction. We discovered that during ligule development, the E class MADS-box TF GRCD5 activates GhCYC3 expression. We propose that the C class MADS-box TF GAGA1 contributes to stamen development upstream of GhCYC3. Our data demonstrate how interactions among and between the conserved floral regulators, TCP and MADS-box TFs, contribute to the evolution of the elaborate inflorescence architecture of Asteraceae.