The TCP domain mediates the antagonistic action of TCP8 and TCP23 on flowering in Arabidopsis

ALEJANDRA CAMOIRANO; DANIEL GONZALEZ; IVANA VIOLA

Cordoba

Congreso; LII Reunión anual de la SAIB; 2016

SAIB

TCP transcription factors are plant-specific proteins that share the TCP domain, responsible for DNA binding and dimerization. TCPs are key factors in plant growth and development and they are classified in two classes: I and II. We found that two members of class I from Arabidopsis thaliana, TCP8 and TCP23, regulate flowering time in an opposite manner. A loss-of-function mutant in TCP8 has a late flowering phenotype while plants that express TCP8 from the 35SCaMV promoter flower earlier that wild type. On the contrary, overexpression lines of TCP23 show a delayed transition to flowering. Analysis of the expression patterns conferred by the TCP8 and TCP23 promoter regions revealed that both genes are expressed in the apical meristem. To analyze the molecular basis governing the opposite action of these proteins, we overexpressed four chimeric proteins between TCP8 and TCP23 in plants and found that the TCP domain would be the responsible for the observed effects on flowering. While both TCP domains are highly similar, TCP23 presents a substitution in a highly conserved residue that may alter the secondary structure of the HLH motif. We are currently investigating how this substitution changes the functional properties of the TCP domain.