Ancient origin of plant CDPK family

CALÓ GF; SCHEIDEGGER D; MARTÍNEZ-NOËL G ; SALERNO GL

Foz Iguazú

Congreso; International Plant Molecular Biology; 2015

Calcium-dependent protein kinases (CDPKs) are an important group of proteins that sense calcium and acts as signal transductors in land plants. Recently it was also reported in the clorophyceae Chlamydomonas reindhartii. CDPK are highly conserved proteins and they play key roles in plant development and in environmental stress responses. To investigate the origin of plant CDPKs, we studied the occurrence of homologous sequences in the genome of the green algae Ostreococcus tauri, a tiny unicellular oxygenic photosynthetic eukaryote that belongs to Prasinophyceae, one of the most ancient groups within the green lineage. O. tauri has the most compact genome of a free-living eukaryote known to date. These characteristics make O. tauri a valuable model organism to perform functional and evolutive studies. We identified three sequences coding for putative proteins with the structural features of typical plant CDPK (OtCDPK1, OtCDPK2, and OtCDPK3), being OtCDPK1 and OtCDPK2 highly similar. Expression analysis by RT-PCR show that the three OtCDPK sequences are expressed and their transcription levels are regulated under nutritional deficiencies. Additionally, the functional characterization of the highest expressed OtCDPK was performed. Our results demonstrate that functional CDPKs occur in O. tauri, and that they are involved in stress responses. We conclude that Ca2+-CDPK signaling is present in an organism located at the base of the green lineage.