Phytoalexin Accumulation in Arabidopsis thaliana during the Hypersensitive Reaction to Pseudomonas syringae pv syringae

Abstract

Inoculation of leaves of Arabidopsis thaliana (L.) Heynh. with the wheat pathogen, Pseudomonas syringae pv syringae, resulted in the expression of the hypersensitive reaction and in phytoalexin accumulation. No phytoalexin accumulation was detected after infiltration of leaves with a mutant of P. s. syringae deficient in the ability to elicit a hypersensitive reaction; with the crucifer pathogen, Xanthomonas campestris pv campestris; or with 10 milimolar potassium phosphate buffer (pH 6.9). Phytoalexin accumulation was correlated with the restricted in vivo growth of P. s. syringae. A phytoalexin was purified by a combination of reverse phase flash chromatography, thin layer chromatography, followed by reverse phase high performance liquid chromatography. The Arabidopsis phytoalexin was identified as 3-thiazol-2'-yl-indole on the basis of ultraviolet, infrared, mass spectral, 1H-nuclear magnetic resonance, and '3C-nuclear magnetic resonance data.Phytoalexins are low mol wt, antimicrobial compounds of plant origin that accumulate after inoculation with a plant pathogen (14). A number of observations support the hypothesis that phytoalexins play a role in the defense response of plants to pathogens. Phytoalexins are absent in healthy tissues and accumulate after infection by fungal (18,24,30) or bacterial (9, 1 1) pathogens in monocotyledonous plants (24) as well as in dicotyledonous plants (9,18,30). Phytoalexins have been demonstrated to accumulate rapidly at the site of attempted infection in sufficient quantities to inhibit the in vitro growth of fungi (18,30) and bacteria (9). Virulence of the fungus Nectria haematococca on pea is correlated with the ability to detoxify the phytoalexin pisatin (28). Furthermore, transformation of Cochliobolus heterostrophus with the gene encoding pisatin demethylase allowed this maize patho-

ArabidopsisPEN3/PDR8, an ATP Binding Cassette Transporter, Contributes to Nonhost Resistance to Inappropriate Pathogens That Enter by Direct Penetration

“…Because pen3 but not pen2 mutants develop chlorotic and necrotic patches with E. cichoracearum infections, we further propose that another enzyme(s), acting in parallel with PEN2, generates a related toxin(s) that is also exported by PEN3. To date, one phytoalexin, camalexin, has been identified in Arabidopsis (Tsuji et al, 1992). However, it is unlikely that this compound is solely responsible for the phenotypes conferred by pen3, because phytoalexin-deficient3 (pad3) and pad4 mutants lack the phenotype conferred by pen (data not shown).…”

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

“…In Arabidopsis, PAD4 also modulates accumulation of camalexin (Tsuji et al, 1992;Rogers et al, 1996). Camalexin levels increase in GPA-infested Arabidopsis leaves.…”

Phytoalexins produced in the leaves of Capsella bursa-pastoris (shepherd’s purse)

“…challenged with Pseudomonas syringae pv. syringaevan Hall (Tsuji et al 1992). Because of récent interest in thèse compounds Gross 1993;Pedras et al 1997;Tsuji et al 1993), we report on the isolation of thèse compounds, and a new related compound, from shepherd's purse [Capsella bursa-pastoris (L.) Medic] challenged with A. brassicae.…”

“…Some research has been done on the rôle of camalexin in the host-defense Systems of C. sativa and A. thaliana (Conn et al 1988(Conn et al , 1994Jejelowo et al 1991;Rogers et al 1996;Tsuji et al 1992). Camalexin is the major phytoalexin in C. bursapastoris and is associated with high degrees of résistance to A. brassicae and A. brassicicola (Conn étal.…”