digitatum have been limited. Mitochondria are generally accepted as having a common origin and play an important role in phylogenetic studies. Many programmes,

such as the Fungal Mitochondrial Genome Project (Paquin et al., 1997), have significantly increased the data on fungal mitochondria and more than 80 complete fungal mitochondrial genomes are available in NCBI (www.ncbi.nlm.nih.gov/genomes/GenomesGroup.cgi?taxid=4751&opt=organelle). Information acquired from mitochondria, e.g. gene content and arrangement, exon–intron structure, as well as molecular phylogeny based on single or concatenated mitochondrial protein sequences, has largely increased our knowledge of Penicillium and its closely related Aspergillus species (Woo et al., Caspase inhibitor 2003; Juhasz et al., 2004, 2008). However, phytopathogenic Penicillium species have not been well described.

To reveal the mechanisms of molecular plant–pathogen interactions, whole genome sequencing of P. digitatum has been initiated in our laboratory. Here we reveal the mitochondrial genome and use comparative analysis to further confirm the species’ evolutionary degree, and to explore polymophism in Penicillium mitochondrial genomes. Penicillium digitatum strain Pd01 was isolated from green mould diseased citrus fruit collected in Zhejiang province, China, in 2000. It was maintained on potato selleck screening library dextrose agar medium at 4 °C. The mycelium of Pd01 was cultured in potato dextrose broth in a rotary shaker at 150 g at 25 °C for 4 days. Fresh harvested Pd01 mycelia (100 mg) were homogenized in a mortar precooled with liquid nitrogen.

The subsequent powder was transferred to a 2-mL Eppendorf tube, then incubated at 65 °C for 1 h after adding 0.8 mL however CTAB buffer (1% CTAB, 1 M NaCl 100 mM Tris, 20 mM EDTA; 1% polyvinyl polypyrolidone and 1% β-mercaptoethanol). Thereafter, 0.8 mL chloroform/isoamyl alcohol (24 : 1, v/v) was added to the tube. After being vortexed for 10 min, the mixture was centrifuged at 14 000 g for 10 min. The aqueous phase was transferred to a new tube, and extracted with a mixture of equal volume of phenol/chloroform for 1 min, and centrifuged at 4000 g for 10 min. The extraction was repeated twice. The supernatant was transferred to a new tube containing isopropanol (two-thirds the volume of supernatant), then gently mixed at room temperature for 10 min, and centrifuged at 14 000 g for 10 min. After pouring off and being dried in air, the obtained pellet was suspended in 0.3 mL TE buffer (50 mM Tris-HCl, 10 mM EDTA, pH 8.0), then stored at −20 °C for 1 h after adding 0.2 mL 5 M NaCl and 1 mL frozen ethanol. The obtained DNA was precipitated by centrifugation at 14 000 g for 15 min and washed twice with 75% ethanol, then re-suspended in 50 μL TE buffer. The DNA was qualified and quantified by agar electrophoresis and spectrophotometrics, as described by Sambrook & Russell (2001).