Biological roles of small RNAs expressed during infection of barley by the obligate fungal biotroph, Blumeria graminis f. sp. hordei

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2018-01-01
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Hunt, Matthew
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Roger Wise
Steven Whitham
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Plant Pathology and Microbiology
The Department of Plant Pathology and Microbiology and the Department of Entomology officially merged as of September 1, 2022. The new department is known as the Department of Plant Pathology, Entomology, and Microbiology (PPEM). The overall mission of the Department is to benefit society through research, teaching, and extension activities that improve pest management and prevent disease. Collectively, the Department consists of about 100 faculty, staff, and students who are engaged in research, teaching, and extension activities that are central to the mission of the College of Agriculture and Life Sciences. The Department possesses state-of-the-art research and teaching facilities in the Advanced Research and Teaching Building and in Science II. In addition, research and extension activities are performed off-campus at the Field Extension Education Laboratory, the Horticulture Station, the Agriculture Engineering/Agronomy Farm, and several Research and Demonstration Farms located around the state. Furthermore, the Department houses the Plant and Insect Diagnostic Clinic, the Iowa Soybean Research Center, the Insect Zoo, and BugGuide. Several USDA-ARS scientists are also affiliated with the Department.
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Plants and their pathogens have constantly co-evolving mechanisms that determine infection success. Small RNAs (sRNAs) of 18-30 nucleotides can have a large effect regulating plant defense responses as well as fungal virulence factors. The goal of this project was to understand how sRNAs regulate gene expression both for species of origin, as well as trans-kingdom sRNA communication between barley and Blumeria graminis f. sp. hordei (Bgh), the causal agent of barley powdery mildew. To accomplish this goal we examined Bgh sRNA expression over a time course representing the key stages of Bgh infection of barley (appressorium formation, penetration of epidermal cells, and development of haustoria) in five barley lines including four fast-neutron derived immune-signaling mutants and their progenitor line CI 16151. The sRNA expression data was complemented by parallel analysis of RNA ends (PARE) analysis that confirms sRNA transcript cut sites with in vivo data. In barley, conserved and novel miRNAs were identified with predicted target transcripts enriched in the transcriptional regulation, signaling, and photosynthesis categories. Phasing siRNAs (phasiRNAs) were also identified in barley overlapping with protein coding genes including receptor-like kinases and resistance genes. Bgh micro RNA-like RNAs (milRNAs) were identified that are predicted to regulate transcripts encoding effectors, metabolic proteins, and translation-related proteins. A subset of effectors homologous to the AVRk1 and AVRa10 (EKA) family may be regulated by a sRNA-encoding hairpin that is overlapping and antiparallel to an EKA gene. These genes are heavily regulated by sRNAs, in contrast to most Bgh protein-coding genes. Potential trans-kingdom functional sRNAs were identified from both barley and Bgh. The predicted Bgh trans-kingdom sRNA are highly enriched in transcripts that function in non-species-specific defenses. The transcript targets encode proteins related to vesicle secretion, cell wall synthesis, protein turnover, transcriptional regulation, ROS response, and fungal cell wall breakdown. The potential barley trans-kingdom sRNAs are predicted to target Bgh transcripts including Bgh-specific effector proteins, ribosome synthesis/function, core transcription factors, and cell cycle regulators. Overall, these findings indicate that sRNAs are integral in regulation of gene expression during Bgh infection of barley leaves.

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Wed Aug 01 00:00:00 UTC 2018