Bacterial Compound N,N-Dimethylhexadecylamine Modulates Expression of Iron Deficiency and Defense Response Genes in Medicago truncatula Independently of the Jasmonic Acid Pathway

Vicente Montejano-Ramírez,Eduardo Valencia-Cantero,Ernesto García-Pineda

doi:10.3390/plants9050624

Vicente Montejano-Ramírez, Eduardo Valencia-Cantero + Show 1 more

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https://doi.org/10.3390/plants9050624

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Abstract

Plants face a variety of biotic and abiotic stresses including attack by microbial phytopathogens and nutrient deficiencies. Some bacterial volatile organic compounds (VOCs) activate defense and iron-deficiency responses in plants. To establish a relationship between defense and iron deficiency through VOCs, we identified key genes in the defense and iron-deprivation responses of the legume model Medicago truncatula and evaluated the effect of the rhizobacterial VOC N,N-dimethylhexadecylamine (DMHDA) on the gene expression in these pathways by RT-qPCR. DMHDA increased M. truncatula growth 1.5-fold under both iron-sufficient and iron-deficient conditions compared with untreated plants, whereas salicylic acid and jasmonic acid decreased growth. Iron-deficiency induced iron uptake and defense gene expression. Moreover, the effect was greater in combination with DMHDA. Salicylic acid, Pseudomonas syringae, jasmonic acid, and Botrytis cinerea had inhibitory effects on growth and iron response gene expression but activated defense genes. Taken together, our results showed that the VOC DMHDA activates defense and iron-deprivation pathways while inducing a growth promoting effect unlike conventional phytohormones, highlighting that DMHDA does not mimic jasmonic acid but induces an alternative pathway. This is a novel aspect in the complex interactions between biotic and abiotic stresses.

Highlights

Plants are sessile organisms that interact with biotic and abiotic factors
These elicitors include flagellin, lipopolysaccharides, peptidoglycan, elongation factors, and siderophores, which are present in beneficial microorganisms and pathogens [2]; molecular patterns associated with herbivores, which include saliva and regurgitants of herbivorous insects [3]; and molecular patterns associated with damage, which include DNA, extracellular ATP, systemin, and oligogalacturonides produced in response to damage in plant cells [4]
Response to iron-deficiency stress has been linked to the defensive activation of both systemic acquired resistance (SAR) and induced systemic resistance (ISR) pathways [23]

Summary

Introduction

Plants are sessile organisms that interact with biotic and abiotic factors Biotic factors include both beneficial microorganisms, such as plant growth promoting rhizobacteria (PGPR) and phytopathogens, and herbivorous insects. Through the presence of membrane proteins known as pattern recognition receptors, plants can recognize diverse elicitors, such as molecular patterns associated with microbes. These elicitors include flagellin, lipopolysaccharides, peptidoglycan, elongation factors, and siderophores, which are present in beneficial microorganisms and pathogens [2]; molecular patterns associated with herbivores, which include saliva and regurgitants of herbivorous insects [3]; and molecular patterns associated with damage, which include DNA, extracellular ATP, systemin, and oligogalacturonides produced in response to damage in plant cells [4]

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