Molecular karyotypes for Alternaria plant pathogens known to produce host-specific toxins

Abstract

There are at least ten plant diseases caused by Alternaria species in which host-specific toxins (HSTs) are responsible for fungal pathogenicity. Of these HST-producers, seven are considered distinct pathotypes of the species Alternaria alternata, and the remaining three are among other species of pathogenic Alternaria. Inter- and intra-specific variation among Alternaria taxa, including HST-producers, was determined by electrophoretic karyotyping using pulsed-field gel electrophoresis. A. alternata including seven pathotypes of A. alternata and eight non-pathogenic strains had 9-11 chromosomal bands with estimated sizes ranging from 0.4 to 5.7 Mb. In contrast, Alternaria species that are morphologically distinct from A. alternata had 8-10 bands with sizes between 0.9 and 5.7 Mb. Estimated genome sizes of A. alternata and other Alternaria species ranged from 28.8 to 33.6 Mb and 25.1 to 30.7 Mb, respectively. Other species of pathogenic Alternaria were difficult to differentiate from A. alternata on the basis of chromosome-size polymorphisms alone, but Southern analysis using rDNA as a probe could, in some cases, differentiate between them. These results were cytologically confirmed by 4',6-diamidino-2-phenylindole (DAPI) staining and fluorescence in situ hybridization with a rDNA probe for mitotic metaphase chromosomes prepared by the germ-tube burst method.

Horizontal Chromosome Transfer, a Mechanism for the Evolution and Differentiation of a Plant-Pathogenic Fungus

“…The weak signal obtained for ECs in almost all isolates was probably due to hybridization of the probe to rDNA, given that rDNA is a highly multicopy gene and it is difficult to remove the trace amounts of contaminating rDNA from the probe DNA. The chromosomes demonstrating weak signal corresponded to those harboring rDNA sequences (5). The nature of the 1.0-Mb chromosome is in agreement with the criteria determined for supernumerary chromosomes (10).…”

“…There is also clear evidence of recent lateral gene transfer of the ToxA gene from Stagonospora nodorum to P. tritici-repentis (14,30). In Alternaria alternata plant pathogens (37), we have shown that all strains of the A. alternata pathotypes harbor small extra chromosomes of less than 1.7 Mb, whereas nonpathogenic isolates do not have these small chromosomes (5). A cyclic peptide synthetase gene, AMT, which is involved in host-specific AM toxin biosynthesis of the apple pathotype of A. alternata, was located on a small chromosome of 1.1 to 1.7 Mb, depending on the strain (22,23).…”

“…Chromosomal DNA was prepared as described by Akamatsu et al (5). Contour-clamped homogeneous electric field (CHEF) pulsed-field gel electrophoresis (PFGE) was used to separate intact chromosomes with a CHEF DR-III apparatus (Bio-Rad).…”

Biosynthesis of secondary metabolites in plant pathogenic fungi and their involvement in pathogenicity; a genomics-based approach for understanding their evolution and diversity.

“…異的 AAL 毒素を生産し，愛知ファーストなどの特定のトマ ト品種に病気を引き起こす (Akamatsu et al, 1997;Gilchrist & Grogan, 1976;Peever et al, 2004) ．本毒素は，Fusarium 属 病原菌が生産するマイコトキシンのフモニシンに化学構造 および生物活性が類似している (Bottini et al, 1981;Caldas et al, 1995;Musser and Plattner, 1997) (Bojja et al, 2004;Butchko et al, 2006;Proctor et al, 2003Proctor et al, , 2006 (Akagi et al, 2009a, b;Akamatsu et al, 1999;Covert, 1998;Johnson et al, 2001 …”

Karyotyping Methods for Fungi

“…This method was further modifi ed and developed for various other fungal species during the past decade (3)(4)(5)(6)(7)(8)(9) . Basically, conidia are suspended in complete medium and placed on a glass slide for germination.…”