Signaling Pathways That Regulate the Enhanced Disease Resistance of Arabidopsis “Defense, No Death” Mutants

Abstract

Arabidopsis dnd1 and dnd2 mutants lack cyclic nucleotide-gated ion channel proteins and carry out avr/R-mediated defense with a greatly reduced hypersensitive response (HR). They also exhibit elevated broad-spectrum disease resistance and constitutively elevated salicylic acid (SA) levels. We examined the contributions of NPR1, SID2 (EDS16), NDR1 and EIN2 to dnd phenotypes. Mutations that affect SA accumulation or signaling (sid2, npr1 and ndr1) abolished the enhanced resistance of dnd mutants against Pseudomonas syringae pv. tomato and Hyaloperonospora parasitica but not Botrytis cinerea. When SA-associated pathways were disrupted, the constitutive activation of NPR1-dependent and NPR1-independent/SA-dependent pathways was redirected toward PDF1.2-associated pathways. This PDF1.2 over-expression was down-regulated after infection by P. syringae. Disruption of ethylene signaling abolished the enhanced resistance to B. cinerea but not P. syringae or H. parasitica. However, loss of NPR1, SID2, NDR1 or EIN2 did not detectably alter the reduced HR in dnd mutants. The susceptibility of dnd ein2 plants to B. cinerea despite their reduced-HR phenotype suggests that cell death repression is not the primary cause of dnd resistance to necrotrophic pathogens. The partial restoration of resistance to B. cinerea in dnd1 npr1 ein2 triple mutants indicated that this resistance is not entirely EIN2-dependent. The above findings indicate that the broad spectrum resistance of dnd mutants occurs due to activation and/or sensitization of multiple defense pathways, yet none of the investigated pathways are required for the reduced-HR phenotype.

Broad-Spectrum Suppression of Innate Immunity Is Required for Colonization of Arabidopsis Roots by the FungusPiriformospora indica

“…Thus, SA-mediated defense against the fungus is NPR1 independent (Fig. 6), as has been reported for dnd1, cpr1, cpr5, cpr6, and cpr30, which exert a constitutive SA defense (Clarke et al, 2000;Genger et al, 2008;Gou et al, 2009). In contrast, camalexin and JA, which are generally involved in Figure 9.…”

Ca 2 + signaling by plant Arabidopsis thaliana Pep peptides depends on AtPepR1, a receptor with guanylyl cyclase activity, and cGMP-activated Ca 2+ channels

“…RT-PCR was performed on progeny of the atpepr1 cross to confirm that the transfer-DNA insertion was homozygous and prevented accumulation of full-length transcripts. Homozygous dnd1 plants expressing aequorin were identified using derived cleaved amplified polymorphic sequence analysis and an MboI restriction site (42). Seeds of Arabidopsis plants expressing the reporter protein GUS under control of the PDF1.2 promoter (PDF1.2::GUS) were obtained from the Arabidopsis Biological Resource Center (stock no.…”

Transcriptomics of induced defense responses to greenbug aphid feeding in near isogenic wheat lines

“…Cysteine-rich Receptor Kinases (CRKs) belonging to DUF26 class proteins are known to mediate biotic and abiotic stress responses by activating ABA, SA, and JA hormone signaling [52,53]. Six transcripts related to Domain of Unknown Function 26 (DUF26) RLKs were also altered in a comparison between RB and SB after greenbug infestation (Fig.…”