MYB72, a node of convergence in induced systemic resistance triggered by a fungal and a bacterial beneficial microbe

Abstract

Colonisation of plant roots by selected beneficial Trichoderma fungi or Pseudomonas bacteria can result in the activation of a systemic defence response that is effective against a broad spectrum of pathogens. In Arabidopsis thaliana, induced systemic resistance (ISR) triggered by the rhizobacterial strain Pseudomonas fluorescens WCS417r is regulated by a jasmonic acid‐ and ethylene‐dependent defence signalling pathway. Jasmonic acid and ethylene also play a role in Trichoderma‐induced resistance. To further investigate the similarities between rhizobacteria‐ and Trichoderma‐induced resistance, we studied the response of Arabidopsis to root colonisation by Trichoderma asperellum T34. In many aspects T34‐ISR was similar to WCS417r‐ISR. First, colonisation of the roots by T34 rendered the leaves more resistant to the bacterial pathogen Pseudomonas syringae pv. tomato, the biotrophic oomycete Hyaloperonospora parasitica and the necrotrophic fungus Plectosphaerella cucumerina. Second, treatment of the roots with T34 primed the leaf tissue for enhanced jasmonic acid‐responsive gene expression and increased formation of callose‐containing papillae upon pathogen attack. Third, T34‐ISR was fully expressed in the salicylic acid impaired mutant sid2, but blocked in the defence regulatory mutant npr1. Finally, we show that the root‐specific transcription factor MYB72, which is essential in early signalling steps of WCS417r‐ISR, is also required for T34‐ISR. Together, these results indicate that the defence pathways triggered by beneficial Trichoderma and Pseudomonas spp. strains are highly similar and that MYB72 functions as an early node of convergence in the signalling pathways that are induced by these different beneficial microorganisms.

MYB transcription factor genes as regulators for plant responses: an overview

“…The functions of MYB proteins have been investigated in numerous plant species such as Arabidopsis, maize, cotton, rice (Oryza sativa), petunia (Petunia hybrida), snapdragon (Antirrhinum majus), grapevine (Vitis vinifera L.), poplar (Populus tremuloides) and apple (Malus domestica), using both genetic and molecular analyses. In the past decade, the R2R3-MYB genes have been extensively studied and members of the MYB family have been found to be involved in a variety of biological functions like phenylpropanoid metabolism (Grotewold et al 1994;Hichri et al 2011), biotic and abiotic stress (Segarra et al 2009;Lippold et al 2009), cell shape such as Am MIXTA (Noda et al 1994), differentiation (Oppenheimer et al 1991;Kang et al 2009;Xie et al 2010), hormone responses i.e. AtMYB2 (Urao et al 1993), GAMYB and CpMYB (Gubler et al 1995 ;Iturriaga et al 1996), formation of B-type cyclin (Ito et al 2001) or during plant defense reactions i.e.…”

“…Raffaele et al (2008) proposed that AtMYB30 modulated hypersensitive response via very-long-chain fatty acids (VLCFAs) by themselves or VLCFA derivatives and thus playing a role in programmed cell death. Segarra et al (2009) and Van der Ent et al (2008) demonstrated that the defence pathways triggered by beneficial Trichoderma, Rhizobacteria and Pseudomonas spp. strains were highly similar and root-specific transcription factor MYB72 functioned as an early node of convergence in the signalling pathways that were induced by these different beneficial microorganisms playing role in defence response in Arabidopsis.…”

Impact of root exudates and plant defense signaling on bacterial communities in the rhizosphere. A review

“…have been achieved to prevent crop losses due to diseases (Cook 2000), it is estimated that plant diseases cause a 20% yield loss in food and cash crops worldwide (Schumann and D'Arcy 2006). Disease incidence can be minimized by agricultural practices such as crop rotation, the application of chemical pesticides and breeding of resistant crop varieties.…”

“…There are multiple mechanisms by which naturally occurring beneficial bacteria and fungi can suppress disease incidence or severity, including antibiosis, competition for nutrients and space, and the production of lyctic enzymes (Weller 1988;Chet et al 1990;Chet and Inbar 1994;Handelsman and Stabb 1996;Raaijmakers et al 2002;Haas and Defago 2005;Van Loon 2007). Of special interest is the enhancement of plant innate defense responses against pathogens by beneficial bacteria and fungi that occur naturally on plant roots (Zehnder et al 2001;Kloepper et al 2004;Hoitink et al 2006;Van Wees et al 2008;Segarra et al 2009). This induced resistance of plant defenses is effective against a wide variety of plant pathogens for prolonged periods.…”

Tomato leafminer [(Tuta absoluta Meyrick) (Lepidoptera: Gelechiidae)] and its current ecofriendly management strategies: A review

“…For instance, Trichoderma species is plant growth promoting fungus that is commercially available and widely used in agriculture that induces systemic resistance against microbial pathogens in plants (Harman et al, 2004;Trillas et al, 2009;Segarra et al, 2009). When the Trichoderma spp.…”