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United States Department of Agriculture

Agricultural Research Service

Title: Nuclear Small Subunit Rrna Group I Intron Variation among Beauveria Spp Provide Tools for Strain Identification and Evidence of Horizontal Transfer

Authors
item Coates, Brad
item Hellmich, Richard
item Lewis, Leslie

Submitted to: Current Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 20, 2002
Publication Date: August 1, 2002
Citation: COATES, B.S., HELLMICH II, R.L., LEWIS, L.C. NUCLEAR SMALL SUBUNIT RRNA GROUP I INTRON VARIATION AMONG BEAUVERIA SPP PROVIDE TOOLS FOR STRAIN IDENTIFICATION AND EVIDENCE OF HORIZONTAL TRANSFER. CURRENT GENETICS. 2002. V. 41. P. 414-424.

Interpretive Summary: Beauveria bassiana is a filamentous fungus that is pathogenic towards several crop pest insects including the European corn borer (ECB). Different strains of Beauveria bassiana vary greatly in ability to kill ECB larvae, and cannot be identified visually. We investigated a region of this pathogen's DNA known to have a large intron inserted. We showed that introns were slightly different among strains, and developed methods to quickly identify genetic differences between strains. The protocols developed will allow scientists to uniquely identify strains of Beauveria bassiana, determine relatedness among isolates highly virulent against ECB, and track them in field and laboratory experiments. This information will be useful for all stakeholders interested in finding biological ways to control European corn borers.

Technical Abstract: An optional group I intron was characterized at a single insertion point in nuclear small subunit rRNA (nuSSU rRNA) genes of the entomopathogenic fungi, Beauveria bassiana and B. brongniartii. Insertion points were conserved among nuSSU rRNA genes from 40 Beauveria isolates. PCR-RFLP and DNA sequencing identified twelve group I intron variants, and an alignment of 383 to 404 nucleotide-long group I introns indicated that four indel mutations were the main basis of fragment length variation. Features of primary sequence resulted in classification of all introns into subgroup IB3. Phylogeny reconstruction using parsimony and neighbor-joining methods suggested six lineages may be present among SSU rRNA group I intron sequences from Beauveria and related ascomycete fungi. Group I introns from three Beauveria isolates formed a lineage distinct from that of 12 others. Sequence variability and low intron penetrance suggested ancient acquisition of a highly mobile element that may have undergone horizontal transfer.

Last Modified: 9/2/2014
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