Microtubule dynamics in compatible and incompatible interactions of soybean hypocotyl cells with Phytophthora sojae

Abstract

The arrangement of microtubules in soybean ( Glycine max ) cells was examined during compatible and incompatible interactions of hypocotyls of soybean cv. Harosoy (susceptible) and cv. Haro 1272 (resistant) with race 1 of the soybeanspecific pathogen Phytophthora sojae . Both reaction types were similar during the first 3 h after zoospore inoculation in terms of the number of cells penetrated, and depth penetrated into the cortex. By 3 h postinoculation, clear differences had developed between the two interaction types: incompatible interactions were characterized by a hypersensitive response that was confined to single penetrated cells; while compatibly responding cells appeared unchanged. Both types of response were characterized by autofluorescence of cell walls or cytoplasm and, at 6 h after inoculation, complete disorganization of cell cytoplasm. Reorientation and loss of microtubules was seen in the early stages of the incompatible interaction in association with cellular hypersensitivity, but not in compatible responses. In cells adjacent to those that reacted hypersensitively, there was little evidence of change in microtubule orientation. Treatment of hypocotyls with the microtubule depolymerizer oryzalin prior to inoculation did not alter the compatible response, but led to breakdown of the incompatible response. Changes in microtubule orientation and state are thus among the first structural changes that are visible within cells during incompatibility in this system.

Organisation and regulation of the cytoskeleton in plant programmed cell death

“…42,43 Microtubule organisation is also affected by defence responses, but the response is variable. Disruption and apparent depolymerisation of the microtubule network at the penetration site has been observed in several systems (Figure 1n), 39,40,44 and it has been suggested that this might be an early sign of the HR. 39,42 In other studies microtubules, like F-actin, concentrate at the infection site and undergo bundling, 42 but some studies 43 found no changes in the microtubule organisation upon pathogen attack.…”

The Cytoskeleton as a Regulator and Target of Biotic Interactions in Plants

“…2, A and B). In barley-Erysiphe and flax-Melampsora interactions, radial arrays of microtubules form beneath the appressorium (Kobayashi et al, 1992(Kobayashi et al, , 1994, while in parsley (Petroselinum crispum)-or soybean (Glycine max)-Phytophthora sojae interactions, localized microtubule depolymerization has been observed (Gross et al, 1993;Cahill et al, 2002). In nonhost, incompatible, and compatible interactions of Arabidopsis with P. sojae or different races of Peronospora parasitica, there is neither focusing nor large-scale disappearance of microtubules at the infection site, although diffuse GFP-tubulin fluorescence and a circumferential alignment of microtubules across cell boundaries are observed around the penetration site (Takemoto et al, 2003).…”

Microtubules Are a Target for Self-Incompatibility Signaling in Papaver Pollen

“…These interactions generally involve reorganization and/or focusing of the microtubule cytoskeleton around the infecting organism. However, rapid apparent depolymerization of microtubules has also been reported, for example, in parsley (Petroselinum crispum)-and soybean (Glycine max)-Phytophthora interactions and in elicitor-treated tobacco (Nicotiana tabacum) cells (Gross et al, 1993;Binet et al, 2001;Cahill et al, 2002). Nod factor signaling also stimulates rapid localized apparent depolymerization of microtubules in root hairs and later increases in microtubule arrays (Timmers et al, 1999;Weerasinghe et al, 2003).…”