Comparative proteomic responses of Cleome spinosa (C3) and Cleome gynandra (C4) plants under drought stress

Drought stress caused by soil and atmospheric water deficiency is one of the most significant environmental factors affecting plant growth and productivity in the world. There are significant differences in the tolerance of plants to drought stress depending upon the carboxylation pathway. C4 plants, in contrast to C3 plants, are known to be better adapted to water stress. Although the mechanisms by which plants adapt to drought stress has been studied extensively at proteome level, the adaptive strategies of C3 and C4 plants grown under drought stress remain undefined. To determine the effects of drought stress on proteome changes, we used two-dimensional polyacrylamide gel electrophoresis (2-DE) and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry in the leaves of Cleome spinosa (C3) and C. gynandra (C4) plants. Totally 96 expressed differently protein spots were detected on 2-DE gels, of which 65 were identified by MALDI-TOF/TOF mass spectrometry. In both species, proteins related to photosynthesis and energy metabolism were predominantly affected under drought stress. Although the abundance of RuBisCO small subunits was increased in C. spinosa, the abundance of RuBisCO activase proteins was decreased. Furthermore the abundance of proteins related to light reactions of photosynthesis such as OEE and FNR proteins was decreased in C. spinosa. Under drought stress, the abundance of glycolysis-related proteins such as triosephosphate isomerase and fructose-bisphosphate aldolase was decreased in C. spinosa; however, enolase protein increased in C. gynandra. The chloroplastic ATP synthase enzyme was down-regulated also in both species under drought stress, while the mitochondrial ATP synthase up-regulated. The abundance of signal transduction-related proteins such as annexin and 14-3-3 proteins were increased in C. spinosa. The abundance of reactive oxygen species detoxification related proteins was generally increased in both species. These findings would lead to an improved understanding of the proteomic responses of the species differing in carboxylation pathway under drought stress.