Cytosolic Glutamine Synthetase GS1;3 Is Involved in Rice Grain Ripening and Germination.

Area of Science:

• Plant Biology
• Biochemistry
• Agricultural Science

Background:

• Glutamine synthetase (GS) catalyzes ammonium assimilation into glutamine.
• Cytosolic GS1 isoforms are present in plants, with rice GS1;3 showing high expression in seeds.
• The specific role of rice GS1;3 in plant growth and yield requires further investigation.

Purpose of the Study:

• To investigate the physiological roles of rice GS1;3 in plant growth and yield.
• To understand the function of GS1;3 during seed germination and grain filling, particularly under nitrogen-deficient conditions.

Main Methods:

• Isolation and analysis of Tos17 insertion lines for rice GS1;3 mutants.
• Quantification of nitrogen, amino acid, and ammonium content in mutant and wild-type rice grains.
• Evaluation of spatiotemporal GS1;3 expression, plant growth, and yield in hydroponic and field conditions.
• Tracing foliar nitrogen flux using stable isotopes during grain filling.

Main Results:

• Loss of GS1;3 function retarded seed germination and led to glutamate accumulation in seeds.
• GS1;3 mutants exhibited a reduced ripening ratio and decreased nitrogen efflux under nitrogen deficiency.
• GS1;3 expression was observed during early germination and in the vascular tissue and aleurone layer of developing grains.

Conclusions:

• Rice GS1;3 plays a unique role in the early stages of seed germination.
• GS1;3 is essential for efficient grain filling under nitrogen-deficient conditions.
• The findings underscore the importance of GS1;3 for rice yield and development.