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

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.

Systems-Wide Analysis of Acclimation Responses to Long-Term Heat Stress and Recovery in the Photosynthetic Model OrganismChlamydomonas reinhardtii

“…While abundances of proteins involved in ROS scavenging did not change or even decreased during the first 3 h of HS (Mühlhaus et al, 2011), their accumulation after 24 h of HS can be clearly considered as a late response to HS. This also is in line with previous proteomics studies on different land plant species exposed to HS for more than 6 h, where levels of proteins like superoxide dismutase, thioredoxin h, ascorbate peroxidase, and dehydroascorbate reductase have been found to increase (Ferreira et al, 2006;Lee et al, 2007;Xu and Huang, 2008;Scafaro et al, 2010).…”

“…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.…”

“…When comparing results on Chlamydomonas with proteomics studies conducted on various land plants (Skylas et al, 2002;Majoul et al, 2003Majoul et al, , 2004Süle et al, 2004;Ferreira et al, 2006;Lee et al, 2007;Palmblad et al, 2008;Valcu et al, 2008;Xu and Huang, 2008;Scafaro et al, 2010;Xu and Huang, 2010), we concluded that the upregulation of chaperones, FKBP65 orthologs, and thiamine biosynthesis protein and the downregulation of ferredoxin-NADP(H) oxidoreductase, Rubisco, methionine synthase, adenosylhomocysteinase, and S-adenosylmethionine synthetase are conserved in the green lineage. However, there were also many inconsistencies between these studies.…”

Does Abiotic Stress Cause Functional B Vitamin Deficiency in Plants?

“…Gene expression data were taken from AtGenExpress and literature summarized in Supplemental Table S2. stress; the induction of THI4 relative to unstressed controls ranged from 14-to 44-fold (Zhu et al, 2013). It is equally striking that the THI4 protein showed, among all proteins analyzed, the second largest increase in expression (3.2-fold) in heat-stressed poplar leaves (Ferreira et al, 2006) and the third largest increase in expression (3.7-fold) in heat-stressed wild rice leaves (Scafaro et al, 2010). Like other organisms, plants have enzyme systems that deal with some of the chemical and enzymatic damage reactions shown in Figure 1 (Linster et al, 2013).…”

In Vitro Characterization of Thermostable CAM Rubisco Activase Reveals a Rubisco Interacting Surface Loop

“…Like most plants, rice possesses two isoforms of Rca, which are the product of alternative mRNA splicing and yield a 46-kD Rcaa and a 43-kD Rcab gene product, which differ at the C termini. In rice, the two isoforms are not equally expressed; Rcab is more abundant than Rcaa in both O. sativa (Wang et al, 2010) and the wild rice Oryza meridionales (Scafaro et al, 2010). These studies also reported that in both species, heat stress resulted in a relative increased abundance of Rcaa; however, thermostability of the purified isoforms was found to be similar (Scafaro et al, 2016).…”