Katoh H, Asthana R K, Ohmori M
Department of Life Sciences (Biology), University of Tokyo, Komaba 3-8-1, Meguro, Tokyo 153-8902, Japan.
Microb Ecol. 2004 Feb;47(2):164-74. doi: 10.1007/s00248-003-1043-6. Epub 2004 Feb 2.
The N2-fixing cyanobacterium Anabaena sp. PCC7120 showed an inherent capacity for desiccation tolerance. A DNA microarray covering almost the entire genome of Anabaena was used to determine the genome-wide gene expression under desiccation. RNA was extracted from cells at intervals starting from early to late desiccation. The pattern of gene expression in DNA fragments was categorized into seven types, which include four types of up-regulated and three types of down-regulated fragments. Validation of the data was carried out by RT-PCR on selected up-regulated DNA fragments and was consistent with the changes in mRNA levels. Our conclusions regarding desiccation tolerance for Anabaena sp. PCC7120 are as follows: (i) Genes for osmoprotectant metabolisms and the K+ transporting system are up-regulated from early to mid-desiccation; (ii) genes induced by osmotic, salt, and low-temperature stress are up-regulated under desiccation; (iii) genes for heat shock proteins are up-regulated after mid-desiccation; (iv) genes for photosynthesis and the nitrogen-transporting system are down-regulated during early desiccation; and (v) genes for RNA polymerase and ribosomal protein are down-regulated between the early and the middle phase of desiccation. Profiles of gene expression are discussed in relation to desiccation acclimation.
固氮蓝藻鱼腥藻Anabaena sp. PCC7120表现出固有的耐干燥能力。利用覆盖鱼腥藻几乎整个基因组的DNA微阵列来确定干燥条件下全基因组的基因表达情况。从干燥初期到后期，每隔一段时间从细胞中提取RNA。DNA片段中的基因表达模式分为七种类型，包括四种上调类型和三种下调类型。通过对选定的上调DNA片段进行RT-PCR对数据进行验证，结果与mRNA水平的变化一致。我们关于鱼腥藻Anabaena sp. PCC7120耐干燥能力的结论如下：（i）渗透保护剂代谢和钾离子转运系统的基因在干燥初期到中期上调；（ii）由渗透、盐和低温胁迫诱导的基因在干燥条件下上调；（iii）热休克蛋白的基因在干燥中期后上调；（iv）光合作用和氮转运系统的基因在干燥初期下调；（v）RNA聚合酶和核糖体蛋白的基因在干燥早期和中期之间下调。文中结合干燥适应性对基因表达谱进行了讨论。
