ABSTRACT
Plant activators are agrochemicals that activate the plant immune system, thereby enhancing disease resistance. Due to their prophylactic and durable effects on a wide spectrum of diseases, plant activators can provide synergistic crop protection when used in combination with traditional pest controls. Although plant activators have achieved great success in wet-rice farming practices in Asia, their use is still limited. To isolate novel plant activators applicable to other crops, we screened a chemical library using a method that can selectively identify immune-priming compounds. Here, we report the isolation and characterization of three diuretics, bumetanide, bendroflumethiazide and clopamide, as immune-priming compounds. These drugs upregulate the immunity-related cell death of Arabidopsis suspension-cultured cells induced with an avirulent strain of Pseudomonas syringae pv. tomato in a concentration-dependent manner. The application of these compounds to Arabidopsis plants confers disease resistance to not only the avirulent but also a virulent strain of the pathogen. Unlike salicylic acid, an endogenous phytohormone that governs disease resistance in response to biotrophic pathogens, the three diuretic compounds analyzed here do not induce PR1 or inhibit plant growth, showing potential as lead compounds in a practical application.
Subject(s)
Arabidopsis/immunology , Disease Resistance/drug effects , Diuretics/pharmacology , Plant Immunity/drug effects , Arabidopsis/cytology , Arabidopsis/microbiology , Arabidopsis Proteins/genetics , Bendroflumethiazide/chemistry , Bendroflumethiazide/pharmacology , Bumetanide/chemistry , Bumetanide/pharmacology , Cell Death/drug effects , Cell Death/genetics , Cell Death/immunology , Cells, Cultured , Clopamide/chemistry , Clopamide/pharmacology , Disease Resistance/genetics , Disease Resistance/immunology , Diuretics/chemistry , Dose-Response Relationship, Drug , Gene Expression Regulation, Plant/drug effects , Host-Pathogen Interactions/drug effects , Host-Pathogen Interactions/immunology , Molecular Structure , Plant Diseases/genetics , Plant Diseases/immunology , Plant Diseases/microbiology , Plant Immunity/genetics , Pseudomonas syringae/drug effects , Pseudomonas syringae/immunology , Pseudomonas syringae/physiology , Reverse Transcriptase Polymerase Chain Reaction , Transcription Factors/geneticsABSTRACT
A first-derivative spectrophotometric method, using a 'zero-crossing' technique of measurement has been used for determining clopamide-pindolol mixture in tablets. In the first-derivative mode the zero-crossing points of clopamide and pindolol occur at 272.6 and 262.4 nm, respectively. The relative ease offered by this technique for the quantification of these drugs with closely overlapping bands was demonstrated. The linearity of the calibration curves was satisfactory (r = 0.9998) and the precision (RSD%) better than 1.89. Detection limits were 0.50 and 0.44 micrograms ml-1 for pindolol and clopamide, respectively. No spectral interferences from tablet excipients were found. Applications are given for the assay of commercial tablets and content uniformity test. The procedures proved to be suitable for rapid and reliable quality control.