Brown S M, Crouch M L
Biology Department, Indiana University, Bloomington 47405.
Plant Cell. 1990 Mar;2(3):263-74. doi: 10.1105/tpc.2.3.263.
We have isolated and characterized cDNA clones of a gene family (P2) expressed in Oenothera organensis pollen. This family contains approximately six to eight family members and is expressed at high levels only in pollen. The predicted protein sequence from a near full-length cDNA clone shows that the protein products of these genes are at least 38,000 daltons. We identified the protein encoded by one of the cDNAs in this family by using antibodies to beta-galactosidase/pollen cDNA fusion proteins. Immunoblot analysis using these antibodies identifies a family of proteins of approximately 40 kilodaltons that is present in mature pollen, indicating that these mRNAs are not stored solely for translation after pollen germination. These proteins accumulate late in pollen development and are not detectable in other parts of the plant. Although not present in unpollinated or self-pollinated styles, the 40-kilodalton to 45-kilodalton antigens are detectable in extracts from cross-pollinated styles, suggesting that the proteins are present in pollen tubes growing through the style during pollination. The proteins are also present in pollen tubes growing in vitro. Both nucleotide and amino acid sequences are similar to the published sequences for cDNAs encoding the enzyme polygalacturonase, which suggests that the P2 gene family may function in depolymerizing pectin during pollen development, germination, and tube growth. Cross-hybridizing RNAs and immunoreactive proteins were detected in pollen from a wide variety of plant species, which indicates that the P2 family of polygalacturonase-like genes are conserved and may be expressed in the pollen from many angiosperms.
我们已经分离并鉴定了在月见草花粉中表达的一个基因家族（P2）的cDNA克隆。这个家族大约包含六到八个家族成员，并且仅在花粉中高水平表达。一个近乎全长的cDNA克隆所预测的蛋白质序列表明，这些基因的蛋白质产物至少为38,000道尔顿。我们通过使用针对β-半乳糖苷酶/花粉cDNA融合蛋白的抗体，鉴定了这个家族中一个cDNA所编码的蛋白质。使用这些抗体进行的免疫印迹分析鉴定出了一个大约40千道尔顿的蛋白质家族，该家族存在于成熟花粉中，这表明这些mRNA并非仅仅在花粉萌发后才储存用于翻译。这些蛋白质在花粉发育后期积累，在植物的其他部位无法检测到。虽然在未授粉或自花授粉的花柱中不存在，但在异花授粉花柱的提取物中可检测到40千道尔顿至45千道尔顿的抗原，这表明这些蛋白质存在于授粉期间通过花柱生长的花粉管中。这些蛋白质也存在于体外生长的花粉管中。核苷酸和氨基酸序列均与已发表的编码多聚半乳糖醛酸酶的cDNA序列相似，这表明P2基因家族可能在花粉发育、萌发和花粉管生长过程中参与果胶的解聚作用。在多种植物物种的花粉中检测到了交叉杂交的RNA和免疫反应性蛋白质，这表明多聚半乳糖醛酸酶样基因的P2家族是保守的，可能在许多被子植物的花粉中表达。
