TY - JOUR T1 - The two-component response regulator OrrA confers dehydration tolerance by regulating <em>anaKa</em> expression in the cyanobacterium <em>Anabaena</em> sp. strain PCC 7120 JF - bioRxiv DO - 10.1101/2021.08.03.454875 SP - 2021.08.03.454875 AU - Satoshi Kimura AU - Miho Sato AU - Xingyan Fan AU - Masayuki Ohmori AU - Shigeki Ehira Y1 - 2021/01/01 UR - http://biorxiv.org/content/early/2021/08/03/2021.08.03.454875.abstract N2 - The aquatic cyanobacterium Anabaena sp. strain PCC 7120 exhibits dehydration tolerance. The regulation of gene expression in response to dehydration is crucial for the acquisition of dehydration tolerance, but the molecular mechanisms underlying dehydration responses remain unknown. In this study, the functions of the response regulator OrrA in the regulation of salt and dehydration responses were investigated. Disruption of orrA abolished or diminished the induction of hundreds of genes in response to salt stress and dehydration. Thus, OrrA is a principal regulator of both stress responses. In particular, OrrA plays a crucial role in dehydration tolerance because an orrA disruptant completely lost the ability to regrow after dehydration. Moreover, in the OrrA regulon, anaKa encoding a protein of unknown function was revealed to be indispensable for dehydration tolerance. OrrA and AnaK are conserved among the terrestrial cyanobacteria, suggesting their conserved functions in dehydration tolerance in cyanobacteria.Competing Interest StatementThe authors have declared no competing interest. ER -