Genome Organization inBeauveria bassiana:Electrophoretic Karyotype, Gene Mapping, and Telomeric Fingerprint

Abstract

Viaud, M., Couteaudier, Y., Levis, C., and Riba, G. 1996. Genome organization inBeauveria bassiana:Electrophoretic karyotype, gene mapping, and telomeric fingerprint.Fungal Genetics and Biology20,175–183. Using telomeric fingerprint and pulsed-field gel electrophoresis, we have analyzed the chromosomal organization among nine entomogenousBeauveria bassianaisolates. A heterologous telomeric probe established that the minimum number of chromosomes was between seven and eight among isolates. Chromosomal DNA was electrophoresed by using contour-clamped homogenous electric field (CHEF) gel electrophoresis. Five to eight chromosomal bands were separated among isolates. Substantial variation in band intensity suggested the presence of some chromosome doublets. The deduced karyotypes were in agreement with the minimum chromosome number reported from telomeric fingerprints. The minimum total genome size was estimated to range from 34.3 to 44.1 Mb. Significant chromosome length polymorphism was observed in karyotypes in the speciesB. bassianaexcept within isolates from one insect,Ostrinia nubilalis.Specific hybridization to chromosomes on CHEF gels was obtained by using homologous genes for proteinase 1, 28S rDNA, β-tubulin, histone 4, nitrate reductase, and the mitochondrial small rDNA. The mitochondrial DNA had a slow mobility in comparison to its circular size, probably because of the presence of very long linear molecules. Comparison of karyotype profiles following Southern analysis demonstrated a very flexible chromosomal organization among isolates from different origins and has confirmed the similarities withinO. nubilalisisolates.