A Proteomics Analysis of Drought Stress-Responsive Proteins as Biomarker for Drought-Tolerant Sugarcane Cultivars

Problem statement: The prime objective in breeding selection process of drought-tolerant sugarcane is to identify the correlating marker, which could lead to rapid screening for drought-tolerant cultivars. In this study, we have reported an unknown 18-kDa protein (p18) along with other stress-inducible proteins to be highly expressed in sugarcane leaves under drought stress condition. Approach: The 2D-PAGE patterns of proteins were compared between those expressed in drought-tolerance K86-161 and drought-susceptible Khon Kaen 1 cultivars. The interested proteins were identified by mass spectrometry. The correlation between p18 expression and drought tolerance was verified in additional 4 sugarcane cultivars using ELISA and western blotting. Two physiological indexes, Chlorophyll content and SOD activity were also evaluated. Results: Mass spectrometry and comparison with known sequences in the database reveal that the proteins expressed only in stressed K86-161 are serine protease inhibitor and the one similar to replication protein A1. A group of proteins up-regulated in K86-161 are S-Adenosylmethionine decarboxylase proenzyme (SAM), ubiquitin and p18. From ELISA and western blotting analysis, we found that p18 expressed in drought-tolerant sugarcane cultivars had higher binding specificity to antibody than that in drought-susceptible sugarcane cultivars. Two physiological indexes showed higher levels in drought-tolerant than those in drought susceptible sugarcanes. Conclusion: These high levels of chlorophyll and SOD are in agreement with a high level of p18 expression in drought-tolerant sugarcanes. It is likely that an accumulation of p18 is a response to water deficit. In conclusion, p18 might be a good candidate for development as a marker in drought-tolerant plants.