Molecular and Biochemical Analysis of Calreticulin

Calreticulin (CRT) deals with misfolded proteins by binding to them and marking them for degradation so that only the properly folded proteins are allowed to move away from the ER. It is predicted that a downstream mitogen-activated protein kinase may mediate this phosphorylation. Therefore, salicylic acid treatment was used to enhance the expression in CRT gene in tomato. The activity of ERK sub-group of MAPK can be inhibited by ERK inhibitors. The ERK inhibitor interrupted the physical interaction of ERK-type MAPKs and their upstream MAPKKs. Unfolded protein response (UPR) caused by the ER stress was induced by tunicamycin (TM) or dithiothreitol (DTT). Expression cloning of CRT in E.coli was conducted and the expression of CRT protein was examined by SDS-PAGE and Western blotting. Two enzymes, β-1, 3-glucanase (PR2) and glutamine synthetase, were also examined under stress treatment. It is hoped that this work would produce new knowledge into diverse aspects of MAPK pathways to facilitate comprehensive and molecular understanding of the complex defense system. The discoveries will lay the ground for knowledge-based innovative strategies to reduce the impact of plant diseases.