## 4 Discussion
### Investigation of Morphological Changes during Biotrophic Mycoparasitism  
Previously, monitoring shifts in Fourier transform infrared (FTIR) molecular signatures combined with scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) assessments at the fungus-fungus (_Sphaerodes-Fusarium_) interface has proven to be a useful tool for detecting early mycoparasitism-related interactome (proteins, lipids, and  
Figure 10: Phylogenetic tree for SmBub2 mitotic check point protein in _S. mycoparasittica_ incubated for 1.5 days in interaction with _Fusarium graninearum_ 3-ADON host. The branch support bootstrap values were obtained by 1000 replicates using the NJ method. carbohydrates etc.) as a vital asset of the preventive biocontrol strategy against Fusarium pathogens [32]. Based on TEM analysis conducted in this study, it appears that _S. myxoparasitica_ utilizes a specialized host-infecting structure, an appressorium/haustorium type structure. Thus, the lifestyles of _S. myxoparasitica_ with _Fusarium_ hosts belong to biotrophic parasitism and possess infection structures similar to biotrophic fungi (within ascomycetes) such as _Blumeria graminis_, _Erysiphe pisi_, _Golovinomyces corontii_, and _Magnoportha oryzae_, with mechanisms for the direct uptake of nutrients [49; 50; 51; 52]. Another interesting feature during the biotrophism was also noticed. Indeed, Sm developed an infection structure called the appressorium to penetrate the host cells. The ABC-type glutathione-_S_-conjugate and the SmBub2 (non-ABC) genes were upregulated in tandem at 1.5 days which coincided with the appressorium formation on the host cell surface. The mitotic checkpoint protein Bub2 gene is a regulator of appressorium formed by germ tubes and appressorium-like structures developed by hyphal tips as observed in _Magnaporthe oryzae_[53; 54]. In addition, the observed mucosa-like substance on cell surfaces, such as mucins, may act as barriers and sensors of the extracellular environment including the changes in pH, ionic composition, or physical interactions [55]. Mucins and mucin-like molecules are present in the cell surfaces of eukaryotes in the form of highly _O_-glycosated proteins [56]. On the basis of the structure, function, and cellular localization of mucin proteins, mucins are classified into two categories, i.e., secreted mucins and membrane (cell surface-associated) mucins [57]. In _M. oryzae_, _Msb2_ was reported to be a cell surface (signaling) mucin gene and the _Momsb2_ mutant showed a significant reduction in appressorium formation on hydrophobic surfaces [58]. In the transcriptome of _S. myxoparasitica_, _Msb2_ was also found (data not shown). Importantly, the early stage of the interactive transcriptome of _S. myxoparasitica_ showed upregulated transcripts annotated to MUC 5 AC, one of the secreted gel-forming mucins (MUC 2, MUC 5 AC, 5B, 6, and 19) [57]. In addition, biotrophy-associated secreted (BAS) proteins of _Magnaporthe oryzae_ are distinctive plant pathogenic features [59]. Studying _M. oryzae_ as a model chemibotrophic system, [PERSON] et al. (2009) demonstrated the localization of fluorescently labeled BAS proteins [60]. In fact, the accumulation of BAS1 and BAS2 was preferentially into biotrophic interfacial complexes along with known ariulence effectors. The localization of BAS3 was situated near cell wall crossing points, while the formation of a line of BAS4 was uniformly on growing invasive hyphae [60]. In this study, _S.m._ showed two different transcripts annotated to biotrophy-associated secreted (BAS) proteins. The phylogenetic analysis of the transcript Sm68082_c0_g1_i1 annotated to BAS2 showed relatively close relationships with saprophytic and endophytic fungus _P. comata_ followed by hemibiotrophic fungus _C. orchidophilum_ phylogenetically. The function of the transcript seemed to be focused on biotrophy due to the abundant appearance of BAS2. Within the same genus _Colletotrichum_, it has been demonstrated that BAS2, identified in _C.