Zhai Ying, Peng Hao, Neff Michael M, Pappu Hanu R
Department of Plant Pathology, Washington State University, Pullman, WA, United States.
Department of Crop and Soil Sciences, Washington State University, Pullman, WA, United States.
Front Plant Sci. 2019 Jun 28;10:804. doi: 10.3389/fpls.2019.00804. eCollection 2019.
Members of the virus order cause serious diseases in animals, humans and plants. Family in this order contains only one genus , and members in this genus exclusively infect plants. (TSWV) is considered one of the most economically important plants viruses. Little is known about the regulatory elements in the TSWV genome. Here we show that, when in the cDNA form, the 5'-upstream region of the TSWV-coded G/G gene (pG/G) possesses putative -regulatory elements, including an auxin responsive element (AuxRE) for binding of auxin response factors (ARFs), as well as a circadian clock-associated 1 (CCA1) protein binding site (CBS). Due to the lack of a reverse genetics system, we verified the functionality of these elements in Arabidopsis. pG/G showed light-suppressive promoter activity in transgenic Arabidopsis, and mutation in the CBS was sufficient to switch the activity to light inducible. Additionally, exogenous auxin treatments repressed the promoter activity of both wild type and CBS-mutated pG/G. Mutation in AuxRE in both promoters abolished their sensitivity to auxin. As transcriptional repressors, both CCA1 and ARF2 were able to bind to pG/G directly. To our knowledge, this is the first report that a 5'-terminal sequence of an RNA virus has light-and hormone-responsive promoter activities when expressed as cDNA in host plant's nuclear background. Our findings suggest new clues on the possible origin, evolution and function of the TSWV genomic sequence and its non-coding regions.
病毒目成员可在动物、人类和植物中引发严重疾病。该目中的 科仅包含一个属 ，此属成员专门感染植物。番茄斑萎病毒（TSWV）被认为是对经济影响最为重大的植物病毒之一。人们对TSWV基因组中的调控元件知之甚少。在此我们表明，当呈cDNA形式时，TSWV编码的G/G基因（pG/G）的5'上游区域具有假定的 调控元件，包括用于生长素反应因子（ARF）结合的生长素反应元件（AuxRE），以及一个生物钟关联1（CCA1）蛋白结合位点（CBS）。由于缺乏反向遗传学系统，我们在拟南芥中验证了这些元件的功能。pG/G在转基因拟南芥中表现出光抑制启动子活性，且CBS中的突变足以将活性转变为光诱导型。此外，外源生长素处理抑制了野生型和CBS突变型pG/G的启动子活性。两个启动子中AuxRE的突变消除了它们对生长素的敏感性。作为转录抑制因子，CCA1和ARF2都能够直接与pG/G结合。据我们所知，这是首份关于RNA病毒的5'末端序列在宿主植物核背景中以cDNA形式表达时具有光和激素响应启动子活性的报告。我们的发现为TSWV基因组序列及其非编码区的可能起源、进化和功能提供了新线索。
