Sawano Hikaru, Matsuzaki Takuma, Usui Tomoyuki, Tabara Midori, Fukudome Akihito, Kanaya Akihiro, Tanoue Daichi, Hiraguri Akihiro, Horiguchi Gorou, Ohtani Misato, Demura Taku, Kozaki Toshinori, Ishii Kazuo, Moriyama Hiromitsu, Fukuhara Toshiyuki
Departments of Applied Biological Sciences, Tokyo University of Agriculture and Technology, 3-5-8 Saiwaicho, Fuchu, Tokyo, 183-8509, Japan.
Molecular and Environmental Plant Sciences, Department of Horticultural Sciences, Vegetable and Fruit Development Center, Texas A&M University, College Station, TX, 77843, USA.
J Plant Res. 2017 Jan;130(1):45-55. doi: 10.1007/s10265-016-0886-0. Epub 2016 Dec 19.
The model plant Arabidopsis thaliana has five double-stranded RNA-binding proteins (DRB1-DRB5), two of which, DRB1 and DRB4, are well characterized. In contrast, the functions of DRB2, DRB3 and DRB5 have yet to be elucidated. In this study, we tried to uncover their functions using drb mutants and DRB-over-expressed lines. In over-expressed lines of all five DRB genes, the over-expression of DRB2 or DRB3 (DRB2ox or DRB3ox) conferred a downward-curled leaf phenotype, but the expression profiles of ten small RNAs were similar to that of the wild-type (WT) plant. Phenotypes were examined in response to abiotic stresses. Both DRB2ox and DRB3ox plants exhibited salt-tolerance. When these plants were exposed to cold stress, drb2 and drb3 over-accumulated anthocyanin but DRB2ox and DRB3ox did not. Therefore, the over-expression of DRB2 or DRB3 had pleiotropic effects on host plants. Microarray and deep-sequencing analyses indicated that several genes encoding key enzymes for anthocyanin biosynthesis, including chalcone synthase (CHS), dihydroflavonol reductase (DFR) and anthocyanidin synthase (ANS), were down-regulated in DRB3ox plants. When DRB3ox was crossed with the pap1-D line, which is an activation-tagged transgenic line that over-expresses the key transcription factor PAP1 (Production of anthocyanin pigmentation1) for anthocyanin biosynthesis, over-expression of DRB3 suppressed the expression of PAP1, CHS, DFR and ANS genes. DRB3 negatively regulates anthocyanin biosynthesis by modulating the level of PAP1 transcript. Since two different small RNAs regulate PAP1 gene expression, a possible function of DRB3 for small RNA biogenesis is discussed.
模式植物拟南芥有五个双链RNA结合蛋白（DRB1 - DRB5），其中两个，DRB1和DRB4，已得到充分表征。相比之下，DRB2、DRB3和DRB5的功能尚未阐明。在本研究中，我们试图利用drb突变体和DRB过表达系来揭示它们的功能。在所有五个DRB基因的过表达系中，DRB2或DRB3（DRB2ox或DRB3ox）的过表达赋予叶片向下卷曲的表型，但十种小RNA的表达谱与野生型（WT）植物相似。检测了对非生物胁迫的响应表型。DRB2ox和DRB3ox植物均表现出耐盐性。当这些植物暴露于冷胁迫时，drb2和drb3中花青素过度积累，而DRB2ox和DRB3ox则没有。因此，DRB2或DRB3的过表达对宿主植物具有多效性作用。微阵列和深度测序分析表明，在DRB3ox植物中，几个编码花青素生物合成关键酶的基因，包括查尔酮合酶（CHS）、二氢黄酮醇还原酶（DFR）和花青素合酶（ANS），表达下调。当DRB3ox与pap1 - D系杂交时，pap1 - D系是一个激活标签转基因系，其过表达花青素生物合成的关键转录因子PAP1（花青素色素沉着1），DRB3的过表达抑制了PAP1、CHS、DFR和ANS基因的表达。DRB3通过调节PAP1转录本水平负调控花青素生物合成。由于两种不同的小RNA调节PAP1基因表达，因此讨论了DRB3在小RNA生物合成中的可能功能。
