Role of calreticulin in biotic and abiotic stress signalling and tolerance mechanisms in plants

Calreticulin (CRT) is calcium binding protein of endoplasmic reticulum (ER) which performs plethora of functions besides it's role as molecular chaperone. Among the three different isoforms of this protein, CRT3 is most closely related to primitive CRT gene of higher plants. Based on their distinct structural and functional organisation, the plant CRTs have been known to contain three different domains: N, P and the C domain. The domain organisation and various biochemical characterstics of plant and animal CRTs are common with the exception of some differences. In plant calreticulin, the important N-glycosylation site(s) are replaced by the glycan chain(s) and several consensus sequences for in vitro phosphorylation by protein kinase CK2 (casein kinase-2), are also present unlike the animal calreticulin. Biotic and abiotic stresses play a significant role in bringing down the crop production. The role of various phytohormones in defense against fungal pathogens is well documented. CRT3 has been reported to play important role in protecting the plants against fungal and bacterial pathogens and in maintaining plant innate immunity. There is remarkable crosstalk between CRT mediated signalling and biotic, abiotic stress, and phytohormone mediated signalling pathways The role of CRT mediated pathway in mitigating biotic and abiotic stress can be further explored in plants so as to strategically modify it for development of stress tolerant plants. •Calreticulin (CRT) is a calcium binding protein found mainly in the endoplasmic reticulum although now it is found to be reported in the nucleus and also in the cytosol.•There are three different isoforms of CRT found in plants and the CRT3 isoform is the one which is most closely related to the ancestral plant CRT gene.•CRT3 is found to confer innate immunity to plants by providing ressistance against fungal and bacterial pathogens.•There is a crosstalk between phytohormone signaling and CRT mediated pathway in preventing stress in plants.•All these aspects with relation to providing a strategy related to CRT in providing mechanism responsible for providing tolerance in plants can be explored.