Proteomic Analysis of Sugarcane Stalk Response to Cold Stress.

Cold stress is a major abiotic stress limiting sugarcane (Saccharum officenarum L.) growth and productivity in many areas in the world. Proteomic studies were conducted to better understand the molecular adaptation mechanisms of cold stress in two sugarcane varieties: GT28 (cold-resistant) and YL6 (cold-susceptible). Two different temperature regimes were used (0 ºC, cold stress and 25 ºC, control) and the plants at early ripening stage were exposed to cold-stress for six days.  Total proteins were extracted from the stalk tips collected from both cold stress and control.  By fractionation, approximately 1000 protein spots were separated and visualized on silver-stained with two-dimensional (2-D) gels. Forty protein spots showed at least 2-fold change in response to the cold stress. Among those protein spots, 12 increased while13 decreased in both varieties. Moreover, 9 proteins were up-regulated and 3 down-regulated in GT28, while they were opposite to YL6 in that 9 decreased and 3 increased.  Spot identification was performed by MALDI-TOF-MS. Their functional category distributions are involved in defense response, cytoskeleton, metabolism, energy, and signal transduction. Using immunohistochemistry and Western blot, the subcellular localization and expression of the identified α-tubulin were analyzed, and found to obviously decrease in YL6 under cold stress, implying that cytoskeleton is virtually subjective to cold stress in the susceptible variety.  Many of the identified proteins can be described in the context of cold-stress responses, indicating the validity of the proteome approach.

Key words:  Cold stress; protein; sugarcane