Phytohormone Involvement in the Ustilago maydis- Zea mays Pathosystem: Relationships between Abscisic Acid and Cytokinin Levels and Strain Virulence in Infected Cob Tissue

• Published in: PloS one 2015-06, Vol.10 (6), p.e0130945-e0130945
• Main Authors: Morrison, Erin N, Emery, R J Neil, Saville, Barry J
• Format: Article
• Language: English
• Subjects: Abscisic acid; Abscisic Acid - physiology; Analysis; Biosynthesis; Cell division; Chromatography; Corn; Cytokinins; Cytokinins - physiology; Fungi; Gene expression; Genetic engineering; Glucosides; Health aspects; High performance liquid chromatography; Host-Pathogen Interactions - physiology; Infection; Infections; Ionization; Kinases; Liquid chromatography; Mass spectrometry; Mass spectroscopy; Metabolism; Molecular Structure; Pathogenesis; Phytohormones; Plant hormones; Plant Stems - microbiology; Plant tissues; Plant Tumors - microbiology; Plants (botany); Smut; Tissue analysis; Tissues; Tumors; Ustilago - pathogenicity; Ustilago maydis; Virulence; Virulence (Microbiology); Zea mays; Zea mays - microbiology; Zea mays - physiology
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0130945

Ustilago maydis is the causative agent of common smut of corn. Early studies noted its ability to synthesize phytohormones and, more recently these growth promoting substances were confirmed as cytokinins (CKs). Cytokinins comprise a group of phytohormones commonly associated with actively dividing tissues. Lab analyses identified variation in virulence between U. maydis dikaryon and solopathogen infections of corn cob tissue. Samples from infected cob tissue were taken at sequential time points post infection and biochemical profiling was performed using high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI MS/MS). This hormone profiling revealed that there were altered levels of ABA and major CKs, with a marked reduction in CK glucosides, increases in methylthiol CKs and a particularly dramatic increase in cisZ CK forms, in U. maydis infected tissue. These changes were more pronounced in the more virulent dikaryon relative to the solopathogenic strain suggesting a role for cytokinins in moderating virulence during biotrophic infection. These findings highlight the fact that U. maydis does not simply mimic a fertilized seed but instead reprograms the host tissue. Results underscore the suitability of the Ustilago maydis- Zea mays model as a basis for investigating the control of phytohormone dynamics during biotrophic infection of plants.