Single-stranded oligodeoxynucleotides induce plant defence in Arabidopsis thaliana

Abstract

Background and Aims Single-stranded DNA oligodeoxynucleotides (ssODNs) have been shown to elicit immune responses in mammals. In plants, RNA and genomic DNA can activate immunity, although the exact mechanism through which they are sensed is not clear. The aim of this work was to study the possible effect of ssODNs on plant immunity. Key Results The ssODNs IMT504 and 2006 increased protection against the pathogens Pseudomonas syringae pv. tomato DC3000 and Botrytis cinerea but not against tobacco mosaic virus-Cg when infiltrated in Arabidopsis thaliana. In addition, ssODNs inhibited root growth and promoted stomatal closure in a concentration-dependent manner, with half-maximal effective concentrations between 0.79 and 2.06 µm. Promotion of stomatal closure by ssODNs was reduced by DNase I treatment. It was also diminished by the NADPH oxidase inhibitor diphenyleneiodonium and by coronatine, a bacterial toxin that inhibits NADPH oxidase-dependent reactive oxygen species (ROS) synthesis in guard cells. In addition it was found that ssODN-mediated stomatal closure was impaired in bak1-5, bak1-5/bkk1, mpk3 and npr1-3 mutants. ssODNs also induced early expression of MPK3, WRKY33, PROPEP1 and FRK1 genes involved in plant defence, an effect that was reduced in bak1-5 and bak1-5/bkk1 mutants. Conclusions ssODNs are capable of inducing protection against pathogens through the activation of defence genes and promotion of stomatal closure through a mechanism similar to that of other elicitors of plant immunity, which involves the BAK1 co-receptor, and ROS synthesis.

Extracellular self-RNA: A danger elicitor in pepper induces immunity against bacterial and viral pathogens in the field

“…Compared with the autotoxicity induced in plants by self-eDNA application previously ( Barbero et al, 2016 ; Duran-Flores and Heil, 2018 ; Serrano-Jamaica et al, 2020 ; Toum et al, 2020 ), it is noteworthy that self-eRNA-induced plant immunity was not accompanied by any growth penalty (also referred to as the allocation fitness cost; Figure 3 ). We cannot explain why allocation fitness cost is not required in the field trial of self-eRNA, but we have two hypotheses.…”

“…Like DAMP signaling in animals, infiltration of Arabidopsis thaliana seedling leaves with single-stranded oligodeoxynucleotides (ssODNs) elicited defense response against Pseudomonas syringae pv. tomato ( Pto ) and Botrytis cinerea but not against Tobacco mosaic virus and inhibited growth via the BAK co-receptor and ROS generation ( Toum et al, 2020 ). Besides plant self-eDNAs, a mixture of fragmented 100 μg/ml non-self-eDNAs derived from plant pathogenic fungi including Phytophthora capsici, Fusarium oxysporum, and Rhizoctonia solani reduced the mortality of pepper ( Capsicum annuum L.) plants by up to 40% ( Serrano-Jamaica et al, 2020 ).…”

XAP5 CIRCADIAN TIMEKEEPER Affects Both DNA Damage Responses and Immune Signaling in Arabidopsis

“…However, the appearance of the DNA damage marker γ-H2A.X as soon as 2 h after pathogen infection (much earlier than the first observable signs of plant cell death; Zhang et al, 2004;Song et al, 2015) suggest DNA damage may not just be an indirect product of the plant hypersensitive response. Indeed, damaged DNA (both foreign and host) has been reported to potentiate immune responses (Wen et al, 2009;Yakushiji et al, 2009;Gallucci and Maffei, 2017;Toum et al, 2020). Finally, the ability of DNA damaging treatments to promote innate immunity (Kunz et al, 2008;Yan et al, 2013) also suggests DNA damage and its consequent response pathways may activate immune signaling in plants.…”

ATM and ATR, two central players of the DNA damage response, are involved in the induction of systemic acquired resistance by extracellular DNA, but not the plant wound response

“…To determine importance of CpG motifs ( 23 ), the ODNs IMT504 (5’-CATCATTTTGTCATTTTGTCATT-3’) and 2006 (5’- TCGTCGTTTTGTCGTTTTGT-3’) and their complementary sequences (IMT504c: 5’- AATGACAAAATGACAAAATGATG-3’; 2006c: 5’-ACAAAACGACAAAACGACGA-3’) were purchased from Sigma Aldrich and used as single stranded DNA (ssDNA). To generate double stranded DNA (dsDNA), each ODN was annealed with its complementary sequence in a C1000 Thermal cycler (Biorad) by heating to 95°C for 3 minutes and cooling to room temperature.…”

“…Treatments with plant DNA, genomic or plasmid bacterial DNA, or synthetic single stranded oligodeoxynucleotides (ssODNs), were shown to trigger early immune responses that are highly conserved between plants and mammals, including Ca 2+ fluxes, membrane depolarization, the formation of reactive oxygen species (ROS) such as hydrogen peroxide (H 2 O 2 ), or the activation of mitogen-activated protein kinases (MAPKs) ( 9 , 20 – 22 , 25 , 27 , 34 , 35 ). The responses include massive transcriptomic reprogramming ( 24 , 25 , 35 ), and studies at the phenotypic level reported not only increased immunity (‘resistance’) to microbial pathogens, but also increased ‘defence’ to plant-specific pests such as leaf and sap-sucking herbivores ( 21 , 23 , 26 , 27 , 29 , 33 – 36 ). Strikingly, stronger responses to self- in comparison to nonself-DNA were reported in most, although not all, of the studies that compared DNA from different sources.…”