Lipid transfer proteins and protease inhibitors as key factors in the priming of barley responses to Fusarium head blight disease by a biocontrol strain of Pseudomonas fluorescens

Abstract

Strains of non-pathogenic pseudomonad bacteria, can elicit host defence responses against pathogenic microorganisms. Pseudomonas fluorescens strain MKB158 can protect cereals from pathogenesis by Fusarium fungi, including Fusarium head blight which is an economically important disease due to its association with both yield loss and mycotoxin contamination of grain. Using the 22 K barley Affymetrix chip, trancriptome studies were undertaken to determine the local effect of P. fluorescens strain MKB158 on the transcriptome of barley head tissue, and to discriminate transcripts primed by the bacterium to respond to challenge by Fusarium culmorum, a causal agent of the economically important Fusarium head blight disease of cereals. The bacterium significantly affected the accumulation of 1203 transcripts and primed 74 to positively, and 14 to negatively, respond to the pathogen (P = 0.05). This is the first study to give insights into bacterium priming in the Triticeae tribe of grasses and associated transcripts were classified into 13 functional classes, associated with diverse functions, including detoxification, cell wall biosynthesis and the amplification of host defence responses. In silico analysis of Arabidopsis homologs of bacterium-primed barley genes indicated that, as is the case in dicots, jasmonic acid plays a role in pseudomonad priming of host responses. Additionally, the transcriptome studies described herein also reveal new insights into bacterium-mediated priming of host defences against necrotrophs, including the positive effects on grain filling, lignin deposition, oxidative stress responses, and the inhibition of protease inhibitors and proteins that play a key role in programmed cell death.

Bacteria-Triggered Systemic Immunity in Barley Is Associated with WRKY and ETHYLENE RESPONSIVE FACTORs But Not with Salicylic Acid

“…Such a mechanism of primed induced resistance is not unprecedented in barley. Local application of P. fluorescens primes barley head tissue for 88 gene expression changes upon a Fusarium culmorum challenge infection of the treated tissue (Petti et al, 2010). Moreover, systemic leaves of plants pretreated with the root-colonizing and plant growth-promoting fungus Piriformospora indica display enhanced resistance to Bgh (Waller et al, 2005).…”

Auxin as a player in the biocontrol of Fusarium head blight disease of barley and its potential as a disease control agent

“…P. fluorescens strain MKB158 had the ability to induce local and systemic responses in wheat and barley tissue, resulting in enhanced resistance to Fusarium seedling blight and head blight (FSB and FHB) disease [14-17]. The objective of this study was to determine what hormones are involved in the defence responses to FHB in barley that are primed by the bacterium P. fluorescens strain MKB158.…”

“…The objective of this study was to determine what hormones are involved in the defence responses to FHB in barley that are primed by the bacterium P. fluorescens strain MKB158. Based on in silico analysis of the upstream regions of genes involved in the primed response [17] we chose to determine whether the hormones ABA and IAA play a role in the biocontrol of FHB disease by P. fluorescens . Based on the assessment of both hormone levels and their effect on both the regulation of plant genes activated by the biocontrol bacterium and the development of FHB disease symptoms, we draw conclusions regarding the contribution of IAA and ABA to the local defence responses of barley plants primed by P. fluorescens .…”

Plant lipid transfer proteins: Evolution, expression and function

“…Some nsLTPs are however specifically expressed in one or a few tissues, including root, anther, trichomes or seed (Blilou et al, 2000;Choi et al, 2012;Kovalchuk et al, 2012). In many cases the expression of the nsLTPs are upregulated by different biotic and abiotic stresses, including abscisic acid and salicylic acid in strawberry and bacterial infection in barley (Yubero-Serrano et al, 2003;Petti et al, 2010). This have been shown for several additional nsLTPs from different species, including mungbean, bromegrass, sunflower, rice and Arabidopsis (Vignols et al, 1997;Liu and Lin, 2003;Wu et al, 2004;Gonorazky et al, 2005;Brotman et al, 2012).…”