Summary: Mycelial fungi generate endogenous electrical fields which are associated with polarized tip growth. Here we show that applied electrical fields can dramatically affect the polarity of growth of a variety of filamentous fungi including Neurospora crassa, Aspergillus nidulans, Mucor mucedo, Trichoderma harzianum and Achlya bisexualis. The precise behaviour of each fungus when exposed to an electric field was different; however the sites of germ tube formation and branching, the direction of hyphal extension and the frequency of branching and germination could all be affected. N. crassa and Ach. bisexualis grew and formed branches towards the anode while Asp. nidulans and M. mucedo exhibited tropisms towards the cathode. Galvanotropism of hyphae and branches of T. harzianum was in opposite directions. Germ tube formation from conidia of N. crassa was highly polarized in electrical fields whereas fields of a similar strength had little effect on the polarity of germ tube formation in Asp. nidulans. Hyphae became aligned perpendicularly as they grew longer and as the field strength increased. It is suggested that this perpendicularly orientated extension relieves growth-inhibiting perturbations of the membrane potential in cells which had been aligned parallel to the field. These results are discussed in relation to the hypothesis that the polarity of hyphal growth is under electrical control.
ArmbrusterB. L.,
WeisenseelM. H.1983; Ionic currents traverse growing hyphae and sporangia of the mycelial water mould Achlya debaryana. Protoplasma 115:65–69
BrawleyS. H.,
RobinsonK. R.1985; Cytochalasin treatment disrupts the endogenous currents associated with cell polarisation in fucoid zygotes: studies on the role of f-actin in embryogenesis. Journal of Cell Biology 100:1173–1184
CooperM. S.,
KellerR. E.1984; Perpendicular orientation and directional migration of amphibian neural crest cells in DC electrical fields. Proceedings of the National Academy of Sciences of the United States of America 81:160–164
de VriesS. C.,
WesselsJ. G. H.1982; Polarized outgrowth of hyphae by constant electrical fields during reversion of Schizophyllum commune protoplasts. Experimental Mycology 6:95–98
GowN. A. R.,
McgillivrayA. M.1986; Ion currents, electrical fields and the polarized growth of fungal hyphae. In Ionic Currents in Development (Proceedings of a Satellite Meeting to the 10th International Congress of the International Society of Developmental Biologists, University of California, Los Angeles) pp 81–88
GowN. A. R.,
KropfD. L.,
HaroldF. M.1984; Growing hyphae of Achlya bisexualis generate a longitudinal pH gradient in the surrounding medium. Journal of General Microbiology 130:2967–2974
HorwitzB. A.,
WeisenseelM. H.,
DornA.,
GresselJ.1984; Electric currents around growing Trichoderma hyphae, before and after photoinduction of conidiation. Plant Physiology 74:912–916
JaffeL. F.1966; Electrical currents through the developing Fucus egg. Proceedings of the National Academy of Sciences of the United States of America 56:1102–1109
JaffeL. F.,
RobinsonK. R.,
NuccitelliR.1974; Local cation entry and self-electrophoresis as an intracellular localization mechanisms. Annals of the New York Academy of Sciences372–389
KropfD. L.,
LupaM. D. A.,
CaldwellJ. C.,
HaroldF. M.1983; Cell polarity: endogenous ion currents precede and predict branching in the water mold Achlya. Science 220:1385–1387
KropfD. L.,
CaldwellJ. C.,
GowN. A. R.,
HaroldF. M.1984; Transcellular ion currents in the water mold Achlya Amino acid proton symport as a mechanism of current entry. Journal of Cell Biology 99:486–496
ManavathuE. K.,
ThomasD. D. S.1985; Chemotropism of Achlya ambisexualis to methionine and methionyl compounds. Journal of General Microbiology 131:751–756
MillerA. L.,
RavenJ. A.,
SprentJ. I.,
WeisenseelM. H.1986; Endogenous ion currents traverse growing roots and root hairs of Trifolium repens. Plant Cell and Environment 9:79–83
MusgraveA.,
EroL.,
SchefferR.,
OehlersE.1977; Chemotropism of Achlya bisexualis germ hyphae to casein hydrolysate and amino acids. Journal of General Microbiology 101:65–70
NuccitélliR.1978; Ooplasmic segregation and secretion in the Pelvetia egg is accompanied by a membrane-generated electrical current. Developmental Biology 62:13–33