Proline accumulation in a barley mutant resistant to trans-4-hydroxy-L-proline

Area of Science:

• Plant Physiology
• Molecular Genetics
• Agricultural Science

Background:

• Proline analogues can inhibit plant growth, but this effect is often reversible by proline.
• Understanding plant responses to proline analogues and stress is crucial for crop improvement.

Purpose of the Study:

• To investigate barley (Hordeum vulgare L.) embryo growth inhibition by proline analogues.
• To identify and characterize barley mutants resistant to trans-4-hydroxyproline.
• To assess the physiological and genetic basis of proline accumulation and stress tolerance in these mutants.

Main Methods:

• Sterile culture of mature barley embryos with proline analogues.
• Sodium azide mutagenesis and selection of resistant mutants.
• Genetic analysis of resistance and proline content determination.
• Water stress experiments using polyethylene glycol (PEG).

Main Results:

• Five proline analogues inhibited barley embryo growth, with inhibition relieved by proline.
• Mutant R5201 exhibited resistance to trans-4-hydroxyproline, L-thiazolidine-4-carboxylic acid, and trans-3-hydroxy-L-proline.
• Progeny of R5201 showed up to a six-fold increase in soluble proline content in leaves.
• Mutant leaves accumulated proline more rapidly under water stress conditions.
• Resistance to trans-4-hydroxyproline was attributed to a single, partially dominant nuclear gene.

Conclusions:

• Mutations conferring resistance to proline analogues can lead to increased proline accumulation.
• Enhanced proline levels in barley mutants correlate with improved water stress tolerance.
• A single nuclear gene controls trans-4-hydroxyproline resistance and influences proline metabolism.