Manipulation of rhizosphere organisms to enhance glomalin production and C sequestration: Pitfalls and promises

Abstract

rhizosphere organisms to enhance glomalin production and C-sequestration: Pitfalls and promises. Can. J. Plant Sci. 94: 1025Á1032. Arbuscular mycorrhizal fungi (AMF) reportedly produce glomalin, a glycoprotein that has the potential to increase soil carbon (C) and nitrogen (N) storage. We hypothesized that interactions between rhizosphere microorganisms, such as plant growth-promoting rhizobacteria (PGPR), and AMF, would influence glomalin production. Our objectives were to determine the effects of AMF/PGPR interactions on plant growth and glomalin production in the rhizosphere of pea (Pisum sativum L.) with the goal of enhancing C and N storage in the rhizosphere. One component of the study focussed on the molecular characterization of glomalin and glomalin-related soil protein (GRSP) using complementary synchrotronbased N and C X-ray absorption near-edge structure (XANES) spectroscopy, pyrolysis field ionization mass spectrometry (Py-FIMS), and proteomics techniques to characterize specific organic C and N fractions associated with glomalin production. Our research ultimately led us to conclude that the proteinaceous material extracted, and characterized in the literature, as GRSP is not exclusively of AMF origin. Our research supports the established concept that GRSP is important to soil quality, and C and N storage, irrespective of origin. However, efforts to manipulate this important soil C pool will remain compromised until we more clearly elucidate the chemical nature and origin of this resource. . Manipulation des organismes de la rhizosphe`re en vue d'accroıˆtre la synthe`se de glomaline et la se´questration du C : e´cueils et promesses. Can. J. Plant Sci. 94: 1025Á1032. Les mycorhizes a`arbuscules (MA), dit-on, produisent de la glomaline, glycoprote´ine susceptible d'augmenter le stockage du carbone (C) et de l'azote (N) dans le sol. Les auteurs sont partis de l'hypothe`se que les interactions des microorganismes de la rhizosphe`re comme les rhizobacte´ries qui acce´le`rent la croissance des plantes (RACP) et les MA pourraient agir sur la synthe`se de la glomaline. Leur but e´tait de pre´ciser les conse´quences des interactions MA/RACP sur la croissance des plantes et sur la production de glomaline dans la rhizosphe`re du pois (Pisum sativum L.) en vue de rehausser le stockage du C et du N dans la rhizosphe`re. Une partie de l'e´tude devait permettre la caracte´risation mole´culaire de la glomaline et des prote´ines du sol qui y sont apparente´es (PSAG). Les auteurs ont recouru a`des techniques comple´mentaires comme la spectroscopie de structure pre`s du front d'absorption des rayons X (XANES) du N et du C assiste´e par synchrotron, la spectrome´trie de masse par ionisation de champ avec pyrolyse (Py-FIMS) et la prote´omique pour caracte´riser les fractions spe´cifiques de C et de N associe´es a`la synthe`se de la glomaline. Ces recherches les ont amene´s a`conclure que le mate´riel prote´ine´extrait et de´crit dans la litte´rature comme e´tant des PSAG importe pour la qualite´du sol ainsi que pour le...

Effect of Salinity Stress and Microbial Inoculations on Glomalin Production and Plant Growth Parameters of Snap Bean (Phaseolus vulgaris)

“…However, uncertainty remains as the AMF may have previously been present in our soil and contributed GRSP contents, but a general increasing trend of GRSP release over time indicates the effect of our induced inoculation treatments. Similar observations were reported by Walley et al [74] when they studied the effect of AM and plant growth-promoting rhizobacteria on glomalin production in un-sterilized soil. For EEG, the salinity showed no or little effect on natural glomalin present in the soil.…”

PGPR Mediated Alterations in Root Traits: Way Toward Sustainable Crop Production

“…Cell walls of hyphal Arbuscular mycorrhizal fungi (AMF) produce glomalin and, death of hyphae deposited in the soil, further incorporated into soil organic matter (SOM) pool. Interaction of AMF and PGPR improved the glomalin production in rhizosphere of pea (Pisum sativum L.) and further enhanced C and N storage in rhizosphere (Walley et al, 2014). In boreal forest ecosystems root-associated fungi acts as organic decomposers and belowground mediators for C transport and respiration (Clemmensen et al, 2013).…”

Apatite Stimulates the Deposition of Glomalin-Related Soil Protein in a Lowbush Blueberry Commercial Field

“…About 60 g of sterilized and sieved sand was poured into 8 × 12 cm nylon bags (SEFAR NITEX, Filmar, Montreal, Quebec, QC, Canada) having 50 µm pores (Figure 1). This pore size was selected because it (1) minimizes sand contamination (inputs) and losses (outputs) during incubation and (2) allows soil microorganisms (fungal hyphae and bacteria) to colonize the sand bag [39], as GSRP is likely produced by those soil microorganisms [19]. Waterproof glue (LePage®), Mississauga, Ontario, Canada) was used to seal the bags (Figure 1).…”

“…However, several lines of evidence have brought a more nuanced definition and questions regarding even the glycoprotein nature of glomalin. For instance, glomalin was found to be co-extracted with humic substances [16][17][18] and, therefore, has a spectral signature more related to humic materials than to carbohydrates [19]. Based on this, Rillig [20] suggested that part of this operational pool of glomalin [termed as glomalin-related soil proteins (GRSP) and simply defined as any substance extracted by autoclaving soil in a citrate buffer and quantified using a colorimetric protein assay] may also come from general fungal hydrophobins (i.e., not necessarily of AM origin).…”

“…Following the idea that glomalin may originate from numerous paths and organisms, GRSP deposition may occur in infertile and wind-sensitive wild blueberry fields that are largely dominated by ericaceous shrubs (Vaccinium and Kalmia can comprise about 95% of the vegetation of sand dunes), which are not AM plants (although there are sparse records of AM colonization in ericaceous hosts in the literature [22][23][24][25]). Given the well-recognized importance of GRSP to soil fertility, irrespective of its origin [19], this operational pool could represent a useful biochemical indicator of soil fertility and quality [26][27][28]. Therefore, the challenge may not necessarily be to identify mechanistically the origin of GRSP, but rather to identify the drivers of its production.…”