A mutation causing proline requirement in Zea mays

Area of Science:

• Plant Genetics
• Molecular Biology
• Biochemistry

Background:

• Conditional seedling lethal mutants offer insights into essential metabolic pathways in plants.
• Identifying auxotrophic mutants in higher plants is challenging due to developmental complexities.
• The genetic control of amino acid biosynthesis is crucial for plant growth and development.

Purpose of the Study:

• To describe a novel monogenic recessive endosperm mutant in Zea mays.
• To investigate the genetic basis of a conditional lethal phenotype.
• To establish the first reported case of a strict amino acid requirement in Zea mays.

Main Methods:

• Phenotypic characterization of a monogenic recessive mutant.
• In vitro embryo culture on media supplemented with varying proline concentrations.
• Analysis of genetic blocks in biosynthetic pathways.

Main Results:

• The mutant exhibits a conditional seedling lethal phenotype.
• In vitro culture with proline rescues the lethal phenotype, with efficiency proportional to proline concentration.
• Normal growth is restored at 160 mg/l proline.
• Data strongly suggest a genetic block in the proline biosynthetic pathway.

Conclusions:

• The mutant, 'pro', possesses a genetic defect in proline biosynthesis, creating an obligate requirement for exogenous proline.
• This represents the first documented instance of a strict amino acid auxotrophy in Zea mays.
• The findings contribute to understanding the challenges and implications of isolating auxotrophs in higher plants.