The Pathway and Regulation of Salicylic Acid Biosynthesis in Probenazole-Treated Arabidopsis

Abstract

Probenazole (PBZ; 3-allyloxy-1,2-benzisothiazole-1,1-dioxide) is a highly effective chemical inducer of systemic-acquired resistance (SAR). It has been used widely to protect rice plants against the rice blast fungus Magnaporthe grisea. Previous studies have shown that PBZ induces SAR through enhanced accumulation of salicylic acid (SA). Plants synthesize SA by either a pathway that uses phenylalanine as substrate or another that involves isochorismate. To clarify how SA is produced in PBZ-treated Arabidopsis, we examined the expression patterns and enzyme activities of phenylalanine ammonia lyase (PAL) and isochorismate synthase (ICS), which are the main components of the phenylalanine and isochorismate pathways, respectively. PBZ exposure significantly improved the accumulation of SA and increased ICS activity. In the sid2-2 mutant, which has a defect in ICS1, PBZ had no effect on the level of endogenous SA or activity of ICS. In contrast, PAL activity and the expression of most PAL genes were down-regulated by such treatment in wild-type plants. These results suggest that SA is mainly synthesized via the ICS-mediated pathway in Arabidopsis.

TCP transcription factors are critical for the coordinated regulation of ISOCHORISMATE SYNTHASE 1 expression in Arabidopsis thaliana

“…Previously, we have shown that probenazole, an effective inducer of systemic acquired resistance, efficiently induces ICS1 expression in Arabidopsis (Yu et al, 2010). In the present study, we used the yeast one-hybrid (Y1H) system to screen for upstream direct regulators of ICS1, and identified TCP8, a transcription factor of the TEOSINTE BRANCHED1/CYCLOIDEA/PCF (TCP) family.…”

“…Free SA was then extracted and quantified from approximately 350 mg tissue per sample using HPLC analysis as previously described (Yu et al, 2010). Briefly, tissues were homogenized and sonicated twice in 3 ml of 100% methanol.…”

Eugenol enhances the resistance of tomato against tomato yellow leaf curl virus

“…Total contents of SA (the sum of free and conjugated SA) in tomato leaves were detected according to Jin Yu et al with some modification. 32 Harvested tomato leaf materials (∼1 g) were ground in liquid nitrogen and homogenized briefly in a mortar after addition of 3 mL methanol (90% v/v). After centrifugation for 15 min at 4 • C at × 12 000 g, the pellet was re-extracted with 3 mL 100% methanol.…”

Berberine induces resistance against tobacco mosaic virus in tobacco

“…Plants synthesize SA via either a pathway that uses phenylalanine as the substrate or one that involves isochorismate (ICS). The route has phenylalanine ammonia lyase (PAL) and chorismate mutase1 (CM1) as catalytic enzymes, and BA2H hydroxylates benzoic acid to SA at the final step . Another route has isochorismate synthase (ICS1) and PBS3 as key factors .…”

“…The route has phenylalanine ammonia lyase (PAL) and chorismate mutase1 (CM1) as catalytic enzymes, and BA2H hydroxylates benzoic acid to SA at the final step. 31 Another route has isochorismate synthase (ICS1) and PBS3 as key factors. [32][33][34] Transcript levels of PAL and CM1 involved in the PAL route increased markedly by 6.778-and 5.246-fold, respectively.…”