Oral Paper

         Development and Structure

Virus induced over expression (VOX) in the ranunculid Thalictrum thalictroides supports a novel role for a MIXTA-like ortholog in stigmatic papillae during the evolution of wind pollination

Presenting Author
Veronica Di Stilio
Description
The MYB family of transcription factors one of largest in plants of genes playing key roles in regulatory processes during plant development. One of these genes is MIXTA/MIXTA-like, known to modulate the differentiation of distinct cell identities in the epidermis of land plants. We had previously investigated the evolutionary history and function of the MIXTA-like gene family in the ranunculid Thalictrum, a representative of early-diverging eudicots, and found a lineage-specific duplication coinciding with a Whole Genome Duplication (WGD) in one large clade within the genus. We then functionally characterized a MIXTA-like ortholog from the diploid species T. thalictroides (TthMYBML2) via targeted virus induced gene silencing (VIGS) in leaves, finding a role a trichomes. Here, we add experiments in floral tissue and report for the first time the successful use of virus induced overexpression (VOX) to support a novel role for Thalictrum MIXTA-like in stigmatic papillae. Overexpression assays in a heterologous system (tobacco) provided further evidence for the leaf trichome function, while supporting the novel role in the promotion of stigmatic papillae elongation. The latter finding, combined with the high differential expression of specific paralogs in carpels of wind-pollinated polyploid Thalictrum suggests that MIXTA-like duplications likely contributed to the development of long stigmatic papillae in feathery stigmas during the evolutionary transition from insect to wind pollination.