Polycyclic tetramate macrolactams (PTMs) are a widely distributed class of structurally complex natural products, and most of them exhibit multiple biological activities. However, the transcriptional regulators ( TRs) involved in the regulation of PTM production have seldom been reported. Here, we identified three TRs, i.e., Sxim_22880, CvnABC(Sx), and WblA(Sx), and revealed their positive roles in the regulation of PTM biosynthesis in mangrove-derived Streptomyces xiamenensis 318. This strain produces a considerable amount of PTMs at 30 degrees C, but the production of PTMs is mostly blocked at 37 degrees C. Quantitative real-time PCR analysis confirmed that the transcriptions of PTM biosynthetic genes were downregulated. We determined that the transcriptions of several putative TRs, i.e., WblA(Sx), Sxim_22880, and CvnC(Sx), were significantly downregulated under such heat-shock conditions. We showed that the transcription of PTM biosynthetic genes and the production of PTMs could be restored at 37 degrees C if the impaired transcriptions of wblA(Sx), sxim_22880, and cvnABC(Sx) were restored. Electrophoretic mobility shift assays showed that none of these TRs could bind to the promoter region of the PTM gene cluster, suggesting their indirect but positive involvement in the regulation on PTM production. Moreover, concurrent overexpression of the three TRs in S. xiamenensis 318 resulted in a 242.5% increase in PTM production when the strain was cultured at 30 degrees C. Furthermore, overexpression of these three TRs in Streptomyces sp. FR-008 and S. albus J1074 stimulated the production of new secondary metabolites, indicating that these conserved TRs could be used to activate cryptic secondary metabolite gene clusters in Streptomyces.