Accumulation of photoassimilate by Peronospora viciae (Berk.) Casp. and leaves of Pisum sativum L.: evidence for nutrient uptake via intercellular hyphae

Abstract

SUMMARYAutoradiography showed that accumulation of label by hyphae of Peronospora viciae (Berk.) Casp., in leaflets of Pisum sativum L. exposed to '*CO,^, was up to 4-5 times greater in the susceptible cv. Krupp Pelushka than the resistant cv. Early Onward. Concentrations of label were similar in apoplastic solutions from both cvs, although a greater volume was available in Early Onward. Uninfected Krupp Pelushka assimilated more label from '*CO,t han Early Onward; /)ara-chloro-niercuribenzene sulphonic acid (PCMBS) treatment and infection reduced assimilation by Krupp Pelushka but not Early Onward, Infected leaf tissue from Early Onward assimilated more label than Krupp Pelushka from ['''C]sucrose supplied to the apoplast. Transient treatment with PCMBS reduced assimilation of ['^C]sucrose into infected plant tissue to 30 and 61 % of untreated levels, in Early Onward and Krupp Pelushka respectively. In contrast, autoradiography of hyphal fragments showed that the fungus accumulated 1-4 times more label from ["C]sucrose than without PCMBS. The different nutrient status of leaves of Early Onward and Krupp Pelushka, and evidence that label from sucrose is accumulated by intercellular hyphae directly from the apoplast, are discussed in relation to the role of haustoria and mechanisms of compatibility.

The mode of interaction between Vitis and Plasmopara viticola Berk. & Curt. Ex de Bary depends on the host species

“…It remains to be elucidated how the hyphae that do not penetrate through the stomata can withdraw the necessary carbohydrates from the apparently intact leaf, and we know of no case of such a saprotrophic Peronosporomycete. However, it should be mentioned that hyphae of the related Peronospora viciae have been shown to be capable of direct photoassimilate uptake (Clark & Spencer‐Phillips 1993) and can accumulate glucose in vitro (El‐Gariani & Spencer‐Phillips 2004). However, in our experiments these mycelia were observed on leaf discs under artificial conditions with very high humidity, i.e .…”

Exploring Infection of Wheat and Carbohydrate Metabolism in Mycosphaerella graminicola Transformants with Differentially Regulated Green Fluorescent Protein Expression

“…In ectotrophic fungi, nutrient transfer is thought to involve specialized intercellular hyphae (Hardham 1992), described by Heath and Skalamera (1997) as "conspicuously wider than those growing nonbiotrophically in the same plant." Evidence for fungal structure-dependent nutrient uptake has been obtained from pulse-chase experiments carried out with 14 CO 2 (Clark and Spencer-Phillips 1993;Manners and Gay 1982). Results obtained by this method, however, give only a fragmented picture of the time course of nutrient transfer during infection, which cannot be related confidently to fungal structures localized inside the host.…”

The Compatible Interaction in Downy Mildew Infections

“…There is evidence for case (b), however, in that carbon from sucrose can be transferred to intercellular hyphae when the route via infected host cells and haustoria is blocked by the sucrose transport inhibiter PCMBS (Clark and Spencer-Phillips, 1993). Experiments showing that P. viciae hyphae separated from living plant cells can also accumulate label from glucose (El-Gariani and Spencer-Phillips, this volume) adds to this evidence.…”

“…At 2 days post inoculation, hyphal length and haustorial frequency in the susceptible cv was 2.4 and 4.8 fold greater respectively than in the resistant cv, and by 4 days this had increased to 10.2 fold for hyphal length and 10.6 fold for haustoria, as indicated in Figure 2. At six days post-inoculation, hyphae had accumulated 4.2 times more ethanol-insoluble label from 14 CO 2 supplied to infected leaves in the susceptible than in the resistant cv (Clark and Spencer-Phillips, 1993).…”