Abstract
Using a series of multiplexed experiments we studied the quantitative changes in protein abundance of three Australian bread wheat cultivars (Triticum aestivum L.) in response to a drought stress. Three cultivars differing in their ability to maintain grain yield during drought, Kukri (intolerant), Excalibur (tolerant), and RAC875 (tolerant), were grown in the glasshouse with cyclic drought treatment that mimicked conditions in the field. Proteins were isolated from leaves of mature plants and isobaric tags were used to follow changes in the relative protein abundance of 159 proteins. This is the first shotgun proteomics study in wheat, providing important insights into protein responses to drought as well as identifying the largest number of wheat proteins (1,299) in a single study. The changes in the three cultivars at the different time points reflected their differing physiological responses to drought, with the two drought tolerant varieties (Excalibur and RAC875) differing in their protein responses. Excalibur lacked significant changes in proteins during the initial onset of the water deficit in contrast to RAC875 that had a large number of significant changes. All three cultivars had changes consistent with an increase in oxidative stress metabolism and reactive O2 species (ROS) scavenging capacity seen through increases in superoxide dismutases and catalases as well as ROS avoidance through the decreases in proteins involved in photosynthesis and the Calvin cycle.
Highlights
Abiotic stresses are the major cause of grain yield loss, upward of 50% (Boyer, 1982), and have significant impact on our capacity to meet the food demands of an ever increasing global population (Tester and Langridge, 2010)
Photosynthesis is reduced under a water deficit either through stomatal closure or metabolic impairment (Reddy et al, 2004) and changes in mitochondrial respiration and the photosynthetic electron transport lead to the generation of highly toxic reactive O2 species (ROS) such as superoxide and peroxides, that cause chemical damage to DNA and proteins leading to serious effects on cellular metabolism (Mittler, 2002)
Three wheat cultivars differing in their ability to maintain grain yield under drought conditions were studied
Summary
Abiotic stresses (e.g., drought, heat, and salinity) are the major cause of grain yield loss, upward of 50% (Boyer, 1982), and have significant impact on our capacity to meet the food demands of an ever increasing global population (Tester and Langridge, 2010). Plants have evolved several strategies to deal with ROS, including avoidance such as anatomical adaption, suppression of photosynthesis and photosystem (PS), and antenna modulations, ROS scavenging through the production of chemical antioxidants such as ascorbate and glutathione, and enzymes such as peroxidases and superoxide dismutases (SODs; Chaves et al, 2003; Mittler, 2006). Another adaptive mechanism to deal with drought is to maintain turgor pressure by the production of osmolytes, such as proline, glycine betaine, and trehalose that can provide secondary protective effects such as protecting proteins from unfolding (Hare et al, 1998). Drought responsive proteins such as dehydrins and heat shock proteins are produced to protect the intracellular metabolic machinery (Wang et al, 2003)
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