Abstract
The establishment of host-microbe interactions requires molecular communication between both partners, which involves the mutual transfer of noncoding small RNAs. Previous evidence suggests that this is also true for the barley powdery mildew disease, which is caused by the fungal pathogen Blumeria hordei. However, previous studies lacked spatial resolution regarding the accumulation of small RNAs upon host infection by B. hordei. Here, we analysed site-specific small RNA repertoires in the context of the barley-B. hordei interaction. To this end, we dissected infected leaves into separate fractions representing different sites that are key to the pathogenic process: epiphytic fungal mycelium, infected plant epidermis, isolated haustoria, a vesicle-enriched fraction from infected epidermis, and extracellular vesicles. Unexpectedly, we discovered enrichment of specific 31- to 33-base long 5’-terminal fragments of barley 5.8S ribosomal RNA (rRNA) in extracellular vesicles and infected epidermis, as well as particular B. hordei tRNA fragments in haustoria. We describe canonical small RNAs from both the plant host and the fungal pathogen that may confer cross-kingdom RNA interference activity. Interestingly, we found first evidence of phased small RNAs (phasiRNAs) in B. hordei, a feature usually attributed to plants, which may be associated with the post-transcriptional control of fungal coding genes, pseudogenes, and transposable elements. Our data suggests a key and possibly site-specific role for cross-kingdom RNA interference and noncoding RNA fragments in the host-pathogen communication between B. hordei and its host barley.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Error in the title (typographical insertion lead to spurious title)
Abbreviations
- Ago
- Argonaute
- Dcl
- Dicer-like
- EPI
- epidermis (colonized by B. hordei but epiphytic fungal mycelium removed)
- dsRNA
- double-stranded RNA
- EV
- extracellular vesicle
- FDR
- false discovery rate
- GO
- gene ontology
- HAU
- haustoria of B. hordei
- milRNA
- micro RNA-like
- miRNA
- micro RNA
- MYC
- mycelium of B. hordei
- phasiRNA
- phased siRNA
- P40
- microsomes from B. hordei-infected epidermis
- RNAi
- RNA interference
- rDNA
- ribosomal DNA
- rRF
- ribosomal RNA-derived small RNA fragment
- rRNA
- ribosomal RNA
- sRNA
- small RNA
- siRNA
- small interfering RNA
- tasiRNA
- trans-acting short interfering RNA
- TPM
- transcripts per million
- tRF
- transfer RNA-derived small RNA fragment
- tRNA
- transfer RNA