Salicylic Acid Mediated by the Oxidative Burst Is a Key Molecule in Local and Systemic Responses of Cotton Challenged by an Avirulent Race of Xanthomonas campestris pvmalvacearum

Abstract

We analyzed the production of reactive oxygen species, the accumulation of salicylic acid (SA), and peroxidase activity during the incompatible interaction between cotyledons of the cotton (Gossypium hirsutum) cv Reba B50/Xanthomonas campestris pv malvacearum (Xcm) race 18. SA was detected in petioles of cotyledons 6 h after infection and 24 h post inoculation in cotyledons and untreated leaves. The first peak of SA occurred 3 h after generation of superoxide (O 2 ⅐؊ ), and was inhibited by infiltration of catalase. Peroxidase activity and accumulation of SA increased in petioles of cotyledons and leaves following H 2 O 2 infiltration of cotyledons from 0.85 to 1 mM. Infiltration of 2 mM SA increased peroxidase activity in treated cotyledons and in the first leaves, but most of the infiltrated SA was rapidly conjugated within the cotyledons. When increasing concentrations of SA were infiltrated 2.5 h post inoculation at the beginning of the oxidative burst, the activity of the apoplastic cationic O 2 ⅐؊ -generating peroxidase decreased in a dose-dependent manner. We have shown that during the cotton hypersensitive response to Xcm, H 2 O 2 is required for local and systemic accumulation of SA, which may locally control the generation of O 2 ⅐؊ . Detaching cotyledons at intervals after inoculation demonstrated that the signal leading to systemic accumulation of SA was emitted around 3 h post inoculation, and was associated with the oxidative burst. SA produced 6 h post infection at HR sites was not the primary mobile signal diffusing systemically from infected cotyledons.

Vitamin B1 Functions as an Activator of Plant Disease Resistance

“…Although different subsets of the defense signaling cascade are expressed in each pathosystem during pathogen recognition and infection, most defense mechanisms are common to the different systems. Oxidative bursts and ion fluxes have been observed in numerous incompatible plant-pathogen interactions, and secondary signaling messengers are up-regulated systemically prior to the expansion of local lesions (Bolwell et al, 1995;Grant et al, 2000;Martinez et al, 2000;Kachroo et al, 2003). Furthermore, treatment with SA or its commercial derivative benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) inhibits disease progress in many compatible plant-microbe interactions Gorlach et al, 1996;Lawton et al, 1996;Wurms et al, 1999;Kohler et al, 2002;Bokshi et al, 2003;Achuo et al, 2004) and prevents the infection of plant roots with root-parasitic weeds (Sauerborn et al, 2002).…”

Aktivitas Enzim Peroksidase Bawang Merah Yang Diintroduksi Dengan Bakteri Endofit Dan Tahan Terhadap Penyakit Hawar Daun Bakteri (Xanthomonas Axonopodis Pv. Allii)

“…Selain itu, peningkatan aktivitas enzim peroksidase dipengaruhi oleh adanya serangan patogen. Aktivitas peroksidase sebagai penanda terjadinya pengimbasan yang bersifat lokal maupun sistemik pada tanaman (Martinez et al, 2000).…”

Salicylic acid in the induction of resistance to beet seedling damping-off and antifungal activity against Fusarium sp., in vitro

“…Salicylic acid (SA) is an elicitor with the physiological role of analyzing in plants, especially in the defense against pathogens, it being transported via the phloem to the non-infected plant parts, mainly in the form of methyl salicylate and even serving as a signal to neighbouring plants (MARTINEZ et al, 2000).…”