Eiko Tsuchiya

Structure of rhodotorucine A, a novel lipopeptide, inducing mating tube formation in Rhodosporidiumtoruloides

Abstract Rhodotorucine A is a peptidyl factor which induces mating tube formation in Rhodosporidium toruloides . The amino acid sequence of the factor was determined by Edman degradation and enzymatic hydrolysis. Rhodotorucine A was shown to contain a lipophilic amino acid, S-farnesyl cysteine, at C-terminus by proton magnetic resonance, mass spectrometry and chemical synthesis. We proposed the following structure for rhodotorucine A . H-Tyr-Pro-Glu-Ile-Ser-Trp-Thr-Arg-Asn-Gly-Cys(S-farnesyl)-OH

Requirements of chemical structure for hormonal activity of lipopeptidyl factors inducing sexual differentiation in vegetative cells of heterobasidiomycetous yeasts

Biological activities of both peptidyl and isoprenyl constituents of yeast sex hormones (lipopeptides), rhodotorucine A and farnesyl tremerogen A -10, were examined. The chemically synthesized simple peptides (peptidyl constituents) and farnesyl cystein (isoprenyl one) did not exhibit any biological activities, such as hormonal and hormone-inhibitory (or -accelerative) activities. The mixture of both constituents also had no activity. Then, it is assumed that the heterobasidiomycetous yeasts ( Rhodosporidium toruloides and Tremella mesenterica ) recognize the total structure of lipopeptidyl molecule for the biological response, sexual differentiation, and the term “Pattern Recognition” is proposed for the mode of this recognition.

Binding of rhodotorucine A, a lipopeptidyl mating hormone, to a cells of Rhodosporidium toruloides for induction of sexual differentiation.

Rhodotorucine A , a lipopeptidyl mating hormone, selectively bound to the cells of Rhodosporidium toruloides M-1057, mating type a , having a large number of hormone-binding site, approximately 5 × 10 7 molecules per cell. The binding is temperature-independent. The bound hormone is sensitive to pronase, while the binding site is resistant to the protease. The cells, which were preincubated with the hormone at 25°C for 10 min (10-min hormone-preincubation), completely lost the mating tube-forming ability by pronase treatment, while the cells of 15-min hormone-preincubation remained the ability after the treatment. Thus, it is concluded that the establishment of intracellular information inducing sexual differentiation depends on the term of preincubation, such as 15 min, with the hormone at 25°C.

An electron microscopic study on the mating tube formation in the heterobasidiomycete Tremella mesenterica

Ultrastructure of the mating tube formed in yeast haplont of the heterobasidiomycete Tremella mesenterica was studied by electron microscopy. Cell wall of the mating tube emerged as evagination of the inner layers, rupturing outer layers of the mother cell wall. Comparison with budding cells suggested that the tube emergence place at bud scar and the process of tube emergence was the same as that of bud emergence. Electron transparent vesicles of 0.1 μm diameter were scattered in the cytoplasm of the mating tube. Nucleus-associated organelle was located at one side of the nuclear envelope which extended towards the mating tube. A few microtubules were detected in the mating tube, but their association with a nucleus was not clear. The cytoplasmic structure of the mating tube was discussed in comparison with that of hyphae of the filamentous fungi.