Functional analysis of the extracellular domains of pollen receptor kinases LePRK1 and LePRK2 from tomato.

DE PAZ SIERRA, PABLO; SALEM, TAMARA; WENGIER, DIEGO; CABANAS, MARIA; MUSCHIETTI, JORGE

PINAMAR, ARGENTINA

Congreso; SAIB 2005; 2005

SAIB

LePRK1 and LePRK2 are two pollen-specific receptor kinases from Solanum lycopersicon (tomato) that are localized at the plasma membrane of the pollen tube. Both LePRK1 and LePRK2 can be co-immunoprecipitated from pollen or when expressed together in yeast. The addition of tomato or tobacco style extracts specifically disrupts this interaction. We constructed three types of cytoplasmic deletion constructs for both LePRK1 and LePRK2. All of them lacked the extracellular N-terminal domain (ECD) and bore different portions of the cytoplasmic domains (CD). Each deletion construct of one receptor was properly co-expressed in yeast with the corresponding full-length construct of the other receptor. Results obtained by co-immunoprecipitation assays showed that the kinase domain of LePRK2 is necessary for the interaction with LePRK1. We also made two constructs that had the ECD and lacked totally or partially the CDs. Co-immunoprecipitation assays showed that the ECD of each receptor are sufficient for their interaction. Contrary to the interaction between full-length LePRK1 and LePRK2, tobacco style extracts did not disrupt the interaction between any of the ECD deletion constructs and the corresponding full-length. All these results suggest that the LePRK2 kinase domain is responsible for the interaction and lead us to propose that the ECDs, after binding to the style ligand, activate the CDs transducing the signal through complex dissociation.