A pH signaling mechanism involved in the spatial distribution of calcium and anion fluxes in ectomycorrhizal roots

Abstract

Summary Mycorrhization is a typical example of a host–pathogen symbiotic interaction where the pathogen cell biology and the host immune response coevolved several functional links. Here, the role played by ion fluxes across the root concerning nutrient uptake, osmoregulation, growth and signaling events is addressed. An ion‐selective vibrating probe system was used to determine the net fluxes of protons (H+), calcium (Ca2+) and anions (A−) along nonmycorrhizal and ectomycorrhizal (ECM) roots of Eucalyptus globulus colonized by Pisolithus sp. These data show that, from five root zones analyzed, the main effect of fungal colonization was localized to the elongation zone. Here, strong changes in ion dynamics and rhizosphere acidification capacity were observed. Additionally, ion fluxes exhibited periodic fluctuations. To verify whether these fluctuations corresponded to sustained oscillations, continuous wavelet time spectrum analysis was applied and it was determined that H+ and A− fluxes from ECM roots had longer periods than nonmycorrhizal roots. By contrast, Ca2+ oscillations were completely abolished following fungal interaction. These results are interpreted in the light of a working model in which nutrient uptake and stimulation of growth are mediated by ECM fungi and may be pH‐dependent. Furthermore, the variations detected in ECM roots for H+ and A− fluxes suggest a main contribution from the plant, while the results obtained for Ca2+ point to a significant involvement of the fungus.

Paxillus involutus Strains MAJ and NAU Mediate K+/Na+ Homeostasis in Ectomycorrhizal Populus × canescens under Sodium Chloride Stress

“…6). Our data agree with the findings of Ramos et al (2009), who reported significant H + efflux from Eucalyptus globulus roots (the apex, meristematic, and elongation zones) colonized with Pisolithus species. The mycorrhiza-stimulated H + efflux is due to the activity of plasma membrane H + -ATPase in the EM associations.…”

“…3 canescens roots exhibit increased Ca 2+ enrichment during mycorrhizal symbiosis with P. involutus strain MAJ (Langenfeld-Heyser et al, 2007). Ramos et al (2009) found that EM roots are more efficient than non-EM roots in taking up Ca 2+ from the external medium. Under NaCl stress, Ca 2+ regulates K + /Na + homeostasis in a salt-overly-sensitive3 mutant and wildtype Arabidopsis (Arabidopsis thaliana; Liu and Zhu, 1997).…”

“…Under NaCl stress, Ca 2+ regulates K + /Na + homeostasis in a salt-overly-sensitive3 mutant and wildtype Arabidopsis (Arabidopsis thaliana; Liu and Zhu, 1997). Ca 2+ has been suggested to restrict Na + uptake via voltage-independent-NSCCs Tester and Davenport, 2003) and to restrain K + loss through DA-KORCs and DA-NSCCs (Shabala et al, 2006a;Sun et al, 2009b;Chen and Polle, 2010 , and H + fluxes were found on root surfaces, with increased fluxes after colonization of different hosts with either ectomycorrhizae or arbuscular mycorrhizae (Ramos et al, 2008(Ramos et al, , 2009 Scanning electron microscopy-energy dispersive x-ray spectrometry (SEM-EDX) was used to measure relative changes in the Na + , K + , and Ca 2+ concentrations in the cross-sections of roots and leaves. NaCl treatment (50 mM) for 1 week significantly increased Na + in the roots and leaves, with the exception of plants colonized with P. involutus strain NAU (Fig.…”

Ecophysiology of iron homeostasis in plants

“…These enzymes are considered eletrogenic pumps, because they transport positive charge in the form of H + , generating a difference in charges on either side of the membrane, called membrane potential (MP), and simultaneously generate a difference in the chemical potential of H + or proton concentration gradient (ΔpH) (Yan et al 2002;Ramos et al 2009a). The electrochemical difference produced by this enzyme is used as a driving force in fundamental cellular processes, such as activation of secondary transporters, cellular signaling, nutrient uptake and proton extrusion (Palmgren 2001).…”

Determining the fluxes of ions (Pb2+, Cu2+ and Cd2+) at the root surface of wetland plants using the scanning ion-selective electrode technique

“…In general, it is currently possible to use the SIET or MIFE system to measure net fluxes of ions (such as H + , Ca 2+ , K + , Na + , Cl − , Mg 2+ , NH 4 + , NO 3 − , Cd 2+ ) as well as gaseous molecules (such as O 2 and NO) and other compounds (indoleacetic acid, IAA) in real time in various biological systems (Pineros et al 1998;McLamore et al 2009;Wu et al 2010;Ramos et al 2009;Mancuso et al 2005;Mancuso et al 2000). To our knowledge, only a Cd 2+ liquid-membrane ion selective microelectrode (ISME) was routinely applied in the root system (Pineros et al 1998;Farrell et al 2005;Li et al 2012), although several other heavy metal ions (e.g.…”