Differential expression of members of a cyanobacterial psbA gene family in response to light

Abstract

The genome of the cyanobacterium Synechococcus sp. strain PCC 7942 contains three psbA genes encoding two forms of the Dl protein: form I, the product of psbAI, differs from form II, the product of both psbAII and psbAIII, at 25 of 360 residues. DI is essential for photosynthesis as a core component of the photosystem II reaction center. Translational gene fusions between each of the Synechococcus psbA genes and the Escherichia coli lacZ gene were inserted into the chromosome of wild-type Synechococcus sp. at the respective psbA loci to serve as in vivo reporters of psbA expression. ji-Galactosidase activities indicated differential expression of the psbA-lacZ gene fusions related to light availability. Expression of psbAI was 500-fold greater than expression of psbAII and 50-fold greater than psbAIII under similar conditions. As light intensity decreased from 600 ,uE-m2 s'-to 2 ,uE. m-2 s , expression of the psbAI reporter increased eightfold while expression of the psbAlI and psbAIII reporters decreased 10-fold, suggesting differential production of the two forms of Dl in photosystem II in response to light availability. Relative levels of psbA-1acZ fusion transcripts directly reflected I-galactosidase activities in the transformants, although the fusion transcripts were less stable than native psbA messages.

In situ dynamics of O2, pH and cyanobacterial transcripts associated with CCM, photosynthesis and detoxification of ROS

“…In 2005, the lowest psbA1 transcript levels were observed during the highlight mid-day periods, whereas highest levels were observed under low irradiance in the late afternoon to early evening and in the early morning (Figure 5b). Our in situ results are consistent with culture studies of Syn OS-B 0 , where psbA2/3 transcript levels increased during the transition from low-to-high light, whereas psbA1 transcript levels increased when the cells were shifted from high-to-low light (Kilian et al, 2007); similar results were reported for other cultivated cyanobacteria (Schaefer and Golden, 1989).…”

Ribulose bisphosphate carboxylase gene expression in subtropical marine phytoplankton populations

“…Transcription of psbA, encoding the D1 protein of PS I1 in Synechococcus sp., occurs during periods of illumination (Schaffer & Golden 1989). Similarly, the chlorophyll binding protein, cab, mRNA levels are elevated during the dark period in Dunaliella sp.…”

Multiplication of antenna genes as a major adaptation to low light in a marine prokaryote

“…One intriguing question that remains to be solved is whether the multiple pcb gene copies are expressed differentially depending on the light conditions, as was previously shown for the different copies of psbA (17) and psbD (18) …”