Invasive hyphal growth: An F-actin depleted zone is associated with invasive hyphae of the oomycetes Achlya bisexualis and Phytophthora cinnamomi

A pressure gradient facilitates mass flow in the oomycete Achlya bisexualis

“…Upon impalement, some hyphae reacted with a rapid wound response, resulting in the formation of a plug of cellular material. Pressure readings from hyphae exhibiting a wound response or that gave any indication of a plugged or partially plugged micropipette were discarded (as described by Walker et al, 2006). Growth of the mycelia, measured by the distance from the central divider to the furthest edge of the mycelia, was significantly greater (Pv0.05, Student's t-test) on the 0 M sorbitol side of the split Petri dish than the 0.3 M sorbitol side.…”

“…Stock cultures of the oomycete A. bisexualis Coker (a female strain isolated in New Zealand from Xenopus laevis dung and available from the University of Canterbury culture collection) were maintained on peptone-yeast extractglucose (PYG) containing (%, w/v) peptone (0.125), yeast extract (0.125), glucose (0.3) and agar (2) that had been overlaid with sterile cellophane, as described previously (Walker et al, 2006). The cellophane was washed in three changes of boiling water to remove manufacturing residues.…”

“…A base pressure reading was taken before the micropipette was inserted into a hypha and upon entry a meniscus appeared and shifted part way up the pipette tip; the pressure that needed to be applied to force the meniscus back down to the tip of the pipette was taken as the turgor pressure of the hyphae. Any measurement where there was evidence of a wound response in the hypha was discarded as described by Walker et al (2006).…”

Isolation and Sequencing of Actin1, Actin2 and Tubulin1 Genes Involved in Cytoskeleton Formation in Phytophthora cinnamomi

“…Cell wall was observed by staining with calcoflúor white ( Figure 1B) who indicated the lack division septa and actin cytoskeleton and according to [1]. Actin citoskeleton was visualized with rhodamin-phalloidin, although actin distribution can be observed throughout all the mycelium, appeared more concentrated at the hyphae extremities and adjacent to the plasma membrane ( Figure 1C), according to [7]. In oomycetes actin forms a cap immediately after the apical plasma membrane, whereas in other organisms like P. cinnamomi, the actin appears in small plates in the tips of hyphae [7].…”

“…These properties, together with the actin capacity to carry out the transition between monomeric (G-actin) and filamentous (F-actin) states under the control of nucleotide hydrolysis, ions, and a large number of actin-binding proteins, make actin a critical player in many cellular functions, ranging from cell motility and the maintenance of cell shape and polarity to the regulation of transcription [6,7]. In vertebrates there are three groups of actin isoforms: alpha, beta and gamma.…”