Phytophthora infestans Sporangia Produced in Culture and on Tomato Leaflet Lesions Show Marked Differences in Indirect Germination Rates, Aggressiveness, and Global Transcription Profiles
Phytophthora infestans Sporangia Produced in Culture and on Tomato Leaflet Lesions Show Marked Differences in Indirect Germination Rates, Aggressiveness, and Global Transcription Profiles
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DOI：
10.1094/mpmi-09-18-0255-ta
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发表时间：
2019-05-01
影响因子：
3.5
通讯作者：
Fei, Zhangjun
中科院分区：
文献类型：
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作者：
Fry, William E.;Patev, Sean P.;Fei, Zhangjun
来自琼脂平板上纯培养物的致病疫霉孢子囊通常用于实验室研究，而来自小叶病变的孢子囊驱动自然感染和流行病。进行了多次试验，以确定这两种来源的孢子囊是否等同。从平板培养的孢子囊显示出低得多的间接发芽率，并在田间和室内试验中产生少得多的疾病。无论孢子囊是否预先在4 ℃（以诱导间接萌发）或21 ℃（以防止间接萌发）下孵育，都观察到这种侵袭性的差异。此外，由平板孢子囊引起的病变产生的孢子形成要少得多。RNA-Seq分析揭示，与来自小叶病变的那些分离株的孢子囊相比，具有RPKM（每百万个映射读数中每个外显子模型的内切酶的读数）>1的> 17，000个致病疫霉基因中的数千个在从两个独立田间分离株的平板培养物获得的孢子囊中差异表达。在显著的差异表达基因（DEG）中，推定的RxLR效应子过度表达，在RPKM >1的355个效应子中几乎有一半上调或下调。这两个分离物的DEG包括9个鞭毛相关基因，所有下调板孢子囊。10 elicitin基因也被检测到DEG在两个分离物，和9（包括INF 1）在板孢子囊上调。这些结果证实了以前的观察，孢子囊产生的板和小叶有时会产生不同的实验结果，并提出假设的潜在机制。我们警告说，在测定中使用平板孢子囊可能并不总是产生反映自然感染和流行病的结果。
Sporangia of Phytophthora infestans from pure cultures on agar plates are typically used in lab studies, whereas sporangia from leaflet lesions drive natural infections and epidemics. Multiple assays were performed to determine if sporangia from these two sources are equivalent. Sporangia from plate cultures showed much lower rates of indirect germination and produced much less disease in field and moist-chamber tests. This difference in aggressiveness was observed whether the sporangia had been previously incubated at 4 degrees C (to induce indirect germination) or at 21 degrees C (to prevent indirect germination). Furthermore, lesions caused by sporangia from plates produced much less sporulation. RNA-Seq analysis revealed that thousands of the >17,000 P. infestans genes with a RPKM (reads per kilobase of exon model per million mapped reads) >1 were differentially expressed in sporangia obtained from plate cultures of two independent field isolates compared with sporangia of those isolates from leaflet lesions. Among the significant differentially expressed genes (DEGs), putative RxLR effectors were overrepresented, with almost half of the 355 effectors with RPKM >1 being up- or downregulated. DEGs of both isolates include nine flagellar-associated genes, and all were down-regulated in plate sporangia. Ten elicitin genes were also detected as DEGs in both isolates, and nine (including INF1) were up-regulated in plate sporangia. These results corroborate previous observations that sporangia produced from plates and leaflets sometimes yield different experimental results and suggest hypotheses for potential mechanisms. We caution that use of plate sporangia in assays may not always produce results reflective of natural infections and epidemics.