青蒿植物内生链霉菌中的质粒pCQ4与噬菌体ΦCQ4

Plasmid pCQ4 and its phage ФCQ4 of endophytic Streptomyces sp．from Artemisia annua L．

摘要:

摘要:【目的】在青蒿植物的内生链霉菌W75 中检测到一个大的环型质粒pCQ4。克隆、测序、分析和功能研究pCQ4。【方法】Southern 杂交确定质粒的酶切图谱，利用接合转移和同源重组方法将质粒克隆到了大肠杆菌BAC 衍生的载体上，并进行鸟枪测序和分析。【结果】获得了全长为84833 bp的pCQ4 序列，预测编码129个基因，其中成簇的40 个基因与其它噬菌体的基因同源。实验证明含有质粒pCQ4 的菌株能够低频率释放噬菌体ФCQ4，并可以侵染消除了pCQ4 的W75X 孢子和形成噬菌斑。在透射电镜下观察到噬菌体颗粒，脉冲场凝胶电泳显示ФCQ4 为线型DNA。pCQ4 与已发表的链霉菌质粒-噬菌体pZL12比对，编码噬菌体的主要结构蛋白的基因是相似的。【结论】链霉菌大的质粒pCQ4 也可以转化为噬菌体ФCQ4，其噬菌体相关的基因簇可能是可转移的单元。

Abstract:

Abstract:［Objective］Large plasmid pCQ4 was detected in Streptomyces sp． W75 from Artemisia annua L． We clonined，sequenced，analyzed and characterized pCQ4． ［Methods］Southern hybridization was used to determine restriction map of pCQ4． To clone the full-length of pCQ4，conjugation and recombinational cloning in a BAC vector were used．［Results］ The complete nucleotide sequence of pCQ4 consisted of 84833-bp，encoding 129 ORFs which 40 ORFs resembled these of bacterial phages．W75 culture could infect W75 cured of pCQ4 and formed plaques on plate．Phage particle (ФCQ4) was observed by transmission electron microscopy． LinearФCQ4 DNA was detected on pulsed-field gel electrophoresis． Comparison to Streptomyces plasmid-phage pZL12，genes encoding major phage structural proteins resembled that of pCQ4．［Conclusion］Streptomyces plasmid pCQ4 could be transformed into lytic phageФCQ4，and the phage segment on pCQ4 might be a mobile unit．