AUTHOR=Sato Norihiro , Endo Mizuki , Nishi Hiroki , Fujiwara Shoko , Tsuzuki Mikio 

TITLE=Polyphosphate-kinase-1 dependent polyphosphate hyperaccumulation for acclimation to nutrient loss in the cyanobacterium, Synechocystis sp. PCC 6803

JOURNAL=Frontiers in Plant Science

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2024.1441626

DOI=10.3389/fpls.2024.1441626

ISSN=1664-462X

ABSTRACT=<p>Polyphosphate is prevalent in living organisms. To obtain insights into polyphosphate synthesis and its physiological significance in cyanobacteria, we characterize <italic>sll0290</italic>, a homolog of the polyphosphate-kinase-1 gene, in the freshwater cyanobacterium <italic>Synechocystis</italic> sp. PCC 6803. The Sll0290 protein structure reveals characteristics of Ppk1. A <italic>Synechocystis sll0290</italic> disruptant and <italic>sll0290</italic>-overexpressing <italic>Escherichia coli</italic> transformant demonstrated loss and gain of polyphosphate synthesis ability, respectively. Accordingly, <italic>sll0290</italic> is identified as <italic>ppk1</italic>. The disruptant (Δ<italic>ppk1</italic>) grows normally with aeration of ordinary air (0.04% CO<sub>2</sub>), consistent with its photosynthesis comparable to the wild type level, which contrasts with a previously reported high-CO<sub>2</sub> (5%) requirement for Δ<italic>ppk1</italic> in an alkaline hot spring cyanobacterium, <italic>Synechococcus</italic> OS-B’. <italic>Synechocystis</italic> Δ<italic>ppk1</italic> is defective in polyphosphate hyperaccumulation and survival competence at the stationary phase, and also under sulfur-starvation conditions, implying that sulfur limitation is one of the triggers to induce polyphosphate hyperaccumulation in stationary cells. Furthermore, Δ<italic>ppk1</italic> is defective in the enhancement of total phosphorus contents under sulfur-starvation conditions, a phenomenon that is only partially explained by polyphosphate hyperaccumulation. This study therefore demonstrates that in <italic>Synechocystis</italic>, <italic>ppk1</italic> is not essential for low-CO<sub>2</sub> acclimation but plays a crucial role in dynamic P-metabolic regulation, including polyP hyperaccumulation, to maintain physiological fitness under sulfur-starvation conditions.</p>