e. FgGFP1 (male) × Z3643 (female)]. Availability of individual MAT

transcript expression profiles in various fungal strains provides clues to the variation in self-fertility among the Fg complex at the level of MAT loci. The differing expression pattern of individual MAT genes in all F. asiaticum strains compared with F. graminearum strains can be attributable to the defect in self-fertility in these strains. Failure to up-regulate MAT1-1-2 and MAT1-1-3, and reduced up-regulation of MAT1-1-1, MAT1-2-1, and MAT1-2-3 during the entire sexual cycle may cause a putative set of genes under the control of these MAT genes to be abnormally or not properly expressed, leading to self-sterility in F. asiaticum. Nevertheless, similarity in expression patterns of MAT1-1-1, MAT1-2-1, GKT137831 molecular weight and MAT1-2-3 in all F. graminearum and F. asiaticum strains

examined cannot exclude the possibility that the early induction pathway of sexual development controlled by these genes is PI3K inhibitor not responsible for the self-fertility differences in these Fg complex strains. To test these postulates, a comparison of genome-wide expression profiles using combinations of wild-type F. graminearum and F. asiaticum strains and their MAT-deleted strains would be necessary. To date, several approaches have been used to identify the target genes of MAT loci in several filamentous fungi (Qi et al., 2006; Hallen et al., 2007; Keszthelyi et al., 2007; Klix et al., 2010; Bidard et al., 2011). For example, comparing transcription profiles during sexual development, or between a fertile fungal strain and its transgenic strain lacking a MAT gene (e.g. in P. anserina, F. verticillioides, Beta adrenergic receptor kinase and S. macrospora), provided several sets of genes

differentially regulated in the mutant strains. However, the genes directly regulated by individual MAT genes remain undetermined. The developmental up-regulation pattern and transcript abundance in two sets of MAT genes (a set of MAT1-1-1, MAT1-2-1, and MAT1-2-3, and the other of MAT1-1-2 and MAT1-1-3) provide new insight into functional role(s) of individual MAT genes for sexual development in F. graminearum, which are also supported by the phenotypic changes in the gene deletion strains. The former set of MAT genes can be considered key regulators of sexual development, particularly required for the early sexual stage for the following reasons. First, the gene expressions peaked at 2 dai, and the transcripts were more (at least 65-fold higher) abundant than those of the latter set of MAT genes at 2 dai. Secondly, the absence of perithecium-like structures in ΔMAT1-2-1 strain or the presence of barren perithecia in the ΔMAT1-1-1 strain, which were even smaller than those in the ΔMAT1-1-2 and ΔMAT1-2-3 strains, on carrot agar could be attributable to blockage of early events such as internuclear recognition, formation of ascogenous hyphae, and nuclear fusion.