Effect of salinity on the zinc(II) binding efficiency of siderophore functional groups and implications for salinity tolerance mechanisms in barley

George H R Northover,Dominik J Weiss,Ramon Vilar,Enrique Garcia-España,Salvador Blasco,Haris Ahmed,Yiru Mao

doi:10.1038/s41598-021-95736-7

Abstract

Bacteria, fungi and grasses use siderophores to access micronutrients. Hence, the metal binding efficiency of siderophores is directly related to ecosystem productivity. Salinization of natural solutions, linked to climate change induced sea level rise and changing precipitation patterns, is a serious ecological threat. In this study, we investigate the impact of salinization on the zinc(II) binding efficiency of the major siderophore functional groups, namely the catecholate (for bacterial siderophores), α-hydroxycarboxylate (for plant siderophores; phytosiderophores) and hydroxamate (for fungal siderophores) bidentate motifs. Our analysis suggests that the order of increasing susceptibility of siderophore classes to salinity in terms of their zinc(II) chelating ability is: hydroxamate < catecholate < α-hydroxycarboxylate. Based on this ordering, we predict that plant productivity is more sensitive to salinization than either bacterial or fungal productivity. Finally, we show that previously observed increases in phytosiderophore release by barley plants grown under salt stress in a medium without initial micronutrient deficiencies, are in line with the reduced zinc(II) binding efficiency of the α-hydroxycarboxylate ligand and hence important for the salinity tolerance of whole-plant zinc(II) status.

Highlights

Organic ligands play a critical role in the cycling of trace metals
One explanation for an increase in phytosiderophore release by grasses under salt stress is that it is a response to secondary micronutrient limitations induced by the disruption of uptake p athways[40]. This explanation leads to the hypothesis that previously observed increases in phytosiderophore release by barley plants grown under salt stress in a medium without initial micronutrient deficiencies, are important for the salinity tolerance of whole-plant zinc(II) status
We examine whether the susceptibility of the different classes of siderophore correlates with the hydrophobicity of the representative ligands. (iii) we test the hypothesis that previously observed increases in phytosiderophore release by barley plants grown under salt stress in a medium without initial micronutrient deficiencies, are important for the salinity tolerance of whole-plant zinc(II) status

Summary

Introduction

Organic ligands play a critical role in the cycling of trace metals. Through complexation processes, they control the mobility of contaminants and regulate the bioavailability of micronutrients[1,2,3]. Values of protonation constants for PYR, GLY and AHA (this study), and D FOB30, are reported at different [NaCl] and T = 298.1 K in Table 1 with the parameters of ionic strength dependence.

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Results

Conclusion