Key Laboratory of Soybean Molecular Design Breeding, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China.
Key Laboratory of Molecular Epigenetics of MOE, Institute of Genetics and Cytology, Northeast Normal University, Changchun, China.
BMC Plant Biol. 2021 May 25;21(1):234. doi: 10.1186/s12870-021-03035-0.
Trichome initiation in Arabidopsis is regulated by a MYB-bHLH-WD40 (MBW) transcriptional activator complex formed by the R2R3 MYB transcription factor GLABRA1 (GL1), MYB23 or MYB82, the bHLH transcription factor GLABRA3 (GL3), ENHANCER OF GLABRA3 (EGL3) or TRANSPARENT TESTA8 (TT8), and the WD40-repeat protein TRANSPARENT TESTA GLABRA1 (TTG1). However, the functions of the rice homologs of the MBW complex proteins remained uncharacterized.
Based on amino acid sequence identity and similarity, and protein interaction prediction, we identified OsGL1s, OsGL3s and OsTTG1s as rice homologs of the MBW complex proteins. By using protoplast transfection, we show that OsGL1D, OsGL1E, OsGL3B and OsTTG1A were predominantly localized in the nucleus, OsGL3B functions as a transcriptional activator and is able to interact with GL1 and TTG1. By using yeast two-hybrid and protoplast transfection assays, we show that OsGL3B is able to interact with OsGL1E and OsTTG1A, and OsGL1E and OsTTG1A are also able to interact with GL3. On the other hand, we found that OsGL1D functions as a transcription activator, and it can interact with GL3 but not OsGL3B. Furthermore, our results show that expression of OsTTG1A in the ttg1 mutant restored the phenotypes including alternations in trichome and root hair formation, seed color, mucilage production and anthocyanin biosynthesis, indicating that OsTTG1A and TTG1 may have similar functions.
These results suggest that the rice homologs of the Arabidopsis MBW complex proteins are able to form MBW complexes, but may have conserved and non-conserved functions.
拟南芥毛状体的起始由一个由 R2R3 MYB 转录因子 GLABRA1（GL1）、MYB23 或 MYB82、bHLH 转录因子 GLABRA3（GL3）、ENHANCER OF GLABRA3（EGL3）或 TRANSPARENT TESTA8（TT8）和 WD40 重复蛋白 TRANSPARENT TESTA GLABRA1（TTG1）组成的 MYB-bHLH-WD40（MBW）转录激活复合物调控。然而，水稻 MBW 复合物蛋白同源物的功能仍未被阐明。
基于氨基酸序列的同一性和相似性以及蛋白质相互作用预测，我们鉴定出 OsGL1s、OsGL3s 和 OsTTG1s 是水稻 MBW 复合物蛋白的同源物。通过使用原生质体转染，我们表明 OsGL1D、OsGL1E、OsGL3B 和 OsTTG1A 主要定位于细胞核中，OsGL3B 作为转录激活因子起作用，并且能够与 GL1 和 TTG1 相互作用。通过酵母双杂交和原生质体转染实验，我们表明 OsGL3B 能够与 OsGL1E 和 OsTTG1A 相互作用，并且 OsGL1E 和 OsTTG1A 也能够与 GL3 相互作用。另一方面，我们发现 OsGL1D 作为转录激活因子起作用，它可以与 GL3 相互作用，但不能与 OsGL3B 相互作用。此外，我们的结果表明，在 ttg1 突变体中表达 OsTTG1A 恢复了包括毛状体和根毛形成、种子颜色、黏液产生和花青素生物合成在内的表型，表明 OsTTG1A 和 TTG1 可能具有相似的功能。
这些结果表明，拟南芥 MBW 复合物蛋白的水稻同源物能够形成 MBW 复合物，但可能具有保守和非保守的功能。
