Arabidopsis thaliana PAD4 encodes a lipase-like gene that is important for salicylic acid signaling

Abstract

The Arabidopsis PAD4 gene previously was found to be required for expression of multiple defense responses including camalexin synthesis and PR-1 gene expression in response to infection by the bacterial pathogen Pseudomonas syringae pv. maculicola. This report describes the isolation of PAD4. The predicted PAD4 protein sequence displays similarity to triacyl glycerol lipases and other esterases. The PAD4 transcript was found to accumulate after P. syringae infection or treatment with salicylic acid (SA). PAD4 transcript levels were very low in infected pad4 mutants. Treatment with SA induced expression of PAD4 mRNA in pad4 -1, pad4 -3, and pad4 -4 plants but not in pad4 -2 plants. Induction of PAD4 expression by P. syringae was independent of the regulatory factor NPR1 but induction by SA was NPR1-dependent. Taken together with the previous observation that pad4 mutants have a defect in accumulation of SA upon pathogen infection, these results suggest that PAD4 participates in a positive regulatory loop that increases SA levels, thereby activating SA-dependent defense responses.

Constitutive salicylic acid‐dependent signaling in cpr1 and cpr6 mutants requires PAD4

“…The mutations in pad4-1 and dnd1-1 may be null, as they cause translation stops at aa 359 of a 542 aa protein, and aa 290 of a 720 aa protein, respectively Jirage et al, 1999). For determination of phenotypes, plants were grown in Metromix 2000 soil (Scotts-Sierra Horticultural Products, Marysville, OH, USA) in a controlled-environment chamber (22°C, 80% RH, 100 mmol m ±2 sec ±1¯u orescent illumination, 12 h light/12 h dark cycle).…”

Categories of Resistance to Greenbug (Homoptera: Aphididae) Biotype I in <B> <I>Aegilops tauschii</I> </B> Germplasm

“…In addition, EPG analysis indicated that PAD4 controls insect feeding from sieve elements (Pegadaraju et al, 2007). PAD4 is also involved in plant defense against a subset of pathogens, where it modulates the synthesis of SA and the phytoalexin, camalexin (Glazebrook et al, 1997;Zhou et al, 1998;Jirage et al, 1999). However, genetic studies have suggested that the involvement of PAD4 in plant defense against GPA is not due to its involvement in SA and camalexin metabolism .…”

“…However, genetic studies have suggested that the involvement of PAD4 in plant defense against GPA is not due to its involvement in SA and camalexin metabolism . The N-terminal half of PAD4 shares homology with α/β-fold acyl hydrolases that include lipases and esterases (Zhou et al, 1998;Jirage et al, 1999).…”

Not to be suppressed? Rethinking the host response at a root-parasite interface

“…By having this comparison available, it is possible to suggest that the observed host response to root-knot nematodes was likely subject to some form of suppression even though the genes studied showed differential expression. The PAD4 gene of Arabidopsis, which is induced as part of the defense response to microbial pathogen infection, is another example that was confirmed to be involved in salicylate signaling by comparing its attenuated response in signaling mutants to that of wild-type plants treated directly in parallel [56]. The correct inference of host defense signaling responses can therefore only be achieved when these signals are placed in the appropriate context and contrasted to control treatments of a tissue or cell type that has relevance to the specific interaction being studied.…”