Zhang J, Schairer H U, Schnetter W, Lereclus D, Agaisse H
Zentrum für Molekularbiologie Heidelberg and Zoologisches Institut, Universität Heidelberg, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
Nucleic Acids Res. 1998 Mar 1;26(5):1288-93. doi: 10.1093/nar/26.5.1288.
Bacillus popilliae is an obligate pathogen for larvae of the insect family Scarabaeidae (Coleoptera). It forms parasporal crystals upon sporulation. The gene cry18Aa coding for the parasporal crystal protein and an upstream open reading frame, orf1, were previously isolated from B.popilliae. Here we report an analysis of cry18Aa transcription in Bacillus thuringiensis. The only transcriptional start site of cry18Aa was found 29 bp upstream of the open reading frame orf1, suggesting that orf1 and cry18Aa are transcribed as an operon. lacZ fusion to the cry18Aa promoter was used to follow the time-course of cry18Aa transcription in wild type B.thuringiensis and in various B.thuringiensis sporulation-deficient mutants (spo0A, sigE or sigK). In wild type B.thuringiensis, the cry18Aa promoter was activated 2 h after the end of exponential growth and the expression lasted to the late sporulation phase. The results of promoter activity in Spo+or Spo-backgrounds together with the results of primer extension experiments suggest that the transcription from this promoter can be driven by both sigmaE and sigmaK types of RNA polymerase at a single start site. The promoter region of cry18Aa operon fits the consensus sequences of both sigmaE and sigmaK dependent promoters of Bacillus.
日本金龟子芽孢杆菌是金龟子科（鞘翅目）昆虫幼虫的专性病原体。它在孢子形成时形成伴胞晶体。之前已从日本金龟子芽孢杆菌中分离出编码伴胞晶体蛋白的cry18Aa基因和一个上游开放阅读框orf1。在此，我们报告了苏云金芽孢杆菌中cry18Aa转录的分析情况。cry18Aa唯一的转录起始位点位于开放阅读框orf1上游29 bp处，这表明orf1和cry18Aa作为一个操纵子进行转录。将lacZ与cry18Aa启动子融合，用于追踪cry18Aa在野生型苏云金芽孢杆菌以及各种苏云金芽孢杆菌孢子形成缺陷型突变体（spo0A、sigE或sigK）中转录的时间进程。在野生型苏云金芽孢杆菌中，cry18Aa启动子在指数生长末期结束后2小时被激活，且表达持续到孢子形成后期。Spo +或Spo -背景下的启动子活性结果以及引物延伸实验结果表明，该启动子的转录可由σE和σK两种类型的RNA聚合酶在单个起始位点驱动。cry18Aa操纵子的启动子区域符合芽孢杆菌σE和σK依赖性启动子的共有序列。
