Non-proline-accumulating rice mutants resistant to hydroxy-L-proline

Area of Science:

• Plant genetics
• Biochemistry
• Agricultural science

Background:

• Hydroxy-L-proline (Hyp) is an amino acid that can induce stress responses in plants.
• Understanding plant resistance mechanisms to Hyp is crucial for improving crop resilience.
• Genetic and biochemical bases of Hyp resistance in rice (Oryza sativa L.) are not fully elucidated.

Purpose of the Study:

• To characterize the biochemical and genetic basis of hydroxy-L-proline (Hyp) resistance in rice mutants.
• To investigate the role of free proline accumulation in Hyp resistance.
• To identify the genetic control of Hyp resistance in selected rice lines.

Main Methods:

• Selection of Hyp-resistant rice mutants (HYP 101, HYP 202, HYP 203) from an ethylene imine mutagenized population.
• Germination and culture of rice seeds and seedlings with varying concentrations of Hyp (10(-4)∼10(-3) M) for 10 days.
• Analysis of free amino acid composition in seeds and 15-day-old seedlings of mutants and the original variety.
• Genetic analysis to determine the inheritance pattern of Hyp resistance.

Main Results:

• Three rice mutants (HYP 101, HYP 202, HYP 203) exhibited differential resistance to Hyp compared to the 'Nipponbare' variety.
• HYP 101 demonstrated the highest level of Hyp resistance among the selected mutants.
• Amino acid composition differed between mutants and the original variety, but free proline accumulation was not observed in any line.
• Hyp resistance was consistently transmitted as a single recessive nuclear gene (hpr) in each mutant line.

Conclusions:

• The identified rice mutants provide a valuable resource for studying Hyp resistance mechanisms.
• The recessive gene (hpr) controlling Hyp resistance in these mutants does not appear to operate through free proline accumulation.
• Further research into the biochemical pathways regulated by the hpr gene is warranted to understand Hyp tolerance in rice.