Conjugation of R27 plasmid is thermoregulated, being promoted at 25°C and repressed at 37°C. Previous studies identified plasmid-encoded regulators, HtdA, TrhR and TrhY, that control expression of conjugation-related genes (tra). Moreover, the nucleoid-associated protein H-NS represses conjugation at non-permissive temperature. A transcriptomic approach has been used to characterize the effect of temperature on the expression of the 205 R27 genes. Many of the 35 tra genes, directly involved in plasmid-conjugation, were upregulated at 25°C. However, the majority of the non-tra R27 genes—many of them with unknown function—were more actively expressed at 37°C. The role of HtdA, a regulator that causes repression of the R27 conjugation by counteracting TrhR/TrhY mediated activation of tra genes, has been investigated. Most of the R27 genes are severely derepressed at 25°C in an htdA mutant, suggesting that HtdA is involved also in the repression of R27 genes other than the tra genes. Interestingly, the effect of htdA mutation was abolished at non-permissive temperature, indicating that the HtdA-TrhR/TrhY regulatory circuit mediates the environmental regulation of R27 gene expression. The role of H-NS in the proposed model is discussed.

R27 质粒的结合是温度调节的，在 25°C 时被促进，在 37°C 时被抑制。以前的研究确定了质粒编码的调节因子，HtdA、TrhR 和 TrhY，它们控制结合相关基因的表达。特拉）。此外，类核相关蛋白 H-NS 在不允许的温度下抑制结合。转录组学方法已用于表征温度对 205 R27 基因表达的影响。许多 35特拉直接参与质粒结合的基因在 25°C 时上调。然而，大多数非特拉R27 基因——其中许多功能未知——在 37°C 时表达更为活跃。HtdA 的作用，一种通过抵消 TrhR/TrhY 介导的特拉基因，已经研究过了。大多数 R27 基因在 25°C 时被严重去抑制HTDA突变体，表明 HtdA 还参与抑制 R27 基因，而不是特拉基因。有趣的是，效果HTDA突变在非允许温度下被消除，表明 HtdA-TrhR/TrhY 调节回路介导 R27 基因表达的环境调节。讨论了 H-NS 在所提出的模型中的作用。