The Barley MLO Modulator of Defense and Cell Death Is Responsive to Biotic and Abiotic Stress Stimuli

• Published in: Plant physiology (Bethesda) 2002-07, Vol.129 (3), p.1076-1085
• Main Authors: Pietro Piffanelli, Zhou, Fasong, Casais, Catarina, James Orme, Birgit Jarosch, Ulrich Schaffrath, Collins, Nicholas C., Panstruga, Ralph, Schulze-Lefert, Paul
• Format: Article
• Language: English
• Subjects: Airborne microorganisms; Alleles; Apoptosis - genetics; Barley; Biological and medical sciences; Cell biochemistry; Cell death; Cell physiology; Cell Wall - metabolism; Epidermal cells; Fundamental and applied biological sciences. Psychology; Fungi - growth & development; Gene Expression Regulation, Developmental - drug effects; Gene Expression Regulation, Plant - drug effects; Generalities. Disease free stocks; Genotypes; Hordeum - genetics; Hordeum - metabolism; Hordeum - microbiology; Hydrogen peroxide; Hydrogen Peroxide - metabolism; Immunity, Innate - genetics; Inoculation; Leaves; Mesophyll cells; Mildews; Mortality; Mutation; Paraquat; Paraquat - pharmacology; Phytopathology. Animal pests. Plant and forest protection; Plant Diseases - genetics; Plant Diseases - microbiology; Plant Leaves - genetics; Plant Leaves - metabolism; Plant physiology and development; Plant Proteins - genetics; Plant Proteins - metabolism; Plants; Plants Interacting with Other Organisms; RNA Splicing - genetics; Stress, Mechanical
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.010954

Lack of the barley (Hordeum vulgare) seven-transmembrane domain MLO protein confers resistance against the fungal pathogen Blumeria graminis f. sp. hordei (Bgh). To broaden the basis for MLO structure/function studies, we sequenced additional mlo resistance alleles, two of which confer only partial resistance. Wild-type MLO dampens the cell wall-restricted hydrogen peroxide burst at points of attempted fungal penetration of the epidermal cell wall, and in subtending mesophyll cells, it suppresses a second oxidative burst and cell death. Although the Bgh-induced cell death in mlo plants is spatially and temporally separated from resistance, we show that the two processes are linked. Uninoculated mutant mlo plants exhibit spontaneous mesophyll cell death that appears to be part of accelerated leaf senescence. Mlo transcript abundance increases in response to Bgh, rice (Oryza sativa) blast, wounding, paraquat treatment, a wheat powdery mildew-derived carbohydrate elicitor, and during leaf senescence. This suggests a broad involvement of Mlo in cell death protection and in responses to biotic and abiotic stresses.