A new proteinaceous pathogen‐associated molecular pattern (PAMP) identified in Ascomycete fungi induces cell death in Solanaceae

Abstract

Pathogen-associated molecular patterns (PAMPs) are detected by plant pattern recognition receptors (PRRs), which gives rise to PAMP-triggered immunity (PTI). We characterized a novel fungal PAMP, Cell Death Inducing 1 (RcCDI1), identified in the Rhynchosporium commune transcriptome sampled at an early stage of barley (Hordeum vulgare) infection. The ability of RcCDI1 and its homologues from different fungal species to induce cell death in Nicotiana benthamiana was tested following agroinfiltration or infiltration of recombinant proteins produced by Pichia pastoris. Virus-induced gene silencing (VIGS) and transient expression of Phytophthora infestans effectors PiAVR3a and PexRD2 were used to assess the involvement of known components of PTI in N. benthamiana responses to RcCDI1. RcCDI1 was highly upregulated early during barley colonization with R. commune. RcCDI1 and its homologues from different fungal species, including Zymoseptoria tritici, Magnaporthe oryzae and Neurospora crassa, exhibited PAMP activity, inducing cell death in Solanaceae but not in other families of dicots or monocots. RcCDI1-triggered cell death was shown to require N. benthamiana Brassinosteroid insensitive 1-Associated Kinase 1 (NbBAK1), N. benthamiana suppressor of BIR1-1 (NbSOBIR1) and N. benthamiana SGT1 (NbSGT1), but was not suppressed by PiAVR3a or PexRD2. We report the identification of a novel Ascomycete PAMP, RcCDI1, recognized by Solanaceae but not by monocots, which activates cell death through a pathway that is distinct from that triggered by the oomycete PAMP INF1.

Leucine-rich repeat receptor-like gene screen reveals that Nicotiana RXEG1 regulates glycoside hydrolase 12 MAMP detection

“…Based on current knowledge, BAK1 and SOBIR1 participate solely in signaling mediated by LRR receptors, but not receptors with other types of ectodomains such as LysM-receptors or lectin receptor kinases 53 , 54 . Recently, multiple novel MAMPs were identified that require BAK1 or both BAK1 and SOBIR1 45 , 55 , indicating that the corresponding receptors may belong to the LRR class. Moreover, the recognition of certain MAMPs is restricted in Solanaceous plants 29 , 55 .…”

“…Recently, multiple novel MAMPs were identified that require BAK1 or both BAK1 and SOBIR1 45 , 55 , indicating that the corresponding receptors may belong to the LRR class. Moreover, the recognition of certain MAMPs is restricted in Solanaceous plants 29 , 55 . Therefore, the silencing of the LRR receptor candidates should be a straightforward approach to identify recognition receptors for each MAMP, which will ultimately lead to improved plant resistance.…”

Foxtail mosaic virus: A Viral Vector for Protein Expression in Cereals

“…This limits the experimental throughput. Furthermore, avoiding this first step of virus inoculum buildup in N. benthamiana may be necessary when testing constructs for the expression of generic cell death-inducing proteins (Lacomme and Santa Cruz, 1999;Tang et al, 2015;Kettles et al, 2018), predicted proteinaceous pathogen-associated molecular patterns (Franco-Orozco et al, 2017), or certain candidate pathogen effector proteins that may be recognized by the corresponding immune receptors in this plant species (Dagvadorj et al, 2017;Kettles et al, 2017). Therefore, we assessed the possibility of delivering the FoMV VOX vector directly into wheat leaves using infiltration with the recAdeficient A. tumefaciens strain COR308 harboring the disarmed pTi derivative plasmid pMP90 and the helper plasmid pCH32, which provide extra copies of the virA and virG genes (Hamilton, 1997), and a corresponding protocol that was claimed to be efficient in delivering BSMV-derived gene-silencing constructs directly to wheat leaves (Panwar et al, 2013).…”

BcXYG1, a Secreted Xyloglucanase from Botrytis cinerea, Triggers Both Cell Death and Plant Immune Responses

“…NbBAK1 or NbSOBIR1 expression was silenced using VIGS, as described previously (Kettles et al, 2017). pTRV2-GFP was used as a control, and tobacco NbBAK1 and NbSOBIR1 expression levels were determined by qRT-PCR analysis as described previously (Franco-Orozco et al, 2017). Briefly, A. tumefaciens strain GV3101 harboring pTRV1, pTRV2-GFP, pTRV2-NbBAK1, or pTRV2-NbSOBIR1 constructs were cultured in Luria-Bertani medium containing 50 mg mL 21 kanamycin and incubated at 28°C for 24 h. Bacteria cells were harvested by centrifugation at 5,000g and washed twice in infiltration buffer (10 mM MgCl 2 and 10 mM MES, pH 5.6), and cell density was adjusted to OD 600 = 0.2.…”