An ATP-dependent bidirectional RNA helicase with RNA-dependent ATPase activity; does not unwind dsDNA, uses only (d)ATP (PubMed:15542859). Also has ATP-dependent RNA annealing activity; concurrent annealing and helicase activity promote strand-exchange activity (PubMed:15542859). In vitro has low helicase processivity, annealing processivity is probably higher (PubMed:15542859). Required for correct cold adaptation, probably by aiding translation of mRNAs required for photosynthesis and electron transport (PubMed:22575444). Probably regulates the cold-shock-inducible expression of the GroESL chaperones (PubMed:19926653). May partially regulate its own expression at both the transcriptional and post-transcriptional level (experiments used a construct expressing a 25 kDa trunacted protein which might have dominant-negative effects); is probably not directly involved in the pathway responsible for mRNA degradation (PubMed:23119089). ATP + H2O = ADP + H(+) + phosphate Helicase inhibited by the slowly-hydrolyzing ATP analog ATP-gamma-S (PubMed:15542859). Protein is rapidly degraded upon shifting from 20 to 30 degrees Celsius, the degradation machinery is only transiently present in cells grown at 30 degrees Celsius, is inhibited by commercial protease inhibitors and requires full-length protein expression (the N-terminal fragment does not induce proteolysis although it can be degraded by wild-type extract) (PubMed:24509313). A small amount is localized to the cell inner membrane and the thylakoid membrane, and cosediments with polysomes. Constitutively expressed; higher levels are found in light-grown cells and lower levels in dark cells unless grown in glucose (at protein level) (PubMed:11027719, PubMed:23119089). Transcript level is regulated by the redox state of the plastoquinone pool; transcript accumulates when electrons flow between PSII and cytochrome b6-f complex (reduction of the electron transport chain) (PubMed:11027719). LexA-like repressor probably represses its expression at least in part (PubMed:16840531). Induced by cold with maximal RNA induction at 15 degrees Celsius and maximal protein induction at 15-20 degrees Celsius (at protein level) (PubMed:23119089). Also expressed as part of the rimO-chrR operon; expression is greater at 20 than 30 degrees Celsius. The rimO-crhR transcript is processed between the 2 genes by RNase E (rne) (PubMed:32209657). Probably a complete knockout; no growth phenotype or large transcript changes at 34 degrees Celsius; at 24 degrees Celsius growth is considerably slower, while expression of a few genes is decreased (groES, groEL1, groEL2 and sll1611) or increased (pyrB, sll1911, sll1515 and rimO) (at 70 umol/photon/m(2)/s, 1% CO(2)) (PubMed:19926653, PubMed:32209657). At 24 degrees reduced chlorophyll and phycocyanin content and a gradual reduction in photosynthetic O(2) evolution; cells are locked in state 1 and unable to undergo state transitions, the plastoquinone pool is oxidized, leading to down-regulation of psaA and psaB transcripts and thus decreased PSI levels (PubMed:22575444). A partial knockout allowing expression of the first 224 residues as a 25 kDa truncated protein at 30 degrees Celsius has reduced growth, 20% reduced O(2) evolution and 10% reduced electron transport, at 20 degrees Celsius has similar, more severe effects; no growth with rapid loss of viability, little to no photosynthetic O(2) evolution, 50% reduced electron transport, decreased pigment content, smaller cell size and considerable intracellular disorganization (at 30 umol/photon/m(2)/s, sterile air) (PubMed:22368073). The latter mutant is able to concentrate inorganic carbon but cannot use it to fix CO(2) (PubMed:22368073). The truncated protein is constitutively expressed at 30 and 20 degrees Celsius and is no longer subject to normal regulation i.e. has lost cold-shock induction and dark-induced repression (PubMed:23119089, PubMed:24509313). Belongs to the DEAD box helicase family.