Transcriptional shift and metabolic adaptations during Leishmania quiescence using stationary-phase and drug pressure as models

Microorganisms can adopt a quiescent physiological condition which acts as a survival strategy under unfavourable conditions. Quiescent cells are characterized by slow or non-proliferation and deep down-regulation of processes related to biosynthesis. Although quiescence has been described mostly in bacteria, this survival skill is widespread, including in eukaryotic microorganisms. In Leishmania, a digenetic parasitic protozoan that causes a major infectious disease, quiescence has been demonstrated, but molecular and metabolic features enabling its maintenance are unknown. Here we quantified the transcriptome and metabolome of Leishmania promastigotes and amastigotes where quiescence was induced in vitro either through drug pressure or by stationary phase. Quiescent cells have a global and coordinated reduction in overall transcription, with levels dropping to as low as 0.4% of those in proliferating cells. However, a subset of transcripts did not follow this trend and were relatively upregulated in quiescent populations, including those encoding membrane components such as amastins and GP63 or processes like autophagy. The metabolome followed a similar trend of overall downregulation albeit to a lesser magnitude than the transcriptome. Noteworthy, among the commonly upregulated metabolites were those involved in carbon sources as an alternative to glucose. This first integrated two omics layers affords novel insights into cell regulation and shows commonly modulated features across stimuli and stages.