Bacteria-zinc co-localisation implicates enhanced synthesis of cysteine-rich peptides in zinc detoxification when Brassica juncea is inoculated with Rhizobium leguminosarum

Gbotemi A. Adediran, Bryne Ngwenya, J. Frederick W. Mosselmans, Kate Heal

Research output: Contribution to journalArticlepeer-review

Abstract

• Some plant growth promoting bacteria (PGPB) are enigmatic in enhancing plant growth in the face of increased metal accumulation in plants. Since most PGPB colonise plant root epidermis, we hypothesised that PGPB confer tolerance to metals through changes in speciation at the root epidermis.
• We employed a novel combination of fluorophore-based confocal laser scanning microscopic imaging and synchrotron based microscopic X-ray fluorescence mapping with X-ray Absorption Spectroscopy to characterise bacterial localisation, Zn distribution and speciation in the roots of Brassica juncea grown in Zn contaminated media (400 mg kg-1 Zn) with the endophytic Pseudomonas brassicacearum, and rhizospheric Rhizobium leguminosarum.
• PGPB enhanced epidermal Zn sequestration relative to PGBP-free controls while the extent of endophytic accumulation depended on the colonisation mode of each PGBP. Increased root accumulation of Zn and increased tolerance to Zn was associated predominantly with R. leguminosarum and was likely due to the co-ordination of Zn with cysteine-rich peptides in the root endodermis, suggesting enhanced synthesis of phytochelatins or glutathione.
• Our mechanistic model of enhanced Zn accumulation and detoxification in plants inoculated with R. leguminosarum has particular relevance to PGPB enhanced phytoremediation of soils contaminated through mining and oxidation of sulfur-bearing Zn minerals or engineered nanomaterials such as ZnS.
Original languageEnglish
Pages (from-to)280-293
Number of pages14
JournalNew Phytologist
Volume209
Issue number1
Early online date26 Nov 2015
DOIs
Publication statusPublished - Jan 2016

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