rodletless mutants of Aspergillus fumigatus

Abstract

Conidia of Aspergillus fumigatus adhere in vitro to host proteins and cells via the outer cell wall layer. The rodA gene ofA. fumigatus was cloned by homology with the rod4 gene ofAspergiUlus nidulans, which is involved in the structure of the rodlets characteristic of the surface layer. The A.fumigatus RODA protein sequence has 85% similarity to that of A. nidulans RODA; the sequence codes for a hydrophobin, a low-molecular-weight protein moderately hydrophobic and rich in cysteines. The gene was disrupted with the hygromycin B resistance gene. By transformation of protoplasts with the disrupted gene, RodAmutants were generated. These mutants are deficient in the ability to disperse their conidia; their conidia lack the rodlet layer and are hydrophilic. The adhesion of the rodletless conidia to collagen and bovine serum albumin was lower than that of the wild type; in contrast, there was no difference between RodAand RodA+ conidia in adhesion to pneumocytes, fibrinogen, and laminin, suggesting that RODA is not the receptor for these cells and proteins. RodAconidia were pathogenic for mice.

The fungal hydrophobin RolA recruits polyesterase and laterally moves on hydrophobic surfaces

“…We found that transcription of certain genes was specifically upregulated in cells grown in CD-PBSA but not in cells grown in CD-SU (succinate) or CD-BU (1,4-butanediol). Two specific genes were observed from the microarray analyses: one is an orthologue of the A. nidulans rodA gene, which codes for a RodA-like biosurfactant protein ( E -value 4e-57 to A. nidulans rodlet protein precursor, 9e-57 to Aspergillus fumigatus hydrophobin precursor) (Stringer et al ., 1991;Thau et al ., 1994); and the other has not yet been assigned, although we searched the BLAST network service. Thus, we studied the identified gene, which we refer to as the A. oryzae rolA gene.…”

The molecular mechanisms of conidial germination

“…Conidia adhere to extracellular matrix proteins, such as ¢bronectin, collagen and laminins, that are found in host tissue. A 72-kDa cell wall laminin-binding protein has been isolated from A. fumigatus conidia [29]. Deletion of the rodA gene, which encodes a hydrophobin involved in the structure of the outer rodlet layer of conidia, decreased adherence to collagen but not to laminin and ¢brinogen [30].…”

Detection of early phase specific surface appendages during germination of Aspergillus fumigatus conidia

“…However, under conditions that triggered germination we also detected conidia with a size that was comparable to that of resting conidia having already lost their echinulate morphology. These cells showed a phenotype that resembles that of smooth mutants that lack essential components of the rodlet layer [10,13,14].…”

“…Due to a layer of hydrophobic proteins, called hydrophobins, resting conidia of A. fumigatus show an echinulate surface morphology, that is organized as interwoven rodlet fascicles. Disintegration of this surface layer during germination has been shown [12] and several mutants have been described that lost this characteristic morphological feature, resulting in a smooth surface [10,13,14]. Interestingly most of these mutants were shown to be impaired in virulence in an immuno-suppressed mouse model, suggesting that the hydrophobic surface layer plays an important role in the infection process of A. fumigatus [13,14].…”