Long distance movement of DIR1 and investigation of the role of DIR1-like during systemic acquired resistance in Arabidopsis

Abstract

DIR1 is a lipid transfer protein (LTP) postulated to complex with and/or chaperone a signal(s) to distant leaves during Systemic Acquired Resistance (SAR) in Arabidopsis. DIR1 was detected in phloem sap-enriched petiole exudates collected from wild-type leaves induced for SAR, suggesting that DIR1 gains access to the phloem for movement from the induced leaf. Occasionally the defective in induced resistance1 (dir1-1) mutant displayed a partially SAR-competent phenotype and a DIR1-sized band in protein gel blots was detected in dir1-1 exudates suggesting that a highly similar protein, DIR1-like (At5g48490), may contribute to SAR. Recombinant protein studies demonstrated that DIR1 polyclonal antibodies recognize DIR1 and DIR1-like. Homology modeling of DIR1-like using the DIR1-phospholipid crystal structure as template, provides clues as to why the dir1-1 mutant is rarely SAR-competent. The contribution of DIR1 and DIR1-like during SAR was examined using an Agrobacterium-mediated transient expression-SAR assay and an estrogen-inducible DIR1-EGFP/dir1-1 line. We provide evidence that upon SAR induction, DIR1 moves down the leaf petiole to distant leaves. Our data also suggests that DIR1-like displays a reduced capacity to move to distant leaves during SAR and this may explain why dir1-1 is occasionally SAR-competent.

Arabidopsis AZI1 family proteins mediate signal mobilization for systemic defence priming

“…1e), as previously reported 12,34,35 . AZI1:GFP was present in the microsomal and chloroplast fractions, but was not detected in soluble and apoplastic fractions (Fig.…”

“…no. 632459, 1:3,000), HA antibody (Covance 16B12, 1:1,750), H þ ATPase antibody (Agrisera AS07260, 1:7,500), cytosolic FBP antibody (Agrisera AS04 043, 1:3,000), BiP antibody (SPA-818, Stressgen, 1:3,000), ATPase b antibody 68 (1:3,000), DIR1 antibody 11,35 (1:20,000) and PR1 antibody 69 (1:3,000). For analysis of AZI1/EARLI1 native proteins from Arabidopsis an anti-EARLI1 polyclonal antibody 37 (that also recognizes AZI1) was used (1:750).…”

N-Acyl-Homoserine Lactone Primes Plants for Cell Wall Reinforcement and Induces Resistance to Bacterial Pathogens via the Salicylic Acid/Oxylipin Pathway

“…Methyl salicylate (MeSA), dehydroabietinal, azelaic acid, a glycerol-3-phosphatederived factor, pipecolic acid, as well as the putative lipid transfer proteins DIR1 and DIR1-like are proposed to be involved in the induction of systemic resistance (Park et al, 2007;Jung et al, 2009;Chanda et al, 2011;Chaturvedi et al, 2012;Návarová et al, 2012;Champigny et al, 2013). The current model predicts that all signal cascades induced by these molecules require NPR1 (Dempsey and Klessig, 2012;Shah and Zeier, 2013).…”

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

“…These signals include the methylated derivative of SA methyl salicylate (Park et al, 2007), glycerol-3-phosphate (Chanda et al, 2011), the diterpenoid dehydroabietinal (Chaturvedi et al, 2012), the C 9 dicarboxylic acid azelaic acid (Jung et al, 2009), and the lipid transfer proteins DEFECTIVE IN INDUCED RESISTANCE1 (DIR1; Maldonado et al, 2002), DIR1-like (Champigny et al, 2013), and AZELAIC ACID INDUCED1 (AZI1; Jung et al, 2009). Glycerol-3-phosphate might be part of a positive feedback loop, with DIR1 and AZI1 acting downstream of azelaic acid (Yu et al, 2013;Gao et al, 2014;Shah et al, 2014), which accumulates by autooxidation of C18 unsaturated fatty acids, possibly downstream of nitric oxide and reactive oxygen species, to promote SAR (Zoeller et al, 2012;Wang et al, 2014;Wittek et al, 2014).…”