Diversity of KaiC-based timing systems in marine Cyanobacteria

Abstract

The coordination of biological activities into daily cycles provides an important advantage for the fitness of diverse organisms. Most eukaryotes possess an internal clock ticking with a periodicity of about one day to anticipate sunrise and sunset. The 24-hour period of the free-running rhythm is highly robust against many changes in the natural environment. Among prokaryotes, only Cyanobacteria are known to harbor such a circadian clock. Its core oscillator consists of just three proteins, KaiA, KaiB, and KaiC that produce 24-hour oscillations of KaiC phosphorylation, even in vitro. This unique three-protein oscillator is well documented for the freshwater cyanobacterium Synechococcus elongatus PCC 7942. Several physiological studies demonstrate a circadian clock also for other Cyanobacteria including marine species. Genes for the core clock components are present in nearly all marine cyanobacterial species, though there are large differences in the specific composition of these genes. In the first section of this review we summarize data on the model circadian clock from S. elongatus PCC 7942 and compare it to the reduced clock system of the marine cyanobacterium Prochlorococcus marinus MED4. In the second part we discuss the diversity of timing mechanisms in other marine Cyanobacteria with regard to the presence or absence of different components of the clock.

Daily Expression Pattern of Protein-Encoding Genes and Small Noncoding RNAs in Synechocystis sp. Strain PCC 6803

“…In this study, the amount of as_flv4 rose rapidly as soon as the light was turned on, whereas the abundance of flv4 target mRNA was anticorrelated with this rise, indicating a negative role of as_flv4 in flv4 mRNA stability. The sasA gene (also called hik8, sarA, or sll0750) encodes the histidine kinase SasA, which very likely plays a key role in gene expression regulation in Synechocystis (50). In this study, the amount of the antisense RNA as_SasA was enhanced during the light phase and correlated marginally with the amount of sasA mRNA (Fig.…”

Proposed Role for KaiC-Like ATPases as Major Signal Transduction Hubs in Archaea

“…One of the archaeal proteins, namely, the SSO2452 protein of Sulfolobus solfataricus, has been experimentally studied in this context and was shown not to be an active recombinase but could bind single-stranded DNA and inhibit D-loop formation by RadA (22). However, outside the Archaea, the best-studied protein in this family is the cyanobacterial circadian clock ATPase KaiC, which does not appear to be involved in DNA recombination (23,24).…”

Proteomic analysis of post translational modifications in cyanobacteria

“…PTMs participate in numerous biological processes in cyanobacteria, such as circadian rhythms [29,30], global carbon/nitrogen control [31], nitrogen fixation [32], complementary chromatic adaptation [33,34]. PTM events are also reported to exist in photosynthesis apparatus, including photosystem I [35], photosystem II [36], phycobiliproteins [37,38] and cytochrome b6f complex [39].…”

“…Another example is the phosphorylation of phycobiliproteins and phycobilisome linker proteins [9,67]. KaiC, a central clock protein in cyanobacteria, was also reported to undergo circadian oscillations through autocatalytic phosphorylation/ de-phosphorylation cycle (reviewed by Williams, 2007& Axmann, 2014 [29,30].…”