UV MICROIRRADIATION IMPLICATES F-ACTIN IN REINFORCING GROWING HYPHAL TIPS

Citation
Sl. Jackson et Ib. Heath, UV MICROIRRADIATION IMPLICATES F-ACTIN IN REINFORCING GROWING HYPHAL TIPS, Protoplasma, 175(1-2), 1993, pp. 67-74
Citations number
47
Categorie Soggetti
Cytology & Histology
Journal title
ISSN journal
0033183X
Volume
175
Issue
1-2
Year of publication
1993
Pages
67 - 74
Database
ISI
SICI code
0033-183X(1993)175:1-2<67:UMIFIR>2.0.ZU;2-4
Abstract
The cell walls of plants and fungi are thought to provide the strength required to resist turgor and thus maintain the integrity and morphol ogy of these cells. However, during growth, walls must undergo rapid e xpansion which requires them to be plastic and therefore weak. In most tip-growing cells there is an apical concentration of F-actin associa ted with the rapidly expanding cell wall. Disruption of F-actin in the growing tips of hyphae of Saprolegnia ferax by a localized irradiatio n, beginning 2-6 mum behind the apex, with actin-selective 270 nm uv l ight caused the hyphae to burst, suggesting that actin supports the we ak apical wall against turgor pressure. Bursting was pH dependent and Ca2+ independent at neutral pH. Hyphae burst in the very tip, where th e cell wall is expected to be weakest and actin is most concentrated, as opposed to the lower part of the apical taper where osmotic shock i nduces bursting when actin is intact. When hyphae were irradiated with a wavelength of light that is less effective at disrupting actin, gro wth was slowed but they failed to burst, demonstrating that bursting w as most likely due to F-actin damage. We conclude that F-actin reinfor ces the expanding apical wall in growing hyphae and may be the prime s tress bearing structure resisting turgor pressure in tip growing cells .