Disease relevance of PDF1.2

• Ectopic overproduction of GhHb1 in Arabidopsis led to constitutive expression of the defense genes PR-1 and PDF1.2, and conferred enhanced disease resistance to Pseudomonas syringae and tolerance to V. dahliae [1].
• No transcripts for pathogenesis-related PR-1, PR-5, or the pathogen-inducible plant defensin Pdf1.2 could be detected in uninoculated transgenic seedlings, indicating that all of the observed effects of the overexpressing lines are most likely the result of the toxicity of the THI2.1 thionin [2].

High impact information on PDF1.2

• Activation of the PDF1.2 and b-CHI, ethylene/JA-responsive genes, is, however, increased in these mutants [3].
• By contrast, ssi2 plants are compromised in the induction of the jasmonic acid (JA)-responsive gene PDF1.2 and in resistance to the necrotrophic pathogen Botrytis cinerea [4].
• Arabidopsis plants unable to accumulate SA produced 25-fold higher levels of JA and showed enhanced expression of the JA-responsive genes LOX2, PDF1.2, and VSP in response to infection by Pseudomonas syringae pv tomato DC3000, indicating that in wild-type plants, pathogen-induced SA accumulation is associated with the suppression of JA signaling [5].
• Exogenous application of salicylic acid to Arabidopsis-Pti4 plants suppressed the increased expression of PDF1.2 but further stimulated PR1 expression [6].
• Furthermore, exogenous application of BTH restored PDF1.2 expression in these plants [7].

Biological context of PDF1.2

• Whereas the NADPH oxidase mutants were affected in UV-B-dependent CHS, PYROA and MEB5.2 gene expression, the mkp1 mutant was affected in the general expression pattern of the pathogenesis-related (PR) and PDF1.2 genes [8].
• The observed up-regulation of the PDF1.2 gene in mutants defective in the SA-dependent signaling pathway points to a cross-talk between SA- and jasmonate/ethylene-dependent signaling pathways during pathogen ingress [9].
• Using stably transformed plants, we first characterized the extended promoter region that positively regulates basal expression from the PDF1.2 promoter [10].
• By analyzing the progeny of crosses between cpr22 plants and either NahG transgenic plants or npr1 mutants, all of the cpr22-associated phenotypes except PDF1.2 expression were found to be SA dependent [11].
• While the induction of the AtEBP transgene and PDF1.2 had similar DEX concentration requirements, the kinetics of induction differed significantly, with the AtEBP transgene being induced within 1 h and PDF1.2 only being induced between 24 and 48 h [12].

Associations of PDF1.2 with chemical compounds

• Here, we report the isolation and characterization of a 23-aa peptide from Arabidopsis, called AtPep1, which activates transcription of the defensive gene defensin (PDF1.2) and activates the synthesis of H(2)O(2), both being components of the innate immune response [13].
• In the present study, we show that, in addition to SA, ethylene and JA signaling also are required for the ssi1-conferred constitutive expression of PDF1.2 and the NPR1-independent expression of PR-1 [14].
• In support of this idea, we observed a marked synergy between ethylene and methyl jasmonate for the induction of PDF1.2 in plants grown under sterile conditions [15].
• These suggested that there was a transient synergistic enhancement in the expression of genes associated with either JA (PDF1.2 [defensin] and Thi1.2 [thionin]) or SA (PR1 [PR1a-beta-glucuronidase in tobacco]) signaling when both signals were applied at low (typically 10-100 microm) concentrations [16].
• PDF1.2, a plant defensin gene, was strongly induced in all transgenic lines examined following treatment with DEX, including empty vector lines that did not show any observable DEX-induced growth defect [12].

Regulatory relationships of PDF1.2

• Here we show that mutations of the Arabidopsis WRKY33 gene encoding a WRKY transcription factor cause enhanced susceptibility to the necrotrophic fungal pathogens Botrytis cinerea and Alternaria brassicicola concomitant with reduced expression of the jasmonate-regulated plant defensin PDF1.2 gene [17].
• Activation of the plant defensin gene PDF1.2 in Arabidopsis by pathogens has been shown previously to be blocked in the ethylene response mutant ein2-1 and the jasmonate response mutant coi1-1 [15].

Other interactions of PDF1.2

• Ectopic CAPIP2 expression in Arabidopsis was accompanied by the expression of Arabidopsis PR-1 and PDF1.2 genes [18].
• However, the cpr5 npr1 plants retained heightened resistance to P. parasitica Noco2 and elevated expression of the defensin gene PDF1.2, implying that NPR1-independent resistance signaling also occurs [19].
• A large number of well-known JA responsive genes showed the same expression profile, including genes involved in storage of amino acids (VSP), glucosinolate production (CYP79), polyamine biosynthesis (ADC2), and defense (PDF1.2) [20].
• Analysis of the expression profiles of PR-1, BGL2, PR-5 and PDF1.2 in eds14, eds15, and eds16 revealed differences from the wild type for all the lines [21].
• The Arabidopsis vegetative storage protein (AtVSP) and plant defense-related proteins thionin (Thi2.1) and defensin (PDF1.2) have previously been shown to accumulate in response to JA induction [22].

Analytical, diagnostic and therapeutic context of PDF1.2

• The transgenic plants containing the PDF1.2-based promoter-reporter construct will provide useful tools for future genetic dissection of this novel systemic signalling pathway [23].

References