A mutation in Arabidopsis that leads to constitutive expression of systemic acquired resistance.

Abstract

Systemic acquired resistance (SAR) is a nonspecific defense response in plants that is associated with an increase in the endogenous level of salicylic acid (SA) and elevated expression of pathogenesis-related (PR) genes. To identify mutants involved in the regulation of PR genes and the onset of SAR, we transformed Arabidopsis with a reporter gene containing the promoter of a p-l,3-glucanase-encoding PR gene (BGLP) and the coding region of &glucuronidase (GUS).The resulting transgenic line (BGLP-GUS) was mutagenized, and the M2 progeny were scored for constitutive GUS activity. We report the characterization of one mutant, c p r l &onstitutive expresser of PR genes), that was identified in this screen and shown by RNA gel blot analysis also to have elevated expression of the endogenous PR genes BGLP, PR-1, and PR-5. Genetic analyses indicated that the phenotype conferred by c p r l is caused by a single, recessive nuclear mutation and is suppressed in plants producing a bacterial salicylate hydroxylase, which inactivates SA. Furthermore, biochemical analysis showed that the endogenous level of SA is elevated in the mutant. Finally, the c p r l plants were found to be resistant to the fungal pathogen Peronospora parasitica NOC02 and the bacterial pathogen Pseudomonas syringae pv maculicola ES4326, which are virulent in wild-type BGLP-GUS plants. Because the c p r l mutation is recessive and associated with an elevated endogenous level of SA, we propose that the CPRl gene product acts upstream of SA as a negative regulator of SAR.

Involvement of Salicylate and Jasmonate Signaling Pathways in Arabidopsis Interaction with Fusarium graminearum

“…Both these well characterized mutants constitutively express the PR1 gene and accumulate high levels of SA (Fig. 3B; Bowling et al 1994; Shah et al 2001). Disease severity was lower in F. graminearum inoculated leaves of the Arabidopsis cpr5 and ssi2 mutants than the WT plant (Fig.…”

“…These results along with the ability of biologically activated SAR to enhance resistance against F. graminearum , suggested that SA may have an important role in controlling the severity of disease caused by F. graminearum . However, it should be noted that along with SA, JA signaling is also hyperactive in the cpr5 mutant (Bowling et al 1994; Jing et al 2007) and could potentially influence the interaction between cpr5 and F. graminearum . To further test the involvement of SA signaling in controlling F. graminearum infection, disease severity was compared between F. graminearum inoculated WT and the sid2 mutant plant.…”

“…The ssi2 mutant and the NahG transgenic (Shah et al 1999; 2001) are in the Arabidopsis thaliana accession Nössen, the sid2-2 (Wildermuth et al 2001), cpr5 (Bowling et al 1994), npr1-1 (Cao et al 1994), jar1-1 (Staswick et al 1998), wrky18 (Xu et al 2006) and opr3 mutants, and the NPR1 (OE) and WRKY18 (OE) transgenic lines (Cao et al 1998; Xu et al 2006) are in the Arabidopsis accession Columbia. Arabidopsis plants were cultivated at 22°C in a growth chamber programmed for 14-h light (100μE m −2 s −1 ) and 10-h dark cycle.…”

Synergistic Activation of Defense Responses in Arabidopsis by Simultaneous Loss of the GSL5 Callose Synthase and the EDR1 Protein Kinase

“…Specifically, we performed quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) analysis on PR - 1 (At2g14610, a marker for SA-dependent gene expression; (Bowling et al, 1994)) , PBS3 (At5g13320, involved in regulation of SA levels; (Nobuta et al, 2007)), ICS1 (At1g74710, involved in SA biosynthesis; (Wildermuth et al, 2001)), AtERF1 (At4g17500, an APETALA2/ETHYLENE RESPONSE FACTOR transcription factor family member that is strongly inducible by methyl jasmonate (Nemhauser et al, 2006) and which is upregulated in the edr1 mutant; (Wawrzynska et al, 2008)), SRG1-like (At4g10500, a stress-induced ascorbate oxidase upregulated in pmr4-1 after powdery mildew infection (Nishimura et al, 2003)), and an endochitinase (At2g43570, also upregulated in pmr4-1 following powdery mildew infection (Nishimura et al, 2003) and by the SA-responsive transcription factor WRKY70 (Li et al, 2004)). RNA was isolated from rosette leaves of 4.5 week old plants grown in the absence of pathogens under 9 hr days, which was approximately 1 week after lesions began appearing on edr1eed3 plants.…”

Transcriptional Profiling of Rice Treated with MoHrip1 Reveal the Function of Protein Elicitor in Enhancement of Disease Resistance and Plant Growth

“…Leaf tissue treated with MoHrip1 or buffer was collected, weighed and frozen in liquid nitrogen. For each sample, 0.1 g of the frozen tissue was extracted and quantitated for free SA, as described previously (Bowling et al, 1994). In brief, the tissue was ground into powder and homogenized in 1 mL of methanol-H 2 O-acetic acid (80:19:1).…”