Bitra Kavita, Tan Anjiang, Dowling Ashley, Palli Subba R
Department of Entomology, College of Agriculture, University of Kentucky, Lexington, KY 40546, USA.
Gene. 2009 Dec 1;448(1):74-87. doi: 10.1016/j.gene.2009.08.003. Epub 2009 Aug 13.
The basic helix-loop-helix transcription factors are present in animals, plants and fungi and play important roles in the control of cellular proliferation, tissue differentiation, development and detoxification. Although insect genomes contain more than 50 helix-loop-helix transcription factors, the functions of only a few are known. RNAi has become a widely used tool to knock-down the expression to analyze the function of genes. As RNAi works well in Tribolium castaneum, we utilized this insect and RNAi to determine functions of 19 bHLH transcription factors belonging to PAS and HES families during the larval stages of the red flour beetle, T. castaneum. We searched the genome sequence of T. castaneum and identified 53 bHLH genes. Phylogenetic analyses classified these 53 genes into ten families; PAS, HES, Myc/USF, Hand, Mesp, Shout, p48, NeuroD/Neurogenin, Atonal and AS-C. In RNAi studies, knocking-down the expression of seven members of the PAS and HES families affected the growth and development of T. castaneum. An inability to grow to reach critical weight to undergo metamorphosis, failure to complete larval-pupal or pupal-adult ecdysis and abnormal wing development are among the most common phenotypes observed in RNAi insects. Among the bHLH transcription factors studied, the steroid receptor coactivator (SRC) showed the most severe phenotypes. Knock-down in the expression of the gene coding for SRC caused growth arrest by affecting the regulation of lipid metabolism. These studies demonstrate the power of RNAi for functional characterization of members of the multigene families in this model insect.
基本螺旋-环-螺旋转录因子存在于动物、植物和真菌中，在细胞增殖、组织分化、发育及解毒控制中发挥重要作用。尽管昆虫基因组含有50多个螺旋-环-螺旋转录因子，但只有少数因子的功能是已知的。RNA干扰已成为一种广泛用于敲低基因表达以分析基因功能的工具。由于RNA干扰在赤拟谷盗中效果良好，我们利用这种昆虫和RNA干扰来确定属于PAS和HES家族的19个bHLH转录因子在赤拟谷盗幼虫阶段的功能。我们搜索了赤拟谷盗的基因组序列并鉴定出53个bHLH基因。系统发育分析将这53个基因分为十个家族；PAS、HES、Myc/USF、Hand、Mesp、Shout、p48、NeuroD/Neurogenin、无调蛋白和AS-C。在RNA干扰研究中，敲低PAS和HES家族七个成员的表达影响了赤拟谷盗的生长和发育。无法生长到达到变态所需的临界体重、未能完成幼虫-蛹或蛹-成虫蜕皮以及翅发育异常是在RNA干扰昆虫中观察到的最常见表型。在所研究的bHLH转录因子中，类固醇受体辅激活因子（SRC）表现出最严重的表型。编码SRC的基因表达敲低通过影响脂质代谢调节导致生长停滞。这些研究证明了RNA干扰在该模式昆虫中对多基因家族成员进行功能表征的作用。
