Cereal root exudates contain highly structurally complex polysaccharides with soil‐binding properties

Andrew F. Galloway; Jumana Akhtar; Susan E. Marcus; Nathan Fletcher; Katie Field; Paul Knox

doi:10.1111/tpj.14852

A soil-binding polysaccharide complex released from root hairs functions in rhizosheath formation

10.1101/2021.04.15.440065 ◽

2021 ◽

Author(s):

Andrew F. Galloway ◽

Jumana Akhtar ◽

Emma Burak ◽

Susan E. Marcus ◽

Katie J. Field ◽

...

Keyword(s):

Root Exudates ◽

Root Exudate ◽

Binding Capacity ◽

Root Hairs ◽

Arabinogalactan Protein ◽

Wild Type ◽

Binding Properties ◽

Polysaccharide Complex ◽

Acidic Form ◽

Neutral Polymer

SUMMARYTo elucidate factors involved in rhizosheath formation, wild type (WT) barley (Hordeum vulgare L. cv. Pallas) and a root hairless mutant, bald root barley (brb), were investigated with a combination of physiological, biochemical and immunochemical assays. When grown in soil, WT barley roots bound ∼5-fold more soil than brb per unit root length. High molecular weight (HMW) polysaccharide exudates of brb roots had less soil-binding capacity than those of WT root exudates. Carbohydrate and glycan monoclonal antibody analyses of HMW polysaccharide exudates indicated differing glycan profiles. Relative to WT plants, root exudates of brb had reduced signals for arabinogalactan-protein (AGP), extensin and heteroxylan epitopes than brb. In contrast, the brb root exudate contained ∼25-fold more detectable xyloglucan epitope relative to WT. Epitope detection chromatography indicated that the increased detection of xyloglucan in brb exudates was due to enhanced abundance of a neutral polymer. Exudate preparations from brb had decreased amounts of an acidic form of xyloglucan associated with root-hair located glycoprotein and heteroxylan epitopes and with soil-binding properties. Therefore, in addition to physically structuring soil particles, root hairs facilitate rhizosheath formation by releasing a soil-binding polysaccharide complex.One sentence summaryThe root exudate of a root hairless mutant of barley, relative to wild type, has an altered pattern of polysaccharide epitopes and lesser amounts of an acidic soil-binding polysaccharide complex.

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Determination of allelochemicals in spring cereal cultivars of different competitiveness

Weed Science ◽

10.1017/s0043174500092171 ◽

1999 ◽

Vol 47 (5) ◽

pp. 498-504 ◽

Cited By ~ 51

Author(s):

Ali Baghestani ◽

Claudel Lemieux ◽

Gilles D. Leroux ◽

Regis Baziramakenga ◽

Regis R. Simard

Keyword(s):

Root Exudates ◽

High Performance ◽

Hypocotyl Growth ◽

Allelopathic Potential ◽

Weed Interference ◽

Weed Growth ◽

Negative Effect ◽

Brassica Kaber ◽

Cereal Cultivars ◽

Cereal Root

Competitive cereal cultivars are less susceptible than others to weed interference. Their characterization may provide selection criteria that can be used as guidelines to develop new, even more competitive cultivars. Root exudates are a potential means by which competitive cultivars reduce weed growth. The objectives of this study were to evaluate the effect of cereal root exudates onBrassica kaber(DC.) L. C. Wheeler growth, to isolate and characterize the allelochemical compounds released by spring cereal cultivars, and to determine if a relation exists between these allelochemicals and cultivar competitiveness. Highly competitive (HC) and lesser competitive (LC) cultivars of four crop kinds (Triticum aestivumL. [wheat],Avena sativaL. [wild oat], two- and six-rowedHordeum vulgareL. [barley]) were selected based on previous work. Exudates from undisturbed root systems ofB. kaberand cereals were collected and used in a bioassay test withB. kaber.Root exudates were analyzed for 16 common phenolic compounds using high-performance liquid chromatography (HPLC). Bioassays indicated that cereal exudates had no negative effect onB. kabergermination, but all concentrations of cereal root exudates inhibitedB. kaberroot and hypocotyl growth. As cereal root exudate concentration increased,B. kabergrowth decreased. For each crop kind,B. kabergrowth inhibition was greater with HC cultivars than with LC cultivars. The root exudates of all crop kinds and cultivars contained benzoic, caffeic, ferulic,o-coumaric, and vanillic acids as well as scopoletin. Para-hydroxybenzoic acid was found in exudates fromT. aestivum, A. sativa, and two-rowedH. vulgarecultivars. Para-coumaric acid was not identified in root exudates from LCH. vulgarecultivars. Gentisic acid was produced byA. sativaandH. vulgare.Vanillic ando-coumaric acids along with scopoletin may be responsible for the allelopathic effects ofH. vulgare, T. aestivum, andA. sativacultivars. These three compounds may be useful as possible indicators of allelopathic potential of genotypes under development and thus considered for use in breeding programs.

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A new family of fluorescent calcium indicators designed to resist leakage or for measuring calcium near membranes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100168578 ◽

1994 ◽

Vol 52 ◽

pp. 168-169

Author(s):

Martin Poenie ◽

Akwasi Minta ◽

Charles Vorndran

Keyword(s):

Metal Binding ◽

Acetoxymethyl Ester ◽

Binding Properties ◽

Fura 2 ◽

New Family ◽

Anion Transporter ◽

Calcium Indicator ◽

Calcium Indicators ◽

High Calcium ◽

Intracellular Compartmentalization

The use of fura-2 as an intracellular calcium indicator is complicated by problems of rapid dye leakage and intracellular compartmentalization which is due to a probenecid sensitive anion transporter. In addition there is increasing evidence for localized microdomains of high calcium signals which may not be faithfully reported by fura-2.We have developed a new family of fura-2 analogs aimed at addressing some of these problems. These new indicators are based on a modified bapta which can be readily derivatized to produce fura-2 analogs with a variety of new properties. The modifications do not affect the chromophore and have little impact on the spectral and metal binding properties of the indicator. One of these new derivatives known as FPE3 is a zwitterionic analog of fura-2 that can be loaded into cells as an acetoxymethyl ester and whose retention in cells is much improved. The improved retention of FPE3 is important for both cuvettebased measurements of cell suspensions and for calcium imaging.

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