Role of Silencing RNA fgsiR34 in Fusarium Graminearum's Pathogenicity to Wheat

<p><em>Fusarium graminearum</em> is an ascomycetous fungal pathogen that causes Fusarium head blight (FHB) disease in wheat and other cereal grains. Mycotoxin produced by the fungus, predominantly deoxynivalenol (DON), is considered as an important virulence factor for the spread of disease. Our previous study of a <em>Dicer-like 2</em> knockdown mutant has led to our hypothesis that a silencing RNA, <em>fgsiR34</em>, might play a key role in regulating DON biosynthesis and some other virulent factors. To test this hypothesis, we generated an<em> fgsiR34</em> over-expressing mutant (<em>ΔfgsiR34+</em>) using Inverse Repeat Transgene method and studied the pathogenicity of the mutant in wheat. Though no phenotypic alterations, such as spore production and growth rate on solid media, were found in the mutant in comparison with the wildtype strain, altered expressions of <em>Tri</em> genes and other pathogenic genes were observed. <em>Tri4, Tri5, Tri6, Tri10</em>, and <em>Tri14</em> were all significantly downregulated, while the cell wall degrading enzymes (CWDEs) were upregulated in <em>ΔfgsiR34+</em> strain. Wheat spikelets inoculated with <em>ΔfgsiR34+</em> showed a significant downregulation of both Tri5 and Tri6. The disease progression and F. graminearum biomass were significantly reduced in <em>ΔfgsiR34+</em>-inoculated FHBsusceptible NIL compared to the wildtype-inoculated ones. To understand the mechanism of the pathogenic role by <em>fgsiR34</em>, we analyzed the methylation pattern of the seed region of <em>fgsiR34</em> at nearly 1000 bp upstream of <em>Tri5</em> to elucidate if <em>fgsiR34</em> induces methylation to suppress expression of <em>Tri</em> genes. After bisulfite treatment and methylation-specific PCR we found that the seed region of <em>fgsiR34</em> in both the wildtype and the<em> ΔfgsiR34+</em> strains was not methylated. In summary, our results suggested that <em>fgsiR34</em> negatively regulates <em>Tri</em> genes biosynthesis pathway, while positively regulates CWDEs. All these results imply a significant, complex role of <em>fgsiR34</em> in regulating <em>Tri</em> genes biosynthesis. It seems that methylation is not involved in repressing the expression of <em>Tri</em> genes. Interestingly, our RT-qPCR assay of non-coding transcript within the seed region revealed that the <em>fgsiR34</em> seed region was transcribed with increased transcript abundance in the<em> ΔfgsiR34+</em> mutant over the wildtype, suggesting a role of the non-coding transcript in regulating expression of <em>Tri</em> genes. More research is, therefore, needed to elucidate the mechanisms of FHB pathogenicity by <em>fgsiR34</em>.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis - Open Access

Discipline thesis:degree_discipline

Biology and Microbiology

Year dc:date.available

2016

Author dc:creator

• Dahal, Subha

Contributors dc:contributor

• Yang Yen

• fgsiR34
• Fusarium graminearum
• Fusarium head blight
• pathogenicity
• small RNAs
• trichothecenes
• Biology
• Microbiology
• Plant Biology

Licence

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language

en

Repository record dc:identifier

https://openprairie.sdstate.edu/etd/1103

OAI identifier oai:identifier

oai:openprairie.sdstate.edu:etd-2105