TCP14 and TCP15 regulate leaf trichome branching

CAMOIRANO, ALEJANDRA; VIOLA, IVANA L; GONZALEZ, DANIEL H

Buenos Aires

Simposio; Fronteras en Biociencia 3; 2018

IBioBA, CONICET ? Partner Institute of the Max Planck Society

The TCPproteins are plant-specific transcription factors involved in the regulation ofdiverse aspects of plant development including lateral organ morphogenesis bymodulating cell proliferation and differentiation. TCPs have a conserved domainof 59 amino acids that is involved in DNA binding and dimerization. Based ondistinctive features present both within and outside this domain, TCPs aredivided into two classes: I and II.We foundthat members of class I TCP proteins from Arabidopsisthaliana, TCP14 and TCP15, suppress trichome branching in Arabidopsisleaves. In loss-of-function mutants in TCP14, TCP15 and TCP14/TCP15 the trichome branch number is increased. Whereas theleaves of wild-type plants have most trichomes of three branches and some ones oftwo branches, tcp14 tcp15 show asimilar proportion of trichomes of three and four branches and also presentstrichomes of five branches; not having differences in trichome number. MIXTA-liketranscription factors MYB16 and MYB106/NOK, were reported to suppress trichomebranching. In a global analysis of gene expression with plants expressing pTCP15:TCP15fused to the EAR repressor domain, we found that MYB16 and NOK aresignificantly repressed. In addition, tcp14tcp15 plants also present reduced levels of transcripts of MYB16 and NOK. Accordingly, plants transformed with pMYB16:GUS and pNOK:GUS displayed more reporter activity when TCP15 is overexpressed. Also,it has been observed that the number of branches depends on the content ofnuclear DNA related to the endoreduplication process. Thus, theexpression of different cell cycle genes that are negatively regulated duringentry into endoreduplication cycles was measured. tcp14 tcp15 plants presented reduced expression levels of CYCA2; 3, CYCB1; 1, RBR1 and PCNA1. Then we cuantified trichome DNAcontent by staining with DAPI, and found that tcp14 tcp15 plants present more DNA content indicating moreendoreduplication, wich may cause more trichome branching. Takentogether, our results suggests that TCPI proteins inhibit the development oftrichome branches, regulating endoreduplication and also through the regulationof the expression of NOK and MYB16.