An illuminated respiratory activity monitoring system identifies priming-active compounds in plant seedlings

Judith Loogen,André Müller,Roxanne Krug,Sophie Weber,Uwe Conrath,Arne Balzer,Jochen Büchs,Kathrin Schmitz,Ulrich Schaffrath,Jörg Pietruszk

doi:10.1186/s12870-021-03100-8

Abstract

BackgroundGrowing large crop monocultures and heavily using pesticides enhances the evolution of pesticide-insensitive pests and pathogens. To reduce pesticide use in crop cultivation, the application of priming-active compounds (PrimACs) is a welcome alternative. PrimACs strengthen the plant immune system and could thus help to protect plants with lower amounts of pesticides. PrimACs can be identified, for example, by their capacity to enhance the respiratory activity of parsley cells in culture as determined by the oxygen transfer rate (OTR) using the respiration activity monitoring system (RAMOS) or its miniaturized version, µRAMOS. The latter was designed for with suspensions of bacteria and yeast cells in microtiter plates (MTPs). So far, RAMOS or µRAMOS have not been applied to adult plants or seedlings, which would overcome the limitation of (µ)RAMOS to plant suspension cell cultures.ResultsIn this work, we introduce a modified µRAMOS for analysis of plant seedlings. The novel device allows illuminating the seedlings and records the respiratory activity in each well of a 48-well MTP. To validate the suitability of the setup for identifying novel PrimAC in Arabidopsis thaliana, seedlings were grown in MTP for seven days and treated with the known PrimAC salicylic acid (SA; positive control) and the PrimAC candidate methyl 1-(3,4-dihydroxyphenyl)-2-oxocyclopentane-1-carboxylate (Tyr020). Twenty-eight h after treatment, the seedlings were elicited with flg22, a 22-amino acid peptide of bacterial flagellin. Upon elicitation, the respiratory activity was monitored. The evaluation of the OTR course reveals Tyr020 as a likely PrimAC. The priming-inducing activity of Tyr020 was confirmed using molecular biological analyses in A. thaliana seedlings.ConclusionWe disclose the suitability of µRAMOS for identifying PrimACs in plant seedlings. The difference in OTR during a night period between primed and unprimed plants was distinguishable after elicitation with flg22. Thus, it has been shown that the µRAMOS device can be used for a reliable screening for PrimACs in plant seedlings.

Highlights

Growing large crop monocultures and heavily using pesticides enhances the evolution of pesticideinsensitive pests and pathogens
We present the setup for a light-emitting diode (LED)-μRAMOS combination and a standard procedure for the identification of new priming-active compounds (PrimACs) on plant seedlings
The plant seedlings are grown in each well of a 48-well microtiter plates (MTPs) in controlled light condition

Summary

Introduction

Growing large crop monocultures and heavily using pesticides enhances the evolution of pesticideinsensitive pests and pathogens. PrimACs can be identified, for example, by their capacity to enhance the respiratory activity of parsley cells in culture as determined by the oxygen transfer rate (OTR) using the respiration activity monitoring system (RAMOS) or its miniaturized version, μRAMOS. The latter was designed for with suspensions of bacteria and yeast cells in microtiter plates (MTPs). As the world population continuously grows, there is an increased need for food, feed, fibers, and bioenergy [29] These stocks are mainly derived from crops, such as corn, rice or wheat, that are usually grown in large monocultures. To avoid the risks that comes with synthetic pesticides, exploiting the plant immune system emerged as a supportive, or even alternative, approach for eco-friendly plant protection [8]

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