Gene Expression and Silencing Studies in Phytophthora infestans Reveal Infection-Specific Nutrient Transporters and a Role for the Nitrate Reductase Pathway in Plant Pathogenesis.
Gene Expression and Silencing Studies in Phytophthora infestans Reveal Infection-Specific Nutrient Transporters and a Role for the Nitrate Reductase Pathway in Plant Pathogenesis.
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DOI：
10.1371/journal.ppat.1006097
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发表时间：
2016-12
期刊：
影响因子：
6.7
通讯作者：
Judelson HS
中科院分区：
文献类型：
--
作者：
Abrahamian M;Ah-Fong AM;Davis C;Andreeva K;Judelson HS
为了帮助了解植物病原体如何从宿主身上获取营养，对来自半生物营养型马铃薯和番茄害虫致病疫霉的营养转运蛋白基因进行了注释。这鉴定出了来自 19 个家族的 453 个基因。与坏死营养型卵菌，终极腐霉变种的比较。 ultimum 和半生物营养真菌 Magnaporthe oryzae 揭示了一些家族大小的多样性，尽管编码转运蛋白的基因比例相似。对受感染的马铃薯块茎、番茄叶子和几种人工培养基进行的 RNA 测序显示，在叶子或块茎相对于培养基的早期感染时间点，来自致病疫霉的 56 个和 207 个转运蛋白分别显着上调或下调。与培养基相比，大约 17 个在叶子和块茎中上调超过 4 倍，并且主要在生物营养阶段表达。许多基因的转录模式是宿主器官特异性的。例如，在感染中期，富含硝酸盐的叶子中硝酸盐转运蛋白（NRT）的 mRNA 水平比块茎和三种缺乏硝酸盐的人工培养基中的 mRNA 水平高出约 100 倍。 NRT 基因与编码硝酸盐还原酶 (NR) 和亚硝酸盐还原酶 (NiR) 的基因物理连接，后者将硝酸盐转化为铵和氨基酸。所有三个基因都是共同调控的。例如，这三个基因主要在马铃薯和番茄叶片的中期感染时间点表达，但在马铃薯块茎中几乎没有表达。所有三个基因均下调的转化子是通过 DNA 指导的 RNAi 产生的，沉默从 NR 靶标扩散到侧翼的 NRT 和 NiR 基因。沉默的菌株在叶子上不致病，但在块茎上定殖。我们认为硝酸盐同化基因在获得氨基酸生物合成所需的氮和保护致病疫霉免受自然或施肥诱导的硝酸盐和亚硝酸盐毒性方面发挥作用。人们对植物病原体如何适应不同的生长条件和宿主组织知之甚少。为了了解丝状真核微生物致病疫霉与其马铃薯和番茄宿主之间的相互作用，我们挖掘了基因组中编码参与营养吸收的蛋白质的基因，并测量了它们在叶子、块茎和三种人工培养基中的表达。我们观察了生长条件之间的动态变化，并确定了主要在生物营养阶段、叶子、块茎或人工培养基中表达的转运蛋白。当我们阻断硝酸盐转运蛋白和另外两个参与硝酸盐同化的基因的表达时，我们观察到这些基因是成功定植富含硝酸盐的叶子所必需的，而不是缺乏硝酸盐的组织，并且硝酸盐对沉默的菌株产生了毒性。因此，我们假设硝酸盐同化途径可能有助于病原体利用无机氮作为营养和/或在硝酸盐水平可能变得有害时对其进行解毒。
To help learn how phytopathogens feed from their hosts, genes for nutrient transporters from the hemibiotrophic potato and tomato pest Phytophthora infestans were annotated. This identified 453 genes from 19 families. Comparisons with a necrotrophic oomycete, Pythium ultimum var. ultimum, and a hemibiotrophic fungus, Magnaporthe oryzae, revealed diversity in the size of some families although a similar fraction of genes encoded transporters. RNA-seq of infected potato tubers, tomato leaves, and several artificial media revealed that 56 and 207 transporters from P. infestans were significantly up- or down-regulated, respectively, during early infection timepoints of leaves or tubers versus media. About 17 were up-regulated >4-fold in both leaves and tubers compared to media and expressed primarily in the biotrophic stage. The transcription pattern of many genes was host-organ specific. For example, the mRNA level of a nitrate transporter (NRT) was about 100-fold higher during mid-infection in leaves, which are nitrate-rich, than in tubers and three types of artificial media, which are nitrate-poor. The NRT gene is physically linked with genes encoding nitrate reductase (NR) and nitrite reductase (NiR), which mobilize nitrate into ammonium and amino acids. All three genes were coregulated. For example, the three genes were expressed primarily at mid-stage infection timepoints in both potato and tomato leaves, but showed little expression in potato tubers. Transformants down-regulated for all three genes were generated by DNA-directed RNAi, with silencing spreading from the NR target to the flanking NRT and NiR genes. The silenced strains were nonpathogenic on leaves but colonized tubers. We propose that the nitrate assimilation genes play roles both in obtaining nitrogen for amino acid biosynthesis and protecting P. infestans from natural or fertilization-induced nitrate and nitrite toxicity. Little is known of how plant pathogens adapt to different growth conditions and host tissues. To understand the interaction between the filamentous eukaryotic microbe Phytophthora infestans and its potato and tomato hosts, we mined the genome for genes encoding proteins involved in nutrient uptake and measured their expression in leaves, tubers, and three artificial media. We observed dynamic changes between the growth conditions, and identified transporters expressed mainly in the biotrophic stage, leaves, tubers, or artificial media. When we blocked the expression of a nitrate transporter and two other genes involved in assimilating nitrate, we observed that those genes were required for successful colonization of nitrate-rich leaves but not nitrate-poor tissues, and that nitrate had become toxic to the silenced strains. We therefore hypothesize that the nitrate assimilation pathway may help the pathogen use inorganic nitrogen for nutrition and/or detoxify nitrate when its levels may become damaging.
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影响因子：
4.4
作者：
Attard, Agnes;Evangelisti, Edouard;Gourgues, Mathieu
通讯作者：
Gourgues, Mathieu
影响因子：
2.5
作者：
Cui, Zhifeng;Gao, Nana;Zhu, Tingheng
通讯作者：
Zhu, Tingheng
影响因子：
7.2
作者：
Elgin, Sarah C. R.;Reuter, Gunter
通讯作者：
Reuter, Gunter
影响因子：
9.4
作者：
BURTON, W. G.;SPRAGG, W. T.
通讯作者：
SPRAGG, W. T.
DOI：
10.1073/pnas.89.5.1861
发表时间：
1992-03-01
影响因子：
11.1
作者：
CHENG, CL;ACEDO, GN;CONKLING, MA
通讯作者：
CONKLING, MA