Article

Physiological and molecular changes in Oryza meridionalis Ng., a heat-tolerant species of wild rice

Department of Biological Sciences, Macquarie University, NSW 2109, Australia.
Journal of Experimental Botany (Impact Factor: 5.53). 10/2009; 61(1):191-202. DOI: 10.1093/jxb/erp294
Source: PubMed

ABSTRACT

Oryza meridionalis Ng. is a wild relative of Oryza sativa L. found throughout northern Australia where temperatures regularly exceed 35 °C in the monsoon growing season. Heat tolerance
in O. meridionalis was established by comparing leaf elongation and photosynthetic rates at 45 °C with plants maintained at 27 °C. By comparison
with O. sativa ssp. japonica cv. Amaroo, O. meridionalis was heat tolerant. Elongation rates of the third leaf of O. meridionalis declined by 47% over 24 h at 45 °C compared with a 91% decrease for O. sativa. Net photosynthesis was significantly higher in O. sativa at 27 °C whereas the two species had the same assimilation rates at 45 °C. The leaf proteome and expression levels of individual
heat-responsive genes provided insight into the heat response of O. meridionalis. After 24 h of heat exposure, many enzymes involved in the Calvin Cycle were more abundant, while mRNA of their genes generally
decreased. Ferredoxin-NADP(H) oxidoreductase, a key enzyme in photosynthetic electron transport had both reduced abundance
and gene expression, suggesting light reactions were highly susceptible to heat stress. Rubisco activase was strongly up-regulated
after 24 h of heat, with the large isoform having the largest relative increase in protein abundance and a significant increase
in gene expression. The protective proteins Cpn60, Hsp90, and Hsp70 all increased in both protein abundance and gene expression.
A thiamine biosynthesis protein (THI1), previously shown to act protectively against stress, increased in abundance during
heat, even as thiamine levels fell in O. meridionalis.

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    • "Journal of Agricultural Science Vol. 8, No. 2; 2016 negative effects of the supra-optimal temperatures on gas exchange variables were evident, decreasing the photosynthesis values; on the other hand, there was an increase of gs, E and ci:ca, indicating that photosynthesis reduction cannot be attributed to progressive decrease in the fluxes of CO 2 concentration reaching the chloroplasts. In this sense, there are studies showing that photosynthesis declines at moderate heat-stress can result from a decrease in the activation state of rubisco, via a loss of carbamylation capacity due to changes in stromal pH and Mg +2 concentration (Fukayama et al., 2011; Hammond, Andrews, & Woodrow, 1998; Salvucci & Crafts-Brandner, 2004; Scafaro et al., 2010). Therefore, temperature effects are generally attributed to variation of ion concentration in the stroma because of unspecified changes in the properties of the thylakoid membranes (Vani, Saradhi, & Mohanty, 2001; Weis, 1981). "

    Full-text · Dataset · Feb 2016
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    • "Journal of Agricultural Science Vol. 8, No. 2; 2016 negative effects of the supra-optimal temperatures on gas exchange variables were evident, decreasing the photosynthesis values; on the other hand, there was an increase of gs, E and ci:ca, indicating that photosynthesis reduction cannot be attributed to progressive decrease in the fluxes of CO 2 concentration reaching the chloroplasts. In this sense, there are studies showing that photosynthesis declines at moderate heat-stress can result from a decrease in the activation state of rubisco, via a loss of carbamylation capacity due to changes in stromal pH and Mg +2 concentration (Fukayama et al., 2011; Hammond, Andrews, & Woodrow, 1998; Salvucci & Crafts-Brandner, 2004; Scafaro et al., 2010). Therefore, temperature effects are generally attributed to variation of ion concentration in the stroma because of unspecified changes in the properties of the thylakoid membranes (Vani, Saradhi, & Mohanty, 2001; Weis, 1981). "
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