title: Heat tolerance in a wild Oryza species is attributed to maintenance of Rubisco activation by a thermally stable Rubisco activase ortholog.
abstract: 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 supra-optimal 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.
authors.affiliation: Department of Biological Sciences, Faculty of Science and Engineering, Macquarie University, Sydney, NSW, 2109, Australia.|ARC Centre of Excellence in Plant Energy Biology, Research School of Biology, The Australian National University, Canberra, ACT, 0200, Australia.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Scafaro
authors.affiliation: Bayer CropScience NV, Innovation Center - Trait Research, Technologiepark 38, Zwijnaarde (Gent), 9052, Belgium.
authors.forename: Alexander
authors.initials: A
authors.lastname: Gallé
authors.affiliation: Bayer CropScience NV, Innovation Center - Trait Research, Technologiepark 38, Zwijnaarde (Gent), 9052, Belgium.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Van Rie
authors.affiliation: Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK.
authors.forename: Elizabete
authors.initials: E
authors.lastname: Carmo-Silva
authors.affiliation: US Department of Agriculture, Agricultural Research Service, Arid-Land Agricultural Research Center, Maricopa, AZ, 85138, USA.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Salvucci
authors.affiliation: Department of Biological Sciences, Faculty of Science and Engineering, Macquarie University, Sydney, NSW, 2109, Australia.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Atwell
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D004789:Enzyme Activation; D004795:Enzyme Stability; D017343:Genes, Plant; D005838:Genotype; D006358:Hot Temperature; D006868:Hydrolysis; D012275:Oryza / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D010788:Photosynthesis; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D054046:Plant Stomata / Q000502:physiology; D011994:Recombinant Proteins / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D013045:Species Specificity; D000071436:Thermotolerance / Q000502:physiology*
chemical_list: D010940:Plant Proteins; D011994:Recombinant Proteins; C054765:rca protein, plant; D000255:Adenosine Triphosphate; D012273:Ribulose-Bisphosphate Carboxylase
keywords: Oryza australiensis; Oryza meridionalis; Rubisco activase (RCA); heat tolerance; photosynthesis; rice (Oryza sativa); thermal stability