A DNA microarray, comprising 70-mer oligonucleotides, representing 8,453 open reading frames (ORFs), was constructed based on the Bradyrhizobium japonicum strain USDA110 genomic sequence. New annotation predicted 199 additional genes, which were added to the microarray and were shown to be transcribed. These arrays were used to profile transcription in cells under a variety of conditions, including growth in minimal versus rich medium, osmotic stress, and free-living cells versus bacteroids. Increased expression was seen for genes involved in translation, motility, and cell envelope synthesis in rich medium whereas expression increased in minimal medium for genes involved in vitamin biosynthesis and stress responses. Treatment with 50 mM NaCl activated stress-inducible genes but repressed genes involved in chemotaxis and motility. Strikingly, no known transport systems for accumulation of compatible solutes or osmoprotectants were induced in response to osmotic stress. A number of nif, fix, and hup genes, but not all, were upregulated in bacteroids. The B. japonicum type III secretion system, known to be important in early nodulation, was downregulated in bacteroids. The availability of a reliable, low-cost B. japonicum microarray provides a useful tool for functional genomic studies of one of the most agriculturally important bacteria.

译文

:基于日本根瘤菌(Bradyrhizobium japonicum)菌株USDA110基因组序列,构建了一个DNA芯片,该芯片包含70个寡核苷酸,代表8453个开放阅读框(ORF)。新的注释预测了199个其他基因,这些基因已添加到微阵列中并显示为可转录的。这些阵列用于在各种条件下分析细胞中的转录情况,包括在最少量培养基与丰富培养基中的生长,渗透压以及在自由生活中的细胞与类细菌的生长。在丰富的培养基中,涉及翻译,运动和细胞包膜合成的基因表达增加,而在涉及维生素生物合成和应激反应的基因的基本培养基中,表达增加。用50 mM NaCl处理可激活应激诱导基因,但抑制了涉及趋化性和运动性的基因。令人惊讶的是,没有任何已知的响应于渗透压的积累相容性溶质或渗透保护剂的转运系统被诱导出来。许多nif,fix和hup基因(但不是全部)在类细菌中上调。已知在早期结瘤中很重要的日本血吸虫III型分泌系统在类细菌中被下调。可靠,低成本的日本根瘤菌微阵列的可用性为最重要的农业细菌之一的功能基因组研究提供了有用的工具。

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