Expression of Proteins Involved in Host Plant Defense Against Greenbug Infestation

The greenbug, Italics - Schizaphis graminum - Italics (Rondani), has been recognized as a major pest of small grains, including sorghum and wheat. To understand the molecular mechanisms involved in host plant defense against greenbug aphids, a proteomic analysis of greenbug-induced proteins in the seedlings of sorghum was conducted at various times following greenbug infestation. Young seedlings of sorghum were infested by virulent greenbug for 5 days; then the total proteins of the greenbug-infested seedlings were extracted. After two-dimensional gel electrophoresis (2D-PAGE), seventy-seven proteins showed statistically significant differences in spot abundance. Of those greenbug-induced proteins, 52 were up-regulated and 25 were down-regulated in the resistant line; while thirty one significantly changed protein spots in the susceptible line were observed, with 16 of them up-regulated and 15 down-regulated. It was noticed that greenbug-responsive proteins were mainly involved in energy metabolism pathways, stress and defense, cell signaling and protein metabolism, indicating modulation of various cellular functions upon greenbug attack. Furthermore, sorghum response is characterized by a reduced accumulation of photosynthetic proteins and a modification of the expression of various cell wall related genes. These findings provide us the insight into the molecular events and defense mechanisms operating in the resistant plants in order to defend against greenbug aphids, which may be important information for development of new strategies of plant protection.