MYB72 Is Required in Early Signaling Steps of Rhizobacteria-Induced Systemic Resistance in Arabidopsis  

Abstract

Colonization of Arabidopsis thaliana roots by nonpathogenic Pseudomonas fluorescens WCS417r bacteria triggers a jasmonate/ ethylene-dependent induced systemic resistance (ISR) that is effective against a broad range of pathogens. Microarray analysis revealed that the R2R3-MYB-like transcription factor gene MYB72 is specifically activated in the roots upon colonization by WCS417r. Here, we show that T-DNA knockout mutants myb72-1 and myb72-2 are incapable of mounting ISR against the pathogens Pseudomonas syringae pv tomato, Hyaloperonospora parasitica, Alternaria brassicicola, and Botrytis cinerea, indicating that MYB72 is essential to establish broad-spectrum ISR. Overexpression of MYB72 did not result in enhanced resistance against any of the pathogens tested, demonstrating that MYB72 is not sufficient for the expression of ISR. Yeast two-hybrid analysis revealed that MYB72 physically interacts in vitro with the ETHYLENE INSENSITIVE3 (EIN3)-LIKE3 transcription factor EIL3, linking MYB72 function to the ethylene response pathway. However, WCS417r activated MYB72 in ISR-deficient, ethyleneinsensitive ein2-1 plants. Moreover, exogenous application of the ethylene precursor 1-aminocyclopropane-1-carboxylate induced wild-type levels of resistance in myb72-1, suggesting that MYB72 acts upstream of ethylene in the ISR pathway. Collectively, this study identified the transcriptional regulator MYB72 as a novel ISR signaling component that is required in the roots during early signaling steps of rhizobacteria-mediated ISR.

Plant immune responses triggered by beneficial microbes

“…Hence, MYB72 was assumed to act in concert with another signaling component. MYB72 interacted with the EIN3-like TF EIL3 in vitro, making EIL3 a potential candidate in this respect [43 ]. The interaction with EIL3 links MYB72 function to the ET response pathway involved in ISR, which was previously demonstrated to orchestrate ISR in the roots ( [44]; Figure 1).…”

“…Attack by pathogens or insects, as depicted on the right side of the figure, activates defense responses in the plant (yellow arrows), which is accelerated in ISR-primed plants (combined blue and yellow arrows (Figure 1). Both priming phenomena were abolished in the ISR mutants myb72 and npr1 [43 ], demonstrating the key role of priming in ISR. Some beneficial rhizobacteria, such as Paenibacillus alvei K165 prime for enhanced SA-dependent defenses [37], while others, such as selected endophytic actinobacteria, are able to prime both the SA and the JA/ET pathway [38 ].…”

“…Transcriptome analysis of Arabidopsis expressing WCS417-ISR revealed a set of 94 genes that were differentially expressed locally in the roots [39]. Knockout mutant analysis of a subset of these WCS417-responsive genes showed that the transcription factor (TF) MYB72 is required in early signaling steps of ISR [43 ]. Arabidopsis myb72 mutants were incapable of mounting ISR against both SA-controlled and JA-controlled pathogens, indicating that MYB72 is essential to establish broad-spectrum ISR.…”

Functional analysis of non-ribosomal peptide synthetases (NRPSs) in Trichoderma virens reveals a polyketide synthase (PKS)/NRPS hybrid enzyme involved in the induced systemic resistance response in maize

“…In contrast, root colonization by Trichoderma per se induces both priming effects and transcriptomic/metabolic changes in plants, including the triggering of defence response genes encoding enzymes such as phenylalanine ammonia lyase (pal), hydroperoxide lyase (hpl) and allene oxide synthase (aos) (Shoresh & Harman, 2008;Djonović et al, 2007;Vargas et al, 2008;Viterbo et al, 2005;Shoresh et al, 2010;Mastouri et al, 2010). PGPR and Trichoderma-mediated ISR, is different from pathogentriggered systemic acquired resistance (SAR), but both ISR and SAR require NPR1 (non-expressor of pathogenesisrelated genes; Van der Ent et al, 2008). ISR is mediated by jasmonate (JA) and ethylene (ET) response pathways whereas SAR is dependent on and mediated by salicylate (SA) signalling.…”

COMPORTAMIENTO AGRONÓMICO Y COMPOSICIÓN QUÍMICA DE TRES VARIEDADES DE Brachiaria EN DIFERENTES EDADES DE COSECHA

“…Los estudios realizados por Van der Ent et al (2008), llegaron a demostrar la inactivación de la RSI por P. fluoresccens WCS417r, al trabajar con plantas mutantes de A. thaliana al (knockout del T-DNA de los genes myb72-1 y myb72-2), siendo incapaces de mantener la RSI a patógenos: Pseudomonas syringae, Hyaloperonospora parasítica, Alternaria brassicicola y Botrytis cinérea. Además, la sobre-expresión del gen MYB72 no mejora la resistencia hacia los patógenos.…”