Genes regulated by branched-chain polyamine in the hyperthermophilic archaeon Thermococcus kodakarensis

Branched-chain polyamine (BCPA) synthase (BpsA), encoded by the bpsA gene, is responsible for the biosynthesis of BCPA in the hyperthermophilic archaeon Thermococcus kodakarensis, which produces N⁴-bis(aminopropyl)spermidine and spermidine. Here, next-generation DNA sequencing and liquid chromatography-mass spectrometry (LC-MS) were used to perform transcriptomic and proteomic analyses of a T. kodakarensis strain (DBP1) lacking bpsA. Subsequently, the contributions of BCPA to gene transcription (or transcript stabilization) and translation (or protein stabilization) were analyzed. Compared with those in the wild-type strain (KU216) cultivated at 90 °C, the transcript levels of 424 and 21 genes were up- and downregulated in the DBP1 strain, respectively. The expression levels of 12 frequently-used tRNAs were lower in DBP1 cells than KU216 cells, suggesting that BCPA affects translation efficiency in T. kodakarensis. LC-MS analyses of cells grown at 90 °C detected 50 proteins in KU216 cells only, 109 proteins in DBP1 cells only, and 499 proteins in both strains. Notably, the transcript levels of some genes did not correlate with those of the proteins. RNA-seq and RT-qPCR analyses of ten proteins that were detected in KU216 cells only, including three flagellin-related proteins (FlaB2-4) and cytosolic NiFe-hydrogenase subunit alpha (HyhL), revealed that the corresponding transcripts were expressed at higher levels in DBP1 cells than KU216 cells. Electron microscopy analyses showed that flagella formation was disrupted in DBP1 cells at 90 °C, and western blotting confirmed that HyhL expression was eliminated in the DBP1 strain. These results suggest that BCPA plays a regulatory role in gene expression in T. kodakarensis.