Evidence for an inositol lipid signal pathway in the yeast-mycelium transition of Ophiostoma ulmi, the Dutch elm disease fungus

TY - JOUR

T1 - Evidence for an inositol lipid signal pathway in the yeast-mycelium transition of Ophiostoma ulmi, the Dutch elm disease fungus

AU - Brunton, A. H.

AU - Gadd, G. M.

N1 - Copyright © 1991 British Mycological Society. Published by Elsevier Ltd. All rights reserved.

PY - 1991/4

Y1 - 1991/4

N2 - Results presented in this paper indicate the involvement of an inositol lipid signalling system, including protein kinase C, in the yeast-mycelium transition of Ophiostoma ulmi. The exogenous supply of inositol 1,4,5-trisphosphate (Inauthor,4,5P3) induced germ tube formation in O. ulmi, maximum germ tube formation resulting at a concentration of 30 μm. The addition of Inauthor,4,5P3 10 min after initiation of Ca2+ uptake by non-growing yeast cells of O. ulmi resulted in a slight increase in Ca2+ uptake. The protein kinase C-activating phorbol ester, phorbol 12-myristate 13-acetate (PMA), also induced a significant germination response in O. ulmi and approximately 50% of the population exhibited germ tube formation after 12 h incubation in the presence of 16 nm-PMA. This indicated a possible role for protein kinase C, and therefore diacylglycerol, in the germination response. Ca2+ uptake by yeast extract-(1% w/v) induced germ tubes of O. ulmi was slower than that which occurred in PMA- or Inauthor,4,5P3-induced germ tubes under similar conditions, PMA-induced germ tubes showing the highest levels of Ca2+ uptake. The anti-calmodulin drug R24571, at 3 μm, caused almost complete suppression of a yeast extract-induced yeast-mycelium (Y-M) transition which confirmed the involvement of calmodulin in germ tube formation. The addition of 16 nm-PMA in conjunction with yeast extract had no effect on germ tube formation yet, when added with R24571, the inhibitory effect of R24571 was reversed and an almost complete Y-M transition resulted after 16 h incubation. This provided further evidence that activation of protein kinase C was required for germ tube formation in O. ulmi. Ca2+ uptake by yeast cells or during the growth of yeast extract- and PMA-induced germ tubes of O. ulmi increased markedly over the first 12 h of growth with highest Ca2+ uptake occurring in yeast extract-induced germ tubes. Ca2+ uptake by 12 h yeast cells of O. ulmi was inhibited after preincubation for 10 min with PMA suggesting either inhibition of Ca2+ influx or stimulation of Ca2+ efflux. Use of Ca2+-loaded cells showed that efflux of Ca2+ from Ca2+-loaded yeast cells of O. ulmi was similar in the absence or presence of 70 mm glucose but increased rapidly on addition of PMA to the incubation medium.

AB - Results presented in this paper indicate the involvement of an inositol lipid signalling system, including protein kinase C, in the yeast-mycelium transition of Ophiostoma ulmi. The exogenous supply of inositol 1,4,5-trisphosphate (Inauthor,4,5P3) induced germ tube formation in O. ulmi, maximum germ tube formation resulting at a concentration of 30 μm. The addition of Inauthor,4,5P3 10 min after initiation of Ca2+ uptake by non-growing yeast cells of O. ulmi resulted in a slight increase in Ca2+ uptake. The protein kinase C-activating phorbol ester, phorbol 12-myristate 13-acetate (PMA), also induced a significant germination response in O. ulmi and approximately 50% of the population exhibited germ tube formation after 12 h incubation in the presence of 16 nm-PMA. This indicated a possible role for protein kinase C, and therefore diacylglycerol, in the germination response. Ca2+ uptake by yeast extract-(1% w/v) induced germ tubes of O. ulmi was slower than that which occurred in PMA- or Inauthor,4,5P3-induced germ tubes under similar conditions, PMA-induced germ tubes showing the highest levels of Ca2+ uptake. The anti-calmodulin drug R24571, at 3 μm, caused almost complete suppression of a yeast extract-induced yeast-mycelium (Y-M) transition which confirmed the involvement of calmodulin in germ tube formation. The addition of 16 nm-PMA in conjunction with yeast extract had no effect on germ tube formation yet, when added with R24571, the inhibitory effect of R24571 was reversed and an almost complete Y-M transition resulted after 16 h incubation. This provided further evidence that activation of protein kinase C was required for germ tube formation in O. ulmi. Ca2+ uptake by yeast cells or during the growth of yeast extract- and PMA-induced germ tubes of O. ulmi increased markedly over the first 12 h of growth with highest Ca2+ uptake occurring in yeast extract-induced germ tubes. Ca2+ uptake by 12 h yeast cells of O. ulmi was inhibited after preincubation for 10 min with PMA suggesting either inhibition of Ca2+ influx or stimulation of Ca2+ efflux. Use of Ca2+-loaded cells showed that efflux of Ca2+ from Ca2+-loaded yeast cells of O. ulmi was similar in the absence or presence of 70 mm glucose but increased rapidly on addition of PMA to the incubation medium.

UR - https://www.scopus.com/pages/publications/0000151505

U2 - 10.1016/S0953-7562(09)80850-2

DO - 10.1016/S0953-7562(09)80850-2

M3 - Article

AN - SCOPUS:0000151505

SN - 0953-7562

VL - 95

SP - 484

EP - 491

JO - Mycological Research

JF - Mycological Research

IS - 4

ER -