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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    • "However, there were also many inconsistencies between these studies. An intriguing discrepancy was that in Chlamydomonas we could not detect any increase in the abundance of proteins involved in redox regulation/scavenging of reactive oxygen species, which was observed in several studies on land plants (Ferreira et al., 2006; Lee et al., 2007; Palmblad et al., 2008; Xu and Huang, 2008; Scafaro et al., 2010). Whether these inconsistencies were due to different durations of HS monitored, the different methodologies applied (2D- PAGE versus shotgun proteomics), or organism-specific responses remained unclear. "
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    The Plant Cell 11/2014; 26(11). DOI:10.1105/tpc.114.130997 · 9.34 Impact Factor
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    • "Likewise, new insights were gained related to HSPs and regulatory proteins , energy metabolism and redox homeostasis by applying MALDI-TOF MS in rice (Lee et al. 2007). Leaf proteome analysis of wild rice O. meridionalis (under HS at 45°C) manifested differential response of heat-responsive genes and encouraged enzymes associated with Calvin cycle and thiamine biosynthesis (Scafaro et al. 2010). Thirteen differentially expressed protein spots identified by MASS/MALDI-TOF analysis under HS during anthesis shed new light on the mechanism of HT in rice (Jagadish et al. 2010b). "
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    • "This shift in flowering time toward the cooler early morning resulted in significantly lower high-temperatureinduced spikelet sterility. Scafaro et al. (2010) have additionally reported that Oryza meridionalis, a wild relative of O. sativa, displays greater hightemperature tolerance than O. sativa, as shown by comparing leaf elongation , photosynthetic rates, and accumulation of heat-induced proteins. "
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