Proteomic analysis of heterosis during maize seed germination

Heterosis is observed for most phenotypic traits and developmental stages in many plants. In this study, the embryos, from germinating seeds after 24 h of soaking, for five elite maize hybrids and their parents were selected to unravel the genetic basis of heterosis using 2-D proteomic method. In total, 257 (80.06%), 363 (58.74%), 351 (79.95%), 242 (54.50%), and 244 (46.30%) nonadditively expressed proteins were identified in hybrids Zhengdan 958, Nongda 108, Yuyu 22, Xundan 20, and Xundan 18, respectively. The nonadditive proteins were divided into above high-parent (++; 811, 55.66%), high-parent (+; 121, 8.30%), partial dominance (+-; 249, 17.09%), low-parent (-; 30, 2.06%), below low-parent (- -; 62, 4.26%), and D (different; 184, 12.63%) expression patterns. The observed patterns indicate the important roles of dominance, partial dominance, and overdominance in regulating seed germination in maize. Additionally, 54 different proteins were identified by mass spectrometry and classified into nine functional groups: metabolism (9), cell detoxification (8), unknown functional proteins (8), chaperones (7), signal transduction (6), development process (5), other (5), transporter (3), and stress response (3). Of these, the most interesting are those involved with germination-related hormone signal transduction and the abscisic acid and gibberellin regulation networks.