Laboratoire Génome et Développement des Plantes, Centre National de la Recherche Scientifique/Institut de Recherche pour le Développement/Université de Perpignan, Perpignan, France.
PLoS One. 2011 Feb 24;6(2):e17216. doi: 10.1371/journal.pone.0017216.
General transcription factor IIB (TFIIB) and TFIIB-related factor (BRF), are conserved RNA polymerase II/III (RNAPII/III) selectivity factors that are involved in polymerase recruitment and transcription initiation in eukaryotes. Recent findings have shown that plants have evolved a third type of B-factor, plant-specific TFIIB-related protein 1 (pBRP1), which seems to be involved in RNAPI transcription. Here, we extend the repertoire of B-factors in plants by reporting the characterization of a novel TFIIB-related protein, plant-specific TFIIB-related protein 2 (pBRP2), which is found to date only in the Brassicacea family. Unlike other B-factors that are ubiquitously expressed, PBRP2 expression is restricted to reproductive organs and seeds as shown by RT-PCR, immunofluorescence labelling and GUS staining experiments. Interestingly, pbrp2 loss-of-function specifically affects the development of the syncytial endosperm, with both parental contributions required for wild-type development. pBRP2, is the first B-factor to exhibit cell-specific expression and regulation in eukaryotes, and might play a role in enforcing bi-parental reproduction in angiosperms.
一般转录因子 IIB（TFIIB）和 TFIIB 相关因子（BRF）是保守的 RNA 聚合酶 II/III（RNAPII/III）选择性因子，参与真核生物的聚合酶募集和转录起始。最近的研究发现，植物已经进化出了第三种 B 因子，即植物特异性 TFIIB 相关蛋白 1（pBRP1），它似乎参与了 RNAPI 的转录。在这里，我们通过报道一种新型 TFIIB 相关蛋白植物特异性 TFIIB 相关蛋白 2（pBRP2）的特征来扩展植物 B 因子的范围，到目前为止，这种蛋白仅在十字花科中发现。与其他普遍表达的 B 因子不同，如 RT-PCR、免疫荧光标记和 GUS 染色实验所示，PBRP2 的表达仅限于生殖器官和种子。有趣的是，pbrp2 功能丧失特异性地影响合胞胚乳的发育，野生型发育需要双亲的共同作用。pBRP2 是第一个在真核生物中表现出细胞特异性表达和调控的 B 因子，可能在被子植物中发挥作用，以强制执行双亲繁殖。
