Maize host requirements for Ustilago maydis tumor induction

Area of Science:

• Plant Pathology
• Developmental Biology
• Molecular Genetics

Background:

• Ustilago maydis is a biotrophic pathogen that induces tumors in maize (Zea mays L.) by manipulating host development.
• Tumor formation occurs in both vegetative and floral tissues, suggesting a broad impact on plant growth pathways.

Purpose of the Study:

• To investigate the spatial and developmental factors influencing Ustilago maydis-induced tumor formation in maize tassels.
• To identify host genetic and hormonal factors that modulate susceptibility to U. maydis.

Main Methods:

• Fungal injection into immature maize tassels to observe tumor development.
• Analysis of male-sterile maize mutants with defects in anther development.
• Hormonal treatments (methyl jasmonate, brassinosteroid) and analysis of hormone-related mutants (Dwarf8, anther ear1).
• Examination of Knotted1 mutant for effects on tumor size.

Main Results:

• Tumor formation in tassels followed a specific progression mirroring cell division patterns in spikelets.
• Male-sterile mutants and hormonal treatments created sterile zones resistant to tumor formation.
• Gibberellin signaling (Dwarf8 mutant) was crucial for tassel tumor development, while gibberellin content (anther ear1) and leaf growth regulators (Knotted1) modulated tumor size.

Conclusions:

• Host growth potential and tissue identity are key factors in Ustilago maydis's ability to redirect differentiation and induce tumors.
• Specific developmental stages and hormonal pathways in maize anthers are critical for susceptibility to U. maydis.