EFFECT OF AUXINS AND ECTOMYCORRHIZAL ELICITORS ON WALL-BOUND PROTEINSAND ENZYMES OF SPRUCE [PICEA-ABIES (L) KARST] CELLS

Elicitors of the ectomycorrhizal fungus Hebeloma crustuliniforme and a uxins (IAA, NAA and 2,4-D) were tested for their effects on apoplastic proteins and enzymes of suspension cultured cells of Picea abies (L.) Karst. The ectomycorrhizal elicitor increased the amount of some ioni cally wall-bound proteins (36, 28, 24, 21 kDa) and decreased the amoun t of others (61, 22 kDa). The elicitor triggered an H2O2 burst and enh anced the peroxidase (EC 1.11.1.7) activity of the Picea cells by incr easing one of the two wall-bound peroxidase isoforms. Auxins significa ntly suppressed the elicitor induction of peroxidase but did not influ ence the elicitor-triggered H2O2 burst. The elicitors and auxin did no t change the amount and the pattern of wall-bound invertase isoforms ( EC 3.2.1.26) of spruce cells. However, auxin reduced the uptake of glu cose by spruce cells and increased the acidification of the cell cultu re medium. Since Hebeloma lacks apoplastic invertase as well as a sucr ose uptake system, utilization of plant-derived sucrose depends on the apoplastic plant invertase activity. Although the host invertase is c onstitutive, the fungus might be able to increase this invertase activ ity within a mycorrhiza by lowering the pH of the interface towards th e pH optimum of the enzyme via the action of auxin. This fungus-releas ed hormone could increase the H+ extrusion of plant cells by activatio n of the plant membrane H+-ATPases. Additionally, an auxin-dependent s uppression of glucose uptake by cortical root cells could improve the glucose supply for the fungus. Furthermore, the fungal auxin might sup press the elicitor induced formation of defense enzymes, such as perox idase.