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Article|01 Apr 2021|OPEN
Tissue-specific signatures of metabolites and proteins in asparagus roots and exudates
Stefanie Döll1,2, Roxana Djalali Farahani-Kofoet3, Rita Zrenner3, Andrea Henze4 & Katja Witzel 3,
1Leibniz Institute of Plant Biochemistry, Weinberg 3, 06120 Halle/Saale, Germany
2Present address: German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103 Leipzig, Germany
3Leibniz Institute of Vegetable and Ornamental Crops, TheodorEchtermeyer-Weg 1, 14979 Großbeeren, Germany
4University of Potsdam, Institute of Nutritional Science, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany

Horticulture Research 8,
Article number: 86 (2021)
doi: 10.1038/hortres.2021.86
Views: 223

Received: 01 Oct 2020
Revised: 22 Jan 2021
Accepted: 01 Mar 2021
Published online: 01 Apr 2021

Abstract

Comprehensive untargeted and targeted analysis of root exudate composition has advanced our understanding of rhizosphere processes. However, little is known about exudate spatial distribution and regulation. We studied the specific metabolite signatures of asparagus root exudates, root outer (epidermis and exodermis), and root inner tissues (cortex and vasculature). The greatest differences were found between exudates and root tissues. In total, 263 non-redundant metabolites were identified as significantly differentially abundant between the three root fractions, with the majority being enriched in the root exudate and/or outer tissue and annotated as ‘lipids and lipid-like molecules’ or ‘phenylpropanoids and polyketides’. Spatial distribution was verified for three selected compounds using MALDI-TOF mass spectrometry imaging. Tissue-specific proteome analysis related root tissue-specific metabolite distributions and rhizodeposition with underlying biosynthetic pathways and transport mechanisms. The proteomes of root outer and inner tissues were spatially very distinct, in agreement with the fundamental differences between their functions and structures. According to KEGG pathway analysis, the outer tissue proteome was characterized by a high abundance of proteins related to ‘lipid metabolism’, ‘biosynthesis of other secondary metabolites’ and ‘transport and catabolism’, reflecting its main functions of providing a hydrophobic barrier, secreting secondary metabolites, and mediating water and nutrient uptake. Proteins more abundant in the inner tissue related to ‘transcription’, ‘translation’ and ‘folding, sorting and degradation’, in accord with the high activity of cortical and vasculature cell layers in growth- and development-related processes. In summary, asparagus root fractions accumulate specific metabolites. This expands our knowledge of tissue-specific plant cell function.