Mycorrhiza formation on Norway spruce (Picea abies) roots affects the pathway of anaplerotic CO2 fixation

Abstract

R. 1996. Myeorrhiza formation on Norway spruce (Picea abies) roots affects the pathway of anaplerotic CO, Activities of carboxylaEion enzymes were analyzed in the mycelium of the mycorrhizal fungus Amanita muscaria (L. ex Fr.) Hooker, in non-myeorrhizal short roots of Norway spruce (Picea abies IL.] Karsl.) and in mycorrhizas of these two partnens. While pyruvate carboxylase (PC, EC 6.4.1.1) and phosphoenolpyruvate carboxykinase activities (PEPCK, EC 4.1.1.49) could be detected in the mycelium of A. muscaria, phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) was only active in root tissue. In .4. muscaria, PC activity was generally low (around 10 nmol mg" protein min"') but PEPCK activity was above 250 nmol mg"' protein min . Mycorrhizal development on short roots decreased PEPC activity by more than 15%, although dilution by the funeal biomass in mycorrhizas was only 35%. This reduction in activity was paralleled by a decreased content of PEPC protein. By means of micro-analytical methods it was shown that PEPC activity was lowest in the central zones of the mycon-Mzas, whereas PEPC activity was highest in the corresponding central sections in non-mycorrhizal shon roots. '^c'Oj labelling, on Ihe other hand, revealed that in vivo CO, fixation was higher in mycontiizas compared to non-mycorrhizal short roots. It is concluded that fungal cai'boxylases (probably PEPCK) are important for anaplerotic CO; fixation during nitrogen assimilation in mycorrhizas of Noi-way spmce.Physiol. Plam. %. 19%

Isotopic evidence of biotrophy and unusual nitrogen nutrition in soil‐dwelling Hygrophoraceae

“…Hobbie et al . () found that fresh conifer needles were unexpectedly enriched in 14 C, dating to 0–3 years prior to collection, and they discussed the various factors that could account for both this and the similar dating of 14 C in basidiocarps of known mycorrhizal species, including anaplerotic fixation of CO 2 (Wingler et al ., ), internal recycling of C within mycelial systems and uptake of C from soil amino acids by fungi. However, Treseder et al .…”

“…Fungal colonization of senescent or recently dead roots cannot be excluded, since this would also have a recent 14 C signature. Hobbie et al (2002) found that fresh conifer needles were unexpectedly enriched in 14 C, dating to 0-3 years prior to collection, and they discussed the various factors that could account for both this and the similar dating of 14 C in basidiocarps of known mycorrhizal species, including anaplerotic fixation of CO 2 (Wingler et al, 1996), internal recycling of C within mycelial systems and uptake of C from soil amino acids by fungi. However, Treseder et al (2006) found no evidence of transfer of 14 C from labelled litter to ECM fungi.…”

Recent advances in exploring physiology and biodiversity of ectomycorrhizas highlight the functioning of these symbioses in ecosystems

“…In plants, phosphoenolpyruvate carboxylase (PEPC) is an important anaplerotic enzyme. Under regular ammonium supply, mycorrhiza formation causes a signi¢cant decrease of both PEPC activity and PEPC protein (Western blot) of roots of spruce seedlings in comparison to the non-mycorrhizal condition [125]. A microhistochemical analysis showed that this e¡ect was most pronounced in the area of most intense interaction of both partners.…”

“…A microhistochemical analysis showed that this e¡ect was most pronounced in the area of most intense interaction of both partners. In parallel, the rates of carboxylation of whole mycorrhizas were signi¢cantly increased, implying that under conditions of symbiosis, ammonium assimilation and thus anaplerotic carboxylation is shifted from the root to the fungus [125]. This is presumably the basis for the transfer of amino acids such as glutamine, glutamate or asparagine from the fungus to the host [17].…”

Axenic mycorrhization of wild type and transgenic hybrid aspen expressing T-DNA indoleacetic acid-biosynthetic genes

“…The axenic synthesis of ectomycorrhiza is an important requisite for the investigation of symbiotic interaction on a biochemical or molecular level (Guttenberger and Hampp 1992;Martin and Tagu 1995). From such approaches we now get some idea about plant/fungus metabolic interaction with regard to carbohydrate and nitrogen metabolism (Botton and Chalot 1995;Hampp and Schaeffer 1995;Wingler et al 1996), and molecular regulation (Martin and Tagu 1995).…”