Impact of a golgi-located protein involved in secretion on morphogenesis of the filamentous fungus Aspergillus oryzae

Jun-ya Shoji, Ayako Taura, Manabu Arioka, Katsuhiko Kitamoto

Author address: 

Department of Biotechnology, The University of Tokyo, Tokyo, Japa

Abstract: 

Continuous tip growth of filamentous fungi is achieved by establishment of polarity axis that modulates proper organization of cytoskeleton and subsequent polarized secretion. Polarized secretion of filamentous fungi is also crucial for progress of industrial production of useful proteins. However, our understanding of vesicular trafficking and secretion in filamentous fungi has been too fragmentary. In our previous study, we observed intracellular distribution of enhanced green fluorescent protein (EGFP)-fused soluble NSF attachment protein receptors (SNAREs) in Aspergillus oryzae. Among the fusion proteins, overexpression of EGFP-fused AoSed5p, a Golgi target (t)-SNARE, resulted in pleiotropic defects in hyphal growth. These defects were not attributed to the fusion with EGFP, and overexpression of AoSed5p alone resulted in similar phenotype. Although overexpression of Sed5p in the budding yeast causes a growth defect as well, defects observed in A. oryzae were much more drastic. In the presence of excess AoSed5p, tip growth was severely impeded. Conidia and hyphal tips often swelled, and showed abnormal dichotomous-like branching. These results suggest that the overexpression of AoSed5p causes defective polarized growth. In addition, the overexpression of AoSed5p resulted in accumulation of nuclei, fragmentation of vacuoles, and accumulation of chitin at the cell wall. It also caused aberrant organization of actin and microtubules. In the budding yeast, overexpression of a phosphorylated state of Sed5p inhibits retrograde transport from Golgi to endoplasmic reticulum while a dephosphorylated state does not. We then overexpressed similar phosphorylated/dephosphorylated states of AoSed5p in A. oryzae and found that the phosphorylated state of AoSed5p is responsible for the above-mentioned growth defects. These results suggest that the Golgi t-SNARE AoSed5p, and probably secretion, play vital roles in hyphal morphogenesis, through feedback regulation on cellular polarity and cytoskeleton
2008

abstract No: 

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Full conference title: 

9th EUROPEAN CONFERENCE ON FUNGAL GENETICS
    • ECFG 9th (2008)