Broad-Spectrum Acquired Resistance in Barley Induced by thePseudomonasPathosystem Shares Transcriptional Components withArabidopsisSystemic Acquired Resistance

Abstract

Inducible resistance responses play a central role in the defense of plants against pathogen attack. Acquired resistance (AR) is induced alongside defense toward primary attack, providing broad-spectrum protection against subsequent pathogen challenge. The localization and molecular basis of AR in cereals is poorly understood, in contrast with the well-characterized systemic acquired resistance (SAR) response in Arabidopsis. Here, we use Pseudomonas syringae as a biological inducer of AR in barley, providing a clear frame of reference to the Arabidopsis-P. syringae pathosystem. Inoculation of barley leaf tissue with the nonadapted P. syringae pv. tomato avrRpm1 (PstavrRpm1) induced an active local defense response. Furthermore, inoculation of barley with PstavrRpm1 resulted in the induction of broad-spectrum AR at a distance from the local lesion, "adjacent" AR, effective against compatible isolates of P. syringae and Magnaporthe oryzae. Global transcriptional profiling of this adjacent AR revealed similarities with the transcriptional profile of SAR in Arabidopsis, as well as transcripts previously associated with chemically induced AR in cereals, suggesting that AR in barley and SAR in Arabidopsis may be mediated by analogous pathways.

Contribution of the drought tolerance‐related Stress‐responsive NAC1 transcription factor to resistance of barley to Ramularia leaf spot

“…Constitutive levels of HvSNAC1 and ROS scavenger gene transcripts were assessed in each of the two transgenic lines compared with GP using qRT‐PCR. RNA was extracted from 14‐day‐old prophyll leaves, processed and converted to cDNA (Colebrook et al ., ). Transcripts were amplified with gene‐specific primers (http://onlinelibrary.wiley.com/doi/10.1111/mpp.12173/suppinfo, see Supporting Information; Shagimardanova et al ., ) and the Sybr Green JumpStart™ Taq Ready mix system (Sigma‐Aldrich, St. Louis, MO, USA), as described previously (Colebrook et al ., ).…”

“…RNA was extracted from 14-day-old prophyll leaves, processed and converted to cDNA (Colebrook et al, 2012). Transcripts were amplified with gene-specific primers (Table S1, see Supporting Information; Shagimardanova et al, 2010) and the Sybr Green JumpStart™ Taq Ready mix system (Sigma-Aldrich, St. Louis, MO, USA), as described previously (Colebrook et al, 2012). cDNA samples were normalised with geNorm (Vandesompele et al, 2002) using five reference genes (elongation factor 1α, glyceraldehyde 3-phosphate dehydrogenase, cyclophilin, ubiquitin, α-tubulin; Burton et al, 2004;McGrann et al, 2009;Rostoks et al, 2003).…”

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

“…Irrespective of the importance of SA, signals contained in petiole (phloem) exudates from SAR signalemitting Arabidopsis leaves effectively protect wheat from head blight caused by Fusarium graminearum (Chaturvedi et al, 2008). Furthermore, transcriptional changes associated with a LAR-like immune response in distal parts of barley leaves adjacent to sites inoculated with Pseudomonas syringae pv tomato carrying the effector locus AvrRpm1 revealed commonalities with Arabidopsis SAR (Colebrook et al, 2012). Taken together, signaling associated with induced resistance, including a role of SA, appears relatively conserved between dicots and monocots.…”

Host and Nonhost Response to Attack by Fungal Pathogens

“…These observations rather argue against an important role of M. oryzae toxins and support the notion that the fungus maintains a "quasibiotrophic" interaction until late during the infection process, which might be characterized by nutrient uptake from living cells while tolerating surrounding host cell death and maybe also recycling of nutrients leaking out from decayed host tissue. In line with the proposed "quasi-biotrophic" lifestyle of M. oryzae on barley, it was observed that a primary inoculation with the bacterial pathogen Pseudomonas syringae resulted in acquired resistance to subsequent fungal attack, which was characterized by transcriptional changes resembling salicylic acid-mediated systemic acquired resistance (SAR) against biotrophs in Arabidopsis as well as chemically induced resistance against powdery mildew in barley and wheat (Colebrook et al 2012).…”