, 1996). This response is similar to that observed in plants (Tasaka et al., 2001). Gravitropism in higher fungi has been studied for over 100 years, and the clear association between gravitropism and the onset of sporulation implies that both meiosis and sporulation which are coupled to fruiting body SB203580 datasheet growth seem to require the gravity force (Moore,

1991). An experiment performed under real microgravity conditions in orbit suggests that gravity may be required for the initiation of fruiting in the fungus Polyporus brumalis (Moore, 1991; Zharikova et al., 1977). However, there is no convincing evidence regarding the graviperception mechanism in fungi. To understand the molecular mechanisms of gravitropism, particularly during fruiting body formation in fungi, we attempted to isolate differentially expressed genes from the fruiting bodies of the fungus Pleurotus ostreatus (oyster mushroom) cultivated under simulated microgravity conditions using a three-dimensional (3D) clinostat. Fruiting body development in P. ostreatus, one of the most popular

edible mushrooms cultivated in the world (Chang & Miles, 1991), results from the aggregation of vegetatively growing mycelia on sawdust –rice bran medium with formation of primordia that progressively grow into mature fruiting bodies (Zedrazil, 1978). A 3D clinostat is an apparatus that nullifies the effect of gravity. It has been used in substitution find protocol studies to examine the effects of microgravity on biological events in ground-based research, particularly in the field of space biology (Grimm et al., 2002; Higashibata et al., 2006; Hirasaka et al., 2005; Li et al., 2002; Sarkar et al., 2000; Uva et al., 2002; Woods et al., 2003). In studies on plants, it has been fully demonstrated Baf-A1 solubility dmso that a 3D clinostat is an effective and valuable device for simulating weightlessness (Hoson et al., 1997). We examined in detail the differential expression of genes in fruiting bodies of

P. ostreatus under clinostat-rotated (simulated microgravity) and static (fixed to the ground) culture conditions. For this purpose, we used a technique of subtractive hybridization mediated by PCR, cDNA representational difference analysis (cDNA-RDA) (Hubank & Schatz, 1994). This is a powerful technique for the detection of differential gene expressions and is sufficient to reflect a large number of relevant gene transcripts in the fruiting bodies of Pleurotus because we have previously succeeded in isolating over 100 developmentally regulated genes that were specifically transcribed during fruiting body formation in the fungus Lentinula edodes (shiitake mushroom) using cDNA-RDA (Miyazaki et al., 2005). Mycelia of the commercial P. ostreatus strain N36 (Mori & Company Ltd) previously cultured in MYG medium (1% malt extract, 0.4% yeast extract, 0.