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Water and CO 2 permeability of SsAqpZ, the cyanobacterium Synechococcus sp. PCC7942 aquaporin
Author(s) -
Ding Xiaodong,
Matsumoto Tadashi,
Gena Patrizia,
Liu Chengwei,
PellegriniCalace Marialuisa,
Zhong Shihua,
Sun Xiaoli,
Zhu Yanming,
Katsuhara Maki,
Iwasaki Ikuko,
Kitagawa Yoshichika,
Calamita Giuseppe
Publication year - 2013
Publication title -
biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 85
eISSN - 1768-322X
pISSN - 0248-4900
DOI - 10.1111/boc.201200057
Subject(s) - biology , synechococcus , cyanobacteria , aquaporin , photosynthesis , mutant , biochemistry , osmotic pressure , intracellular , xenopus , osmotic shock , extracellular , microbiology and biotechnology , botany , bacteria , gene , genetics
Background information Cyanobacteria possess Aquaporin‐Z (AqpZ) membrane channels which have been suggested to mediate the water efflux underlying osmostress‐inducible gene expression and to be essential for glucose metabolism under photomixotrophic growth. However, preliminary observations suggest that the biophy‐sical properties of transport and physiological meaning of AqpZ in such photosynthetic microorganisms are not yet completely assessed. Results In this study, we used Xenopus laevis oocyte and proteoliposome systems to directly demonstrate the water permeability of the cyanobacterium Synechococcus sp. PCC7942 aquaporin, SsAqpZ. By an in vitro assay of intracellular acidification in yeast cells, SsAqpZ was found to transport also CO 2 . Consistent with this result, during the entire exponential phase of growth, Synechococcus SsAqpZ‐null‐mutant cells grew slower than the corresponding wild‐type cells. This phenotype was stronger with higher levels of extracellular CO 2 . In line with the conversion of CO 2 gas into HCO 3 − ions under alkaline conditions, the impairment in growth of the SsAqpZ‐null strain was weaker in more alkaline culture medium. Conclusions Cyanobacterial SsAqpZ may exert a pleiotropic function in addition to the already reported roles in macronutrient homeostasis and osmotic‐stress response as it appears to constitute an important pathway in CO 2 uptake, a fundamental step in photosynthesis.