Proteomic Analyses of Maize Cross Incompatibility Gene Ga1-S

Ga1-S is a gametophytic mutant involved in maize cross incompatibility. The presence of the dominant allele Ga1-S in silks prevents fertilization by pollen carrying the recessive allele ga1. The physiological basis of cross incompatibility is poorly understood. The proteomic profiling of Ga1-S silks pollinated with Ga1-S and ga1 pollen was investigated for isolating genes involved in cross incompatibility in maize. Two near isogenic lines on Ga1-S locus, W22 (GG) and w22 (gg), were used to make reciprocally crosses of GG × GG, gg × GG, and GG × gg. The behaviours of pollen tube growth in the 3 crosses were compared under a fluorescence microscopy, and the proteomic profiles of total silk proteins in W22 (GG) were compared 10 h after pollination by GG or gg pollen. The total silk proteins of GG × GG and GG × gg crosses were extracted using TCA/Acetone method, separated through electrophoresis in 2-dimensional gels, and analyzed by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS). The results indicated that gg pollen grains germinated well and the pollen tubes were able to enter the GG silk transmitting tract. However, no gg pollen tube reached GG ovule area, which resulted in incompatibility. In the silk proteomes of GG × GG and GG × gg, 25 differentially expressed proteins were identified, including 15 specifically expressed in GG × GG, and 10 specifically expressed in GG × gg. Among these proteins, 12 were annotated in various databases after MALDI-TOF-MS and MASCOT analyses. Proteins 11, 12, 14, 18, 22, and 24 presumably play important roles in the cross-incompatibility of maize.

摘要为了研究玉米异交不亲和的蛋白表达机制, 以玉米(Zea mays L.)异交不亲和基因Gal-S的一对近等基因系W22(GG)与w22(gg)为材料, 组配自交(GG×GG)、正交(gg×GG)与反交(GG×gg) 3个组合。首先采用荧光显微技术, 观察比较了3个组合中花粉管在花丝中的生长过程; 其次采用IEF/SDS-PAGE双向凝胶电泳与基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)技术, 比较研究了授粉后10 h自交与反交母本W22(GG)花丝蛋白质组的特异表达差异。结果表明, 授粉后10 h, 自交与正交花粉管伸长可达花丝基部, 而反交花丝基部未观察到花粉管; 自交与反交母本W22(GG)花丝蛋白质组共检测到25个差异蛋白质点, 其中15个在自交中特异表达, 10个在反交中特异表达。通过MALDI-TOF-MS质谱测序和MASCOT序列分析, 注释了12个蛋白质点, 其中自交中特异表达的蛋白质点11、12、14和异交中特异表达的蛋白质点18、22、24可能与玉米异交不亲和密切相关。