Altered properties and structures of root exudate polysaccharides in a root hairless mutant of barley

Galloway, Andrew F and Akhtar, Jumana and Burak, Emma and Marcus, Susan E and Field, Katie J and Dodd, Ian C and Knox, Paul (2022) Altered properties and structures of root exudate polysaccharides in a root hairless mutant of barley. Plant Physiology. ISSN 0032-0889

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Abstract

Abstract Root exudates and rhizosheaths of attached soil are important features of growing roots. To 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. In contrast, the root exudate of 2-week old brb plants contained ∼25-fold more detectable xyloglucan epitope relative to WT. Root system immunoprints confirmed the higher levels of release of the xyloglucan epitope from brb root apices and root axes relative to WT. Epitope detection with anion-exchange chromatography indicated that the increased detection of xyloglucan in brb exudates was due to enhanced abundance of a neutral polymer. Conversely, brb root exudates contained decreased amounts of an acidic polymer, with soil-binding properties, containing the xyloglucan epitope and glycoprotein and heteroxylan epitopes relative to WT. We therefore propose that, in addition to physically structuring soil particles, root hairs facilitate rhizosheath formation by releasing a soil-binding polysaccharide complex.

Item Type:
Journal Article
Journal or Publication Title:
Plant Physiology
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/1300/1314
Subjects:
ID Code:
174207
Deposited By:
Deposited On:
08 Aug 2022 10:30
Refereed?:
Yes
Published?:
Published
Last Modified:
08 Aug 2022 10:30