Department of Plant Science, Weizmann Institute of Science, 76100 Rehovot, Israel.
Mol Plant Pathol. 2005 Jul 1;6(4):459-70. doi: 10.1111/j.1364-3703.2005.00297.x.
SUMMARY Nitrogen is an essential growth component whose availability will limit microbial spread, and as such it serves as a key control point in dictating an organism's adaptation to various environments. Little is known about fungal nutrition in planta. To enhance our understanding of this process we examined the transcriptional adaptation of Fusarium oxysporum f. sp. lycopersici, the causal agent for vascular wilt in tomato, during nutritional stress and plant colonization. Using RT-PCR and microarray technology we compared fungal gene expression in planta to axenic nitrogen starvation culture. Several expressed sequence tags, representing at least four genes, were identified that are concomitantly induced during nitrogen starvation and in planta growth. Three of these genes show similarity to a general amino acid permease, a peptide transporter and an uricase, all functioning in organic nitrogen acquisition. We further show that these genes represent a distinguishable subset of the nitrogen-responsive transcripts that respond to amino acids commonly available in the plant. Our results indicate that nitrogen starvation partially mimics in planta growth conditions, and further suggest that minute levels of organic nitrogen sources dictate the final outcome of fungal gene expression in planta. The nature of the identified transcripts suggests modes of nutrient uptake and survival for Fusarium during colonization.
摘要 氮是一种必需的生长成分，其可用性将限制微生物的扩散，因此它是决定生物体适应各种环境的关键控制点。关于植物体内真菌的营养知之甚少。为了增强我们对这一过程的理解，我们研究了番茄维管束萎蔫病原菌尖孢镰刀菌（Fusarium oxysporum f. sp. lycopersici）在营养胁迫和植物定殖过程中的转录适应性。我们使用 RT-PCR 和微阵列技术比较了在植物体内和在无氮饥饿培养物中真菌的基因表达。鉴定出了至少四个基因的表达序列标签，这些基因在氮饥饿和植物生长过程中同时被诱导。其中三个基因与一种通用氨基酸渗透酶、一种肽转运体和一种尿酸酶具有相似性，所有这些酶都参与有机氮的获取。我们进一步表明，这些基因代表了对植物中常见氨基酸有反应的氮响应转录本的一个可区分的子集。我们的结果表明，氮饥饿部分模拟了植物生长条件，并进一步表明，痕量的有机氮源决定了真菌在植物体内基因表达的最终结果。所鉴定的转录本的性质表明了尖孢镰刀菌在定殖过程中吸收和存活的营养方式。
