, 2012 and Zinser et al., 2009), protein accumulation ( Waldbauer et al., 2012), cell cycling (e.g. Bruyant et al., 2001, Holtzendorff et al., 2001, Holtzendorff et

al., 2008, Liu et al., 1997, Partensky et al., 1996, Vaulot et al., 1995 and Vaulot and Marie, 1999), amino acid uptake ( Mary et al., 2008) as well as carbon fixation and other photosynthetic parameters ( Bruyant and Babin, 2005, Claustre et al., 2002 and Zinser et al., 2009) have been reported. Omic analyses of MED4 revealed that the diel gene expression patterns hold true for nearly the entire transcriptome and proteome ( Waldbauer et al., 2012 and Zinser et al., 2009). For most of the periodic genes RNA accumulation peaked around dawn or dusk. Transcript maxima of at least few genes were

distributed http://www.selleckchem.com/products/Adriamycin.html over the complete day ( Waldbauer et al., 2012 and Zinser et al., 2009). Maximal abundance of the majority of oscillating proteins peaked between 2 and 8 h after their respective mRNAs ( Waldbauer et al., 2012). However, a high divergence of transcript–protein relationships regarding timing and magnitude of expression was observed. The kaiB and kaiC genes of MED4 exhibit periodic expression during the day–night cycle as observed in S. elongatus. Moreover, they appear to possess only one transcription initiation Navitoclax research buy start site upstream of kaiB, which would lead to a dicistronic mRNA like in S. elongatus as well. However, unequivocal evidence is still lacking ( Holtzendorff et al., 2008 and Vogel et al., 2003). In fact, transcription analyses have shown different results so far. While kaiB and kaiC peak in phase in one study (in late night) ( Holtzendorff et al., 2008), Zinser et al. (2009) showed that kaiC peaks around sunset. The reason for this difference (e.g. experimental setup) remains to be solved. Expression profiles of several genes peaking in the dark phase suggest anticipation of light changes, which would indicate an internal timing mechanism (Holtzendorff et al., 2008 and Zinser et al., 2009). However, MED4

does not exhibit find more self-sustained oscillations: When cells are shifted from light–dark cycles to constant light, cell cycle and psbA expression rhythms vanish. Therefore, it was suggested that MED4 harbors a core oscillatory mechanism that requires a daily resetting by environmental stimuli ( Holtzendorff et al., 2008). Biochemical analysis provided first evidence that the core of the hourglass-like timing mechanism in MED4 might be constituted by the remaining Kai proteins ( Axmann et al., 2009): KaiC from MED4, which shows 75% sequence identity to S. elongatus-KaiC, was proven to be an autokinase and ATPase in vitro. Thus MED4-KaiC displays at least two of the key enzymatic activities described for the well-studied S. elongatus counterpart. Intrinsic phosphorylation of the residues S427 and T428 (aligning with the known phosphorylation sites of S. elongatus-KaiC, see Fig. 2) occurred at high level and independently of S. elongatus-KaiA or MED4-KaiB.