A subcellular tug of war involving three MYB‐like proteins underlies a molecular antagonism in Antirrhinum flower asymmetry

Abstract

These two authors contributed equally to this work. SUMMARYThe establishment of meristematic domains with different transcriptional activity is essential for many developmental processes. The asymmetry of the Antirrhinum majus flower is established by transcription factors with an asymmetric pattern of activity. To understand how this asymmetrical pattern is established, we studied the molecular mechanism through which the dorsal MYB protein RADIALIS (RAD) restricts the activity of the MYB transcription factor DIVARICATA (DIV) to the ventral region of the flower meristem. We show that RAD competes with DIV for binding with other MYB-like proteins, termed DRIF1 and DRIF2 (DIVand-RAD-interacting-factors). DRIF1 and DIV interact to form a protein complex that binds to the DIV-DNA consensus region, suggesting that the DRIFs act as co-regulators of DIV transcriptional activity. In the presence of RAD, the interaction between DRIF1 and DIV bound to DNA is disrupted. Moreover, the DRIFs are sequestered in the cytoplasm by RAD, thus, preventing or reducing the formation of DRIF-DIV heterodimers in the nuclei. Our results suggest that in the dorsal region of the Antirrhinum flower meristem the dorsal protein RAD antagonises the activity of the ventral identity protein DIV in a subcellular competition for a DRIF protein promoting the establishment of the asymmetric pattern of gene activity in the Antirrhinum flower.

Control of Floret Symmetry by RAY3, SvDIV1B, and SvRAD in the Capitulum of Senecio vulgaris

“…interacting with SvDIV1B as in other species (Raimundo et al, 2013). However, to confirm this hypothesis, the function of SvRAD needs to be further investigated.…”

“…Floral bilateral symmetry in A. majus involves the action of CYC and DICH that activate RAD, which in turn down-regulates DIV activity in dorsal petals (Raimundo et al, 2013;Corley et al, 2005;Costa et al, 2005;Almeida et al, 1997). However, there has been no evidence as to whether DIV can feedback to regulate these genes during flower development.…”

“…The DIV gene promotes ventral petal identity and loss of DIV function leads to lateralized ventral petals (Almeida et al, 1997). RAD acts antagonistically to DIV (Corley et al, 2005), repressing its activity in the dorsal petals and causing DIV activity to be restricted to the ventral and lateral petals (Hileman, 2014;Raimundo et al, 2013).…”

How can an understanding of plant–pollinator interactions contribute to global food security?

“…The symmetry of a flower influences how easily a pollinator can acquire the reward by specifying the presence and position of landing platforms and occluded palates that require force to open. In Antirrhinum majus a transcriptional network comprising TCP and MYB family transcription factors has been shown to specify zygomorphy (bilateral symmetry) [69][70][71][72]. The mutants generated during these studies have provided insight into how pollinators forage to optimise their energy return.…”

Conversion of Abaxial to Adaxial Petal in a Torenia (<i>Torenia fournieri</i> Lind. ex Fourn.) Mutant Appeared in Selfed Progeny of the Mutable Line “Flecked”

“…Although DIV is an important player in ventral petal identity (Galego and Almeida, 2002;Rose et al, 1999), it is expressed in both ventral and dorsal petals (Almeida et al, 1997;Galego and Almeida, 2002). Recently, it has been shown that RAD negatively regulates DIV function via protein-protein interaction (Raimundo et al, 2013). DIV must form a heterodimer with another MYB protein, DIV-and-RAD-interacting-factor (DRIF), to function as a transcription factor in establishment of ventral petal identity.…”