Dynamic Chemical Communication between Plants and Bacteria t

发布日期：2020-01-18 14:49 来源：网络作者：网络浏览次数：

Mohamed A. Farag,
Huiming Zhang &
Choong-Min Ryu

Journal of Chemical Ecology volume 39, pages1007–1018(2013)

Abstract

Certain plant growth-promoting rhizobacteria (PGPR) elicit induced systemic resistance (ISR) and plant growth promotion in the absence of physical contact with plants viavolatile organic compound (VOC) emissions. In this article, we review the recent progess made by research into the interactions between PGPR VOCs and plants, focusing on VOC emission by PGPR strains in plants. Particular attention is given to the mechanisms by which these bacterial VOCs elicit ISR. We provide an overview of recent progress in the elucidation of PGPR VOC interactions from studies utilizing transcriptome, metabolome, and proteome analyses. By monitoring defense gene expression patterns, performing 2-dimensional electrophoresis, and studying defense signaling null mutants, salicylic acid and ethylene have been found to be key players in plant signaling pathways involved in the ISR response. Bacterial VOCs also confer induced systemic tolerance to abiotic stresses, such as drought and heavy metals. A review of current analytical approaches for PGPR volatile profiling is also provided with needed future developments emphasized. To assess potential utilization of PGPR VOCs for crop plants, volatile suspensions have been applied to pepper and cucumber roots and found to be effective at protecting plants against plant pathogens and insect pests in the field. Taken together, these studies provide further insight into the biological and ecological potential of PGPR VOCs for enhancing plant self-immunity and/or adaptation to biotic and abiotic stresses in modern agriculture.

Keywords

PGPR ISR IST Volatile organic compounds Headspace

Abbreviations

PGPR
Plant growth-promoting rhizobacteria
ISR
Induced systemic resistance
IST
Induced systemic tolerance
VOC
Volatile organic compound

I-plate system used for assessing plant growth promotion in response to plant growth-promoting rhizobacteria (PGPR) volatiles exposure. This setup allows only volatile compounds to be exchanged, while preventing any diffusion of non-volatile metabolites through the medium.

Model of induced systemic resistance (ISR) and induced systemic tolerance (IST) mechanisms elicited by volatile organic compounds (VOCs) emitted from plant growth-promoting rhizobacteria. ISR and IST elicited by plant growth-promoting rhizobacteria (PGPR) against biotic and abiotic stresses respectively underground (root) and aboveground (shoot). Broken arrows indicate plant responses through individual regulatory component in plants; solid arrows indicate plant compounds affected by bacterial VOCs. Some PGPR strains, indicated in yellowish rods on the plant roots, produce VOCs such as 2,3-butanediol, which results in upregulated pathogenesis-related (PR) genes via salicylic acid and ethylene signalling pathways conferring ISR against phytopathogens and herbivores. Bacterial VOCs downregulate HKT1 expression in roots but upregulate it in shoot tissues, orchestrating lower Na+ levels and recirculation of Na+ and upregulate FIT1 in the whole plant under high salt, metal toxicity, and drought conditions. Abbreviations: FIT1, Fedeficiency- induced transcription factor 1; HKT1, high-affinity K+ transporter 1; ISR, induced systemic resistance; IST, induced systemic tolerance; PGPR, plant-growth-promoting rhizobacteria.

Proposed scheme for volatile analysis procedure from plant growth-promoting rhizobacteria (PGPR) showing the following steps: I) volatile collection using either a dynamic headspace sampling by blowing humidified air over PGPR cultures and venting through adsorbent filters, or b static solid phase microextraction (SPME) using fibers, later desorbed inside GC, followed by II) volatile analysis using GC/MS and peaks deconvolution using AMDIS software, allowing for the resolution of complex volatile blend components, III) multivariate data analysis i.e., principal component analysis (PCA) to help reveal differences and similarities between PGPR strains.