Chen Lanzhuang, Guan Liming, Seo Misuk, Hoffmann Franz, Adachi Taiji
Gene Research Center, Miyazaki University, Japan.
J Plant Physiol. 2005 Oct;162(10):1141-8. doi: 10.1016/j.jplph.2005.02.010.
We have used Western blue-visualized in situ-hybridization (ISH) to monitor the expression of apomixis-specific gene-1 (ASG-1, GenBank accession number AB000809) during gametogenesis in obligate-sexual and facultative-apomictic (aposporic) genotypes of guinea grass (Panicum maximum). The in situ-analysis revealed that ASG-1 is not expressed in the ovule during early floral development in both, the facultative apomicts (A1 stage) and the obligate sexuals (S1 stage). With the appearance of the aposporous initial cell(s) in the ovule of the apomictic type (A2-1 stage), ASG-1 expression is strong and specific to this apomixis-specific cell. ASG-1 expression continued through different stages of aposporous embryo sac development (A2-2 stage), indicating that the gene may play a role in this developmental process. Regular embryo sacs in sexual types did not show hybridization signals (S2 stage). However, strong ASG-1 expression was detected in immature pollen grains and young embryos in both reproductive types, suggesting that ASG-1 may be an allele derived from the obligate-sexual wild type. Expression in pollen grains faded with maturation. In a heterologous system, using Paspalum notatum, a facultative-aposporic tropical grass (bahia grass), identical results were obtained. The results are discussed in view of the fact, that ASG-1 shows some homology to genes known to be seed- or embryo-specific or involved in processes related to cell growth.
我们利用 Western 蓝可视化原位杂交（ISH）技术，监测了大黍（Panicum maximum）专性有性生殖和兼性无融合生殖（无孢子生殖）基因型配子发生过程中无融合生殖特异性基因 1（ASG-1，GenBank 登录号 AB000809）的表达情况。原位分析表明，在兼性无融合生殖类型（A1 阶段）和专性有性生殖类型（S1 阶段）的早期花发育过程中，胚珠中均未检测到 ASG-1 的表达。随着无孢子生殖类型胚珠中无孢子初始细胞的出现（A2-1 阶段），ASG-1 表达强烈且特异性地出现在这种无融合生殖特异性细胞中。ASG-1 的表达在无孢子胚囊发育的不同阶段持续存在（A2-2 阶段），表明该基因可能在这一发育过程中发挥作用。有性生殖类型的正常胚囊未显示杂交信号（S2 阶段）。然而，在两种生殖类型的未成熟花粉粒和幼胚中均检测到强烈的 ASG-1 表达，这表明 ASG-1 可能是源自专性有性生殖野生型的一个等位基因。花粉粒中的表达随着成熟而减弱。在一个异源系统中，利用兼性无孢子热带禾本科植物巴伊亚雀稗（Paspalum notatum）进行实验，也获得了相同的结果。鉴于 ASG-1 与已知的种子或胚特异性基因或参与细胞生长相关过程的基因存在一些同源性，我们对这些结果进行了讨论。
