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The LysR ‐type transcription factor PacR is a global regulator of photosynthetic carbon assimilation in A nabaena
Author(s) -
Picossi Silvia,
Flores Enrique,
Herrero Antonia
Publication year - 2015
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.12800
Subject(s) - rubisco , biology , photosynthesis , mutant , photosystem i , pyruvate carboxylase , biochemistry , operon , cyanobacteria , wild type , photosystem ii , botany , gene , genetics , bacteria , enzyme
Summary Cyanobacteria perform water‐splitting photosynthesis and are important primary producers impacting the carbon and nitrogen cycles at global scale. They fix CO 2 through ribulose‐bisphosphate carboxylase/oxygenase ( RuBisCo ) and have evolved a distinct CO 2 concentrating mechanism ( CCM ) that builds high CO 2 concentrations in the vicinity of RuBisCo favouring its carboxylase activity. Filamentous cyanobacteria such as A nabaena fix CO 2 in photosynthetic vegetative cells, which donate photosynthate to heterocysts that rely on a heterotrophic metabolism to fix N 2 . CCM elements are induced in response to inorganic carbon limitation, a cue that exposes the photosynthetic apparatus to photodamage by over‐reduction. An A nabaena mutant lacking the LysR ‐type transcription factor A ll3953 grew poorly and dies under high light. The rbcL operon encoding RuBisCo was induced upon carbon limitation in the wild type but not in the mutant. ChIP ‐ S eq analysis was used to globally identify A ll3953 targets under carbon limitation. Targets include, besides rbcL , genes encoding CCM elements, photorespiratory pathway‐ photosystem‐ and electron transport‐related components, and factors, including flavodiiron proteins, with a demonstrated or putative function in photoprotection. Quantitative reverse transcription polymerase chain reaction analysis of selected A ll3953 targets showed regulation in the wild type but not in the mutant. A ll3953 ( PacR ) is a global regulator of carbon assimilation in an oxygenic photoautotroph.