Elucidation of defense‐related signaling responses to spot blotch infection in bread wheat (Triticum aestivum L.)

• Published in: The Plant journal : for cell and molecular biology 2016-04, Vol.86 (1), p.35-49
• Main Authors: Sahu, Ranabir, Sharaff, Murali, Pradhan, Maitree, Sethi, Avinash, Bandyopadhyay, Tirthankar, Mishra, Vinod K., Chand, Ramesh, Chowdhury, Apurba K., Joshi, Arun K., Pandey, Shree P.
• Format: Article
• Language: English
• Subjects: Ascomycota - cytology; Ascomycota - physiology; Biosynthesis; Bipolaris sorokiniana; Crop diseases; Cyclopentanes - metabolism; Ethylenes - metabolism; gene annotation; Gene Expression Regulation, Plant; Genotypes; Humid climates; Inbreeding; Metabolites; Molecular Sequence Annotation; Oxylipins - metabolism; phenolic acids; Phenols; phytohormone signaling; plant defense; Plant Diseases - immunology; Plant Growth Regulators - metabolism; Plant Immunity; Plant Leaves - genetics; Plant Leaves - immunology; Plant Leaves - physiology; Plant pathology; Plant resistance; recombinant inbred line; salicylic acid; Salicylic Acid - metabolism; Signal Transduction; spot blotch; Triticum - genetics; Triticum - immunology; Triticum - physiology; Triticum aestivum; Wheat
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/tpj.13149

Summary Spot blotch disease, caused by Bipolaris sorokiniana, is an important threat to wheat, causing an annual loss of ~17%. Under epidemic conditions, these losses may be 100%, yet the molecular responses of wheat to spot blotch remain almost uncharacterized. Moreover, defense‐related phytohormone signaling genes have been poorly characterized in wheat. Here, we have identified 18 central components of salicylic acid (SA), jasmonic acid (JA), ethylene (ET), and enhanced disease susceptibility 1 (EDS1) signaling pathways as well as the genes of the phenylpropanoid pathway in wheat. In time‐course experiments, we characterized the reprogramming of expression of these pathways in two contrasting genotypes: Yangmai #6 (resistant to spot blotch) and Sonalika (susceptible to spot blotch). We further evaluated the performance of a population of recombinant inbred lines (RILs) by crossing Yangmai#6 and Sonalika (parents) and subsequent selfing to F10 under field conditions in trials at multiple locations. We characterized the reprogramming of defense‐related signaling in these RILs as a consequence of spot blotch attack. During resistance to spot blotch attack, wheat strongly elicits SA signaling (SA biogenesis as well as the NPR1‐dependent signaling pathway), along with WRKY33 transcription factor, followed by an enhanced expression of phenylpropanoid pathway genes. These may lead to accumulation of phenolics‐based defense metabolites that may render resistance against spot blotch. JA signaling may synergistically contribute to the resistance. Failure to elicit SA (and possibly JA) signaling may lead to susceptibility against spot blotch infection in wheat. Significance Statement Wheat provides 20% of our calories but its production, especially in warm and humid climates, faces a severe challenge from spot blotch disease. The molecular response of wheat to spot blotch infection remains nearly uncharacterized. Here, we characterized 18 central genes of defense‐related signaling pathways in susceptible and resistant wheat genotypes and suggest that salicylic acid biosynthesis and signaling play a major role in mediating resistance against spot blotch infection.