Journal Article

Heat tolerance in a wild Oryza species is attributed to maintenance of Rubisco activation by a thermally stable Rubisco activase ortholog

Michael E. Salvucci, Brian J. Atwell, Alexander Gallé, Elizabete Carmo-Silva, Andrew P. Scafaro, Jeroen Van Rie

2016

Overview

The mechanistic basis of tolerance to heat stress was investigated in Oryza sativa and two wild rice species, Oryza meridionalis and Oryza australiensis. The wild relatives are endemic to the hot, arid Australian savannah. Leaf elongation rates and gas exchange were measured during short periods of supraoptimal heat, revealing species differences. The Rubisco activase (RCA) gene from each species was sequenced. Using expressed recombinant RCA and leaf-extracted RCA, the kinetic properties of the two isoforms were studied under high temperatures. Leaf elongation was undiminished at 45°C in O. australiensis. The net photosynthetic rate was almost 50% slower in O. sativa at 45°C than at 28°C, while in O. australiensis it was unaffected. Oryza meridionalis exhibited intermediate heat tolerance. Based on previous reports that RCA is heat-labile, the Rubisco activation state was measured. It correlated positively with leaf elongation rates across all three species and four periods of exposure to 45°C. Sequence analysis revealed numerous polymorphisms in the RCA amino acid sequence from O. australiensis. The O. australiensis RCA enzyme was thermally stable up to 42°C, contrasting with RCA from O. sativa, which was inhibited at 36°C. We attribute heat tolerance in the wild species to thermal stability of RCA, enabling Rubisco to remain active.

• Publisher: New Phytologist Trust,Wiley Subscription Services, Inc
• Subject: Adenosine Triphosphate - metabolism / Amino Acid Sequence / amino acid sequences / Amino acids / Base Sequence / correlation / Enzyme Activation / Enzyme Stability / exposure duration / Gas exchange / genes / Genes, Plant / Genotype / heat / heat stress / Heat tolerance / High temperature / Hot Temperature / Hydrolysis / interspecific variation / leaves / Oryza / Oryza - enzymology / Oryza - genetics / Oryza - physiology / Oryza australiensis / Oryza meridionalis / Oryza sativa / Photosynthesis / Plant Proteins - genetics / Plant Proteins - metabolism / Plant Stomata - physiology / Recombinant Proteins - metabolism / ribulose-bisphosphate carboxylase / Ribulose-Bisphosphate Carboxylase - chemistry / Ribulose-Bisphosphate Carboxylase - genetics / Ribulose-Bisphosphate Carboxylase - metabolism / ribulose-bisphosphate carboxylase activase / rice (Oryza sativa) / Rubisco activase (RCA) / savannas / Sequence Alignment / sequence analysis / Species Specificity / temperature / thermal stability / Thermotolerance - physiology / wild relatives / wild rice