TRANSPORT, TRANSLOCATION AND METABOLISM OF 14C‐PHOTOSYNTHATES AT THE HOST‐PARASITE INTERFACE OF PISUMSATIVUM AND ERYSIPHE PISI

Abstract

Haustorial complex, mycelial and host (leaf without mycelia) samples were obtained from leaves of Pisum sativum infected with Erysiphe pisi either immediately following a 20 min exposure to 14CO2 (‘pulse’) or after a further 20 h ‘chase’ in 12CO2. After the ‘pulse’, labelled ethanol‐soluble sugars (glucose, fructose and sucrose) and mannitol predominated in the host and mycelial fractions respectively and lipids (mainly triglycerides) and an ethanol‐insoluble glucan (not α‐1, 4 linked) contained most of the 14C in the haustorial complexes. Ethanol‐soluble carbohydrates contained only 3% of the total 14C in the haustorial complexes with sucrose and glycerol as the major components. After the ‘chase’, the total 14C in host and mycelium declined but the proportions in starch or glycogen, protein, cell wall and nucleic acid fractions increased. Total 14C in haustorial complexes increased but that contained in sucrose and glycerol decreased and that in mannitol increased. During both ‘pulse’ and ‘chase’, the quantity of 14C in the haustorial complexes was small compared with that in the mycelial and leaf fractions. These results indicate that transport of host sugars to the fungus is mediated by haustoria. Sucrose and glycerol are either translocates or metabolic intermediates in this process and mannitol is the major primary sink of the fungus. Glycogen and other macromolecules are produced at a later stage in the fungus. Polysaccharides and lipids are important sinks at the host‐haustorial interface. These results are discussed in relation to the regulation of transport at the host‐parasite interface. Copyright © 1982, Wiley Blackwell. All rights reserved