Cold acclimation of cyanobacteria involves the regulation of many genes, such as crhR that encodes RNA helicase.In this study, the transcription ofcrhR was examined in Synechocystis sp. PCC 6803 transferred from 30℃ to 15℃, and its transient expression was found within 2h. Inactivation of this gene in the cyanobacterium led to loss of growth at 15℃, great reduction of photosynthetic and respiratory activities, and inability to eliminate lipid peroxides. Overexpression of crhR from PrbcL in the crhR mutant fully complemented the mutation, and the complemented strain showed slightly improved growth at 15℃ compared to the wild type. In the wild type, temperature downshift induced the up-regulation of fatty acid desaturase genes desA, desB and desD and the increase of unsaturation degree of fatty acids. In the crhR mutant, the induction of desB by temperature downshift was significantly reduced, and the contents of polyunsaturated fatty acids were not increased under the same conditions. It is proposed that crhR may directly affect protein synthesis in the cyanobacterium under low-temperature stress, or indirectly, exert its effects on enzyme activities by regulating the expression of chaperone genes.%蓝藻对低温胁迫的适应涉及许多基因的表达调控,RNA解旋酶基因crhR即是其中之一.研究检查了该基因在集胞藻PCC6803从30℃转到15℃后的转录情况,观察剑在2h内有瞬时诱导表达.该基因失活导致集胞藻在15℃下几乎不能生长,光合作用和呼吸速率大幅下降,脂质过氧化物不能被有效清除.以PrbcL过量表达crhR基因可互补突变株表型,并且在低温下生长略优于野生型.在野生型中,低温诱导脂肪酸脱饱和酶基因desA、desB、desD表达上调,膜脂不饱和度增加;而在crhR突变株中,低温诱导的desB基因的上调表达显著削弱,同时多不饱和脂肪酸含量没有显著增加.推测crhR基因可能影响蓝藻在低温胁迫下的蛋白合成或通过伴侣蛋白发挥影响.
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