RuBisCo activase—a catalytic chaperone involved in modulating the RuBisCo activity and heat stress-tolerance in wheat

Abstract

RuBisCo activase modulate the activity of RuBisCo and protect the nascent proteins from aggregation under heat stress (HS). Here, we have identified and cloned a putative RuBisCo activase (Rca) gene of 1402 bp from wheat cv. HD2985 using transcriptomic approach. Evolutionary search established the presence of 63 Orthologs and 2 Paralogs of the cloned Rca gene. Sequence analysis showed significant variations in the amino acid of Rca and RuBisCo (large and small subunit) in thermotolerant and thermosusceptible wheat cvs. Heterologous expression of Rca in E. coli showed the release of ~ 47 kDa purified protein. Expression analysis of Rca at transcript and protein level showed significant up-regulation in wheat cvs. Raj3765 (thermotolerant) and HD2329 (thermosusceptible) under HS. RuBisCo enzyme present in thermosusceptible cv. showed more sensitivity to HS, as compared to thermotolerant. Rca activity was observed higher in Raj3765 during pollination and milky-ripe stages under HS (38 °C, 1 h), as compared to HD2329. The binding of Rca with the RuBisCo under HS was observed more stable in Raj3765, as compared to HD2329. The purified Rca enzyme was observed more effective in the renaturation of RuBisCo (inactive) under HS in Raj3765 than in HD2329. A positive correlation was established between the Rca enzyme activity and radical scavenging potential in the leaves of both the wheat cvs. under HS. There is a need to characterize the enzyme kinetics and functional diversity of Rca in order to exploit it in a better way to augment the carbon assimilatory processes in wheat under differential HS.