Deciphering Arabidopsis Calmodulin-binding Protein IQ67-Domain (IQD) roles

TRIASSI, A; MARIA FABIANA DRINCOVICH; LARA, MV

Puerto Varas

Congreso; XII Panamerican Association for Biochemistry and Molecular Biology (PABMB) Congress; 2013

Ca2+ is a fundamental second messenger in cells. Calmodulins and Calmodulins -like proteins are among the more widespread Ca2+ sensors. A novel class of putative plant-specific Calmodulin/Calmodulin-like-targets is the IQ67-Domain (IQD) family protein. IQD members share a unique domain of multiple in tandem Calmodulin retention motifs, are structurally diverse in molecular mass but have some properties reminiscent of RNA binding proteins. Surprisingly little is known about their biological roles. In a very drought tolerant species Portulaca oleracea we previously identified, by a transcriptomic approach, the induction of a transcript ortologous to Arabidopsis thaliana IQD32 after withholding water. To decipher the role of this protein, we started to study it and two other members of the family (IQD28 and -30) in A. thaliana. The transcripts encoding them displayed the greatest expression in roots, followed by seeds, flower, stems and leaves. The response to different abiotic stress conditions was tested; their expression was greatly induced (12-fold) in roots after 3 hs of mannitol or NaCl treatments and decreased after 72 hs. Similarly in leaves, their expression increased after 3 hs of abscisic acid and manitol and reduced thereafter. We have cloned and expressed IQD28, -30 and-32 recombinant proteins and are currently testing their ability to bind calmodulin as well as looking for their targets.