TY - JOUR

T1 - Do plants use root-derived proteases to promote the uptake of soil organic nitrogen?

AU - Greenfield, Lucy M.

AU - Hill, Paul W.

AU - Paterson, Eric

AU - Baggs, Elizabeth M.

AU - Jones, Davey L.

PY - 2020/11

Y1 - 2020/11

N2 - AimsThe capacity of plant roots to directly acquire organic nitrogen (N) in the form of oligopeptides and amino acids from soil is well established. However, plants have poor access to protein, the central reservoir of soil organic N. Our question is: do plants actively secrete proteases to enhance the breakdown of soil protein or are they functionally reliant on soil microorganisms to undertake this role?MethodsGrowing maize and wheat under sterile hydroponic conditions with and without inorganic N, we measured protease activity on the root surface (root-bound proteases) or exogenously in the solution (free proteases). We compared root protease activities to the rhizosphere microbial community to estimate the ecological significance of root-derived proteases.ResultsWe found little evidence for the secretion of free proteases, with almost all protease activity associated with the root surface. Root protease activity was not stimulated under N deficiency. Our findings suggest that cereal roots contribute one-fifth of rhizosphere protease activity.ConclusionsOur results indicate that plant N uptake is only functionally significant when soil protein is in direct contact with root surfaces. The lack of protease upregulation under N deficiency suggests that root protease activity is unrelated to enhanced soil N capture.

AB - AimsThe capacity of plant roots to directly acquire organic nitrogen (N) in the form of oligopeptides and amino acids from soil is well established. However, plants have poor access to protein, the central reservoir of soil organic N. Our question is: do plants actively secrete proteases to enhance the breakdown of soil protein or are they functionally reliant on soil microorganisms to undertake this role?MethodsGrowing maize and wheat under sterile hydroponic conditions with and without inorganic N, we measured protease activity on the root surface (root-bound proteases) or exogenously in the solution (free proteases). We compared root protease activities to the rhizosphere microbial community to estimate the ecological significance of root-derived proteases.ResultsWe found little evidence for the secretion of free proteases, with almost all protease activity associated with the root surface. Root protease activity was not stimulated under N deficiency. Our findings suggest that cereal roots contribute one-fifth of rhizosphere protease activity.ConclusionsOur results indicate that plant N uptake is only functionally significant when soil protein is in direct contact with root surfaces. The lack of protease upregulation under N deficiency suggests that root protease activity is unrelated to enhanced soil N capture.

KW - Aminopeptidase

KW - Peptidase

KW - Plant nutrition

KW - Proteinase

KW - Root exudation

U2 - 10.1007/s11104-020-04719-6

DO - 10.1007/s11104-020-04719-6

M3 - Article

VL - 456

SP - 355

EP - 367

JO - Plant and Soil

JF - Plant and Soil

SN - 0032-079X

IS - 1-2

ER -