Preferential induction of 20S proteasome subunits during elicitation of plant defense reactions: towards the characterization of “plant defense proteasomes”

• Published in: The international journal of biochemistry & cell biology Vol. 35; no. 5; pp. 637 - 650
• Main Authors: Suty, Lydie, Lequeu, José, Lançon, Allan, Etienne, Philippe, Petitot, Anne-Sophie, Blein, Jean-Pierre
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01.05.2003; Elsevier
• Subjects: 20S proteasome; Algal Proteins - pharmacology; Blotting, Northern; Blotting, Western; Cysteine Endopeptidases - biosynthesis; Cysteine Endopeptidases - physiology; Defense inducible subunits; Electrophoresis, Gel, Two-Dimensional; Elicitins; Enzyme Induction; Fungal Proteins; Gene Expression; Life Sciences; Mixed Function Oxygenases - biosynthesis; Multienzyme Complexes - biosynthesis; Multienzyme Complexes - physiology; Nicotiana - enzymology; Nicotiana - virology; Peptide Hydrolases - biosynthesis; Plant defense reactions; Plant Leaves - enzymology; Proteasome Endopeptidase Complex; Proteins; Systemic acquired resistance; Tobacco Mosaic Virus - pathogenicity; Systemic acquired resistance; DAB; Plant defense reactions; SAR; Defense inducible subunits; din; HR; 20S proteasome; DPI; Elicitins; REPONSE DE LA PLANTE
• ISSN: 1357-2725; 1878-5875
• DOI: 10.1016/S1357-2725(02)00386-2

Plants have evolved efficient mechanisms to resist pathogens. The earliest defense response is the hypersensitive response (HR) considered as the main step leading to plant systemic acquired resistance (SAR) that protects the whole plant against a large spectrum of pathogens. We showed previously that elicitation of defense reactions in tobacco cells by cryptogein, a proteinaceous elicitor of plant defense reactions, leads to a rapid and differential accumulation of transcripts corresponding to genes encoding defense-induced (din) subunits of 20S proteasome: β1din, α3din and α6din. Here, expression of these three subunits was investigated by Northern blotting and by Western blotting using specific antibodies synthesized against two peptides deduced from the β1din, α3din or α6din encoding sequence. Kinetics of mRNA and protein accumulation in various defense models showed a simultaneous accumulation of β1din, α3din and α6din corresponding mRNAs and proteins only in plants developing a systemic acquired resistance. Inhibition by diphenyleneiodonium of the oxidative burst induced in defense reactions blocked the expression of β1din, α3din and α6din. Using 2D gel electrophoresis and Western blotting, we showed multiple spots for each induced subunit suggesting the possible existence of multigenic families confirmed by genomic DNA analysis. These results suggest a complex regulation of induced subunits tightly correlated with the activation of plant defense reactions. β1din, α3din and α6din subunits could probably replace the corresponding constitutive subunits in 20S proteasome leading to “plant defense proteasomes” which could play an important role in plant defense reactions.