Diversity of the structures and functions of Streptomyces linear genomes

(1)我们发现，在灰色链霉菌402-2中发现的染色体倒位是通过一个转座子的转座以及新旧转座子之间的同源重组发生的，因此，我们在菌株402-2中鉴定了两个转座子两端的嵌合直接重复序列。(2)我们发现，在S.通过扩增包含SCP 1中的SCP 1和SCP 2片段的36-kb DNA单位形成紫红JCM 4979。非常有趣的是，这些线性质粒是相容的，尽管它们具有相同的oriC序列。(3)通过对S. Rochefindicate酰胺中间体氧化成酰亚胺，然后被C2亲核攻击，形成了兰卡菌素独特的17元环。Ikc簇在S.蓝绿烷和lkcFG基因融合实验支持我们对lankacidin的模块迭代聚酮生物合成假说。(4)饲养和基因打靶实验表明，异亮氨酸被氧化为2-甲基丁酸，并纳入到8，15-didexylankanaline骨架，然后在15和8位分别由LkmK和LkmF羟基化。(5)我们发现srrX-srrA在S.罗切。srrX基因对抗生素的产生有正效应，对孢子的形成有负效应，而srrA基因则逆转了srrX基因的这两种效应。广泛的转录分析证实了从srrX通过srrA到srrY的信号通路。我们还确定了两个SrrA结合位点的srrY基因，其中包含一个回文序列GB-受体和SARP蛋白的重复序列，分别上游。

(1) We revealed that the chromosomal inversion found in Streptomycesgriseus 402-2 occurred by transposition of a transposonfollowedbyhomologousrecombinationbetweenthe old and new transposons.Consequently, we identified chimeric direct repeat sequences at both ends of the two transposons in strain 402-2.(2) We revealed that a series of linear plasmids in S. violaceoruber JCM4979 were formed by amplification of a 36-kb DNA unit comprising of SCP1 and SCP2 fragments in SCP1. It is quite interesting that these linear plasmids are compatible in spite of their identical oriC sequence.(3) The structure of LC-KA05 produced by an amine oxidasemutantof S. rochefindicated that oxidation of an amide intermediate to an imide followed by nucleophilic attack by C2 formed the unique 17-membered ring of lankacidin. Heterologous expression of the Ikc cluster in S. lividans and the lkcFG gene fusion experiment supported our modular-iterative polyketide biosynthesis hypothesis for lankacidin.(4) Feeding and gene targeting experiments revealed that isoleucine was oxidized to 2-methylbutyrate and incorporated into the 8,15-didexylankanolide skeleton, and then hydroxylated at the 15 and 8 positions by LkmK and LkmF, respectively.(5) We revealed that srrX-srrA make a y-butyrolactone-receptor system in S. rochei. The srrX gene showed a positive effect on antibiotic production and a negative effect on spore formation, while, srrA reversed both effects of srrX. Extensive transcriptional analysis confirmed the signaling pathway from srrX through srrA to srrY. We also identified two SrrA binding sites upstream of the srrY gene, which contained a palindromic sequence for GB-receptors and repeat sequences for SARP proteins, respectively.