Nucleobase-ascorbate transporter OsNAT9 regulates seed vigor and drought tolerance by modulating ascorbic acid...

Area of Science:

• Plant Biology
• Molecular Biology
• Biochemistry

Background:

• Seed aging and drought stress significantly reduce crop yield and seed viability.
• Ascorbic acid (AsA) plays a critical role in mitigating oxidative stress and maintaining seed quality.
• Understanding the molecular mechanisms of AsA transport is crucial for improving crop stress tolerance.

Purpose of the Study:

• To identify and characterize the role of the rice nucleobase-ascorbate transporter, OsNAT9, in seed vigor and drought tolerance.
• To elucidate the function of OsNAT9 in ascorbic acid (AsA) homeostasis and reactive oxygen species (ROS) scavenging.
• To investigate the potential of OsNAT9 as a target for enhancing crop stress adaptation and seed longevity.

Main Methods:

• Gene knockout and overexpression of OsNAT9 in rice.
• Measurement of AsA concentration and ROS levels in wild-type, mutant, and overexpressed lines.
• Protoplast secretion assays and microscale thermophoresis to confirm transporter function.
• Analysis of seed dormancy, starch structure, and embryo vigor under aging and drought conditions.

Main Results:

• OsNAT9 knockout significantly reduced seed vigor and drought tolerance, linked to decreased AsA levels and increased ROS accumulation.
• Exogenous AsA application and breaking seed dormancy partially restored vigor in Osnat9 mutants.
• OsNAT9 functions as a cytomembrane-localized efflux transporter, mediating AsA secretion and maintaining redox homeostasis.
• Overexpression of OsNAT9 enhanced drought tolerance and AsA levels while reducing ROS accumulation.

Conclusions:

• OsNAT9 plays a dual role in regulating seed vigor and drought tolerance by controlling AsA efflux and ROS scavenging.
• Maintaining AsA homeostasis through OsNAT9 is essential for seed longevity and stress adaptation in rice.
• OsNAT9 represents a promising target for genetic engineering to improve crop resilience to environmental stresses and extend seed viability.