Pitt, Frances Diana, Mazard, Sophie, Humphreys, Lee and Scanlan, David J. . (2010) Functional characterization of synechocystis sp strain PCC 6803 pst1 and pst2 gene clusters reveals a novel strategy for phosphate uptake in a freshwater cyanobacterium. Journal of Bacteriology, Vol.192 (No.13). pp. 3512-3523. ISSN 0021-9193

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Abstract

Synechocystis sp. strain PCC 6803 possesses two putative ABC-type inorganic phosphate (P-i) transporters with three associated P-i-binding proteins (PBPs), SphX (encoded by sll0679), PstS1 (encoded by sll0680), and PstS2 (encoded by slr1247), organized in two spatially discrete gene clusters, pst1 and pst2. We used a combination of mutagenesis, gene expression, and radiotracer uptake analyses to functionally characterize the role of these PBPs and associated gene clusters. Quantitative PCR (qPCR) demonstrated that pstS1 was expressed at a high level in P-i-replete conditions compared to sphX or pstS2. However, a P-i stress shift increased expression of pstS2 318-fold after 48 h, compared to 43-fold for pstS1 and 37-fold for sphX. A shift to high-light conditions caused a transient increase of all PBPs, whereas N stress primarily increased expression of sphX. Interposon mutagenesis of each PBP demonstrated that disruption of pstS1 alone caused constitutive expression of pho regulon genes, implicating PstS1 as a major component of the P-i sensing machinery. The pstS1 mutant was also transformation incompetent. P-32(i) radiotracer uptake experiments using pst1 and pst2 deletion mutants showed that Pst1 acts as a low-affinity, high-velocity transporter (K-s, 3.7 +/- 0.7 mu M; V-max, 31.18 +/- 3.96 fmol cell(-1) min(-1)) and Pst2 acts as a high-affinity, low-velocity system (K-s, 0.07 +/- 0.01 mu M; V-max, 0.88 +/- 0.11 fmol cell(-1) min(-1)). These P-i ABC transporters thus exhibit differences in both kinetic and regulatory properties, the former trait potentially dramatically increasing the dynamic range of P-i transport into the cell, which has potential implications for our understanding of the ecological success of this key microbial group.

Item Type:	Journal Article
Subjects:	Q Science > QR Microbiology
Divisions:	Faculty of Science > Life Sciences (2010- ) > Biological Sciences ( -2010)
Journal or Publication Title:	Journal of Bacteriology
Publisher:	American Society for Microbiology
ISSN:	0021-9193
Date:	July 2010
Volume:	Vol.192
Number:	No.13
Number of Pages:	12
Page Range:	pp. 3512-3523
Identification Number:	10.1128/JB.00258-10
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	NERC
URI:	http://wrap.warwick.ac.uk/id/eprint/5684

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