Molecular cytogenetic analysis of the chromosome evolution in the mycotoxin-producing Fusarium species

点击翻译按钮获取中文摘要

In this research project, molecular cytogenetic study was carried out on the karyotypes and chromosomes of mycotoxin-producing Fusarium spp. such as F.graminearum, and the data were analyzed in relation to the evolution of this group. The main results obtained are as follows.1. The detailed karyotypes including chromosome number (n=4) and morphological feature of chromosomes were determined for the standard strains PH-1 and 00-676 that were used for genome sequencing project. Each chromosome was corresponded to the specific genetic linkage group.2. Both cytological and electrophoretic karyotypes were determined for 21 species (35 strains) collected from 12 countries. The data showed that each species has constant, species-specific chromosome number and also that species can be classified into three groups based on the chromosome number, that is, groups with n=4 (9 spp. including F graminearum), n=5 (17 equiseti and F.longipes), n=8 (4 spp. including F. avenaceum), and n=12 (6 spp. including F.fujikuro), respectively.3. Molecular phylogenic trees were constructed using DNA sequences of TEF-1 and histone H3, and relationships between phylogeny and chromosome number of the species was analyzed. The results indicated that the mycotoxin-producing Fusarium spp. evolved in the two independent routes, namely, n【greater than or equal】12→n=8 and n【greater than or equal】12→n=4. Probably, chromosomes constituting n=4 was formed by fusion of small chromosomes of the ancestor (chromosome fusion hypothesis).4. In order to prove chromosome fusion hypothesis, chromosome painting FISH was performed to the metaphase chromosomes of F. graminearum using chromosomal DNAs of F. proliferatum as probes. In this analysis, 0.7-Mb chromosome of F. proliferatum was allocated to the distal region of chromosome 4 of F. graminearum.