Jw. Buck et Jh. Andrews, Attachment of the yeast Rhodosporidium toruloides is mediated by adhesiveslocalized at sites of bud cell development, APPL ENVIR, 65(2), 1999, pp. 465-471
The basidiomycetous yeast Rhodosporidium toruloides (anamorph, Rhodotorula
glutinis) is a common phylloplane epiphyte with biocontrol potential. To un
derstand how R. toruloides adheres to plant surfaces, we obtained nonadhere
nt fungal mutants after chemical mutagenesis with methane-sulfonic acid eth
yl eater. Sixteen attachment-minus (Att(-)) mutants were identified by thre
e methods: (i) screening capsule-minus colonies for loss of adhesive abilit
y; (ii) enrichment for mutants unable to attach to polystyrene; and (iii) s
election for reduced fluorescence of fluorescein isothiocyanate-concanavali
n A (Con A)-stained cells by fluorescence-activated cell sorting. None of t
he 16 mutants attached to polystyrene or barley leaves. The lectin Con A el
iminated adhesion in all of the wild-type isolates tested. Hapten competiti
on assays indicated that Con A bound to mannose residues on the cell surfac
e. Adhesion of wild-type R. toruloides was transient; nonadhesive cells sub
sequently became adhesive, with bud development, All Att(-) mutants and non
attaching wild-type cells lacked polar regions that stained intensely with
fluorescein isothiocyanate-Con A and India ink. Lectin, enzyme, and chemica
l treatments showed that the polar regions consisted of alkali-soluble mate
rials, including mannose residues. Tunicamycin treatment reduced wild-type
adhesion, indicating that the mannose residues could be associated with gly
coproteins, We concluded that compounds, including mannose residues, that a
re localized at sites of bud development mediate adhesion of R. toruloides
to both polystyrene and barley leaf surfaces.