Woronin body is an organelle specifically found in Euascomycetes that plugs septal pore upon hyphal injury. HEX-1 protein is the major protein in Woronin body and has peroxisome targeting signal 1 (PTS1) at the C-terminus. This suggests that Woronin body is a specialized class of the peroxisome. However, not much is known at the molecular level how Woronin body is differentiated from the peroxisome. In this report, we investigated the role of AoPex11, a peroxisomal membrane protein required for peroxisome proliferation, in formation and function of Woronin body in Aspergillus oryzae. According to the genome database, A. oryzae contains two PEX11 homologous genes (named as Aopex11-1 and Aopex11-2). We deleted these Aopex11 genes in the A. oryzae Ku70-deficient strain, and only the Aopex11-1 deleted mutant showed reduced growth in the presence of oleic acid as carbon source, revealing a defect in peroxisome function. Expression of the EGFP-PTS1 construct visualizing the peroxisome in the Aopex11-1 deletion background showed a limited number of enlarged peroxisomes, while the control strain had various sizes of this organelle. Simultaneous expression of the mDsRed-AoHex1 fusion protein demonstrated that the deletion mutant contained fewer independent Woronin bodies. Moreover, distribution of AoHex1 was found to be peripheral in the enlarged peroxisome or junctional inside the dumbbell-shaped peroxisome, suggesting immature Woronin bodies inside the peroxisome. Consistently, hyphal tip bursting experiment induced by hypotonic shock revealed that only the Aopex11-1 deleted mutant partially lacked normal Woronin body function. These data indicate that AoPex11-1 involved in peroxisome proliferation plays a role in Woronin body differentiation from the peroxisome.
Full conference title:
9th EUROPEAN CONFERENCE ON FUNGAL GENETICS
- ECFG 9th (2008)