TCP14 and TCP15 regulate leaf trichome branching

ALEJANDRA CAMOIRANO; DANIEL GONZALEZ; IVANA VIOLA

Buenos Aires

Simposio; Simposio Fronteras en Biociencia 3; 2018

Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA, CONICET ? Partner Institute of the Max Planck Society)

The TCP proteins are plant-specific transcription factors involved in the regulation of diverse aspects of plant development. TCPs have a conserved domain of 59 amino acids that is involved in DNA binding and dimerization. Based on distinctive features present both within and outside this domain, TCPs are divided into two classes: I and II. We found that two members of class I from Arabidopsis thaliana, TCP14 and TCP15, suppress trichome branching in leaves. Whereas most trichomes in the leaves of wild-type plants have three branches, tcp14, tcp15 and double tcp14 tcp15 mutants show a similar proportion of trichomes with three and four branches and also present trichomes with five branches. In a global analysis of gene expression with plants expressing TCP15 fused to the EAR repressor domain, we found that MYB16 and MYB106/NOK, two MIXTA-like transcription factors that suppress trichome branching, are significantly repressed. This was also observed in tcp14 tcp15 plants. Accordingly, plants transformed with pMYB16:GUS and pNOK:GUS displayed increased reporter activity when TCP15 was overexpressed. The expression of cell cycle genes related to cell division, like CYCA2; 3, CYCB1;1, RBR1 and PCNA1, is also reduced in tcp14 tc1p15 plants, which also showed an increase in trichome DNA content, indicative of increased endoreduplication. This is consistent with reports indicating that trichome branching correlates with the content of trichome nuclear DNA. Taken together, our results suggests that TCP proteins inhibit the development of trichome branches through the regulation of endoreduplication and MIXTA-like transcription factors.