Polarized gene expression determines woronin body formation at the leading edge of the fungal colony.
The Woronin body (WB) is a peroxisome-related organelle that is centered on a crystalline core of the HEX-1 protein, which functions to seal septal pores of filamentous ascomycetes in response to cellular damage. Here, we investigate the cellular and genetic control of WB-formation and show that polarized hex-1 gene expression determines WB-biogenesis at the growing hyphal apex. We find that intron splicing is coupled to efficient hex-1 gene expression and strikingly, when the yellow fluorescent protein was expressed from hex-1 regulatory sequences, we observed a fluorescent gradient that was maximal in apical cells. Moreover, endogenous hex-1 transcripts were specifically enriched at the leading edge of the fungal colony, whereas other transcripts accumulated in basal regions. Time-lapse confocal microscopy showed that HEX-1 crystals normally formed in the vicinity of the hyphal apex in large peroxisomes, which matured and were immobilized at the cell periphery as cells underwent septation. When the hex-1 structural gene was expressed from regulatory sequences of an abundant, basally localized transcript, WB-core formation was redetermined to basal regions of the colony, and these strains displayed loss-of-function phenotypes specifically in apical hyphal compartments. These results show that apically localized gene expression is a key determinant of spatially restricted WB-assembly. We suggest that this type of regulation may be widely used to determine cellular activity in apical regions of the fungal hypha.
Tey
Wei Kiat
WK
Comparative Cell Biology Group, Temasek Life Science Laboratory, National University of Singapore, Singapore 117604, Singapore.
North
Alison J
AJ
Reyes
Jose L
JL
Lu
Yan Fen
YF
Jedd
Gregory
G
D016764:Cell Polarity; D005456:Fluorescent Dyes; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D025301:Hyphae / Q000166:cytology / Q000254:growth & development; D007438:Introns; D018613:Microscopy, Confocal; D018715:Microscopy, Video; D009492:Neurospora crassa / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D015388:Organelles / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020675:Peroxisomes / Q000378:metabolism; D014158:Transcription, Genetic
D005456:Fluorescent Dyes; D005656:Fungal Proteins; C426803:Woronin body major protein, Neurospora crassa