Overexpression of the Ca2 -binding protein calreticulin in the endoplasmic reticulum improves growth of tobacco cell suspensions (Nicotiana tabacum) in high-Ca2 medium

Abstract

Calreticulin (CRT) is a eukaryotic, highly conserved, Ca 2+-binding protein predominantly located in the endoplasmic reticulum (ER) lumen. In addition to being involved in the regulation of cellular Ca 2+, calreticulin is a key quality control element during protein folding in the ER lumen. Tobacco (Nicotiana tabacum L.) suspension cells overexpressing a maize CRT (CRT1a) were used here to examine the properties of CRT in growing plant cells with respect to stress exposure. The endogenous CRT gene was induced rapidly after subculturing of the cells to new medium. In accordance, the CRT protein levels increased, peaking at days 3-4. At day 5, when the CRT transcript levels had levelled off, a..