Seed vigor is an important trait for the direct seeding of rice.
Isopropylmalate synthase (IPMS) is known to catalyze the committed step of
leucine (Leu) biosynthesis, but its effect on seed vigor remains unclear.
Yongqi He, together with his colleagues, studied the roles of rice OsIPMS1
and OsIPMS2 in seed vigor. Both OsIPMS1 and OsIPMS2 are known to catalyze
Leu biosynthesis, and Leu feedback inhibits their IPMS activities.
Disruption of OsIPMS1 resulted in low seed vigor under various conditions,
which might be associated with the reduction of amino acids in germinating
seeds. Eleven amino acids that associated with stress tolerance, GA
biosynthesis, and tricarboxylic acid cycle were also significantly reduced
in osipms1 mutants compared with those in wildtypes during seed germination.
Analysis indicated that a total of 1,209 differentially expressed genes were
altered in the osipms1 mutant compared with wildtypes at the early
germination stage. Most of the genes were involved in glycolysis, protein
processing, and mannose metabolism. Further analysis confirmed that the role
of OsIPMS1 in seed vigor is involved in starch hydrolysis, glycolytic
activity, and energy levels in germinating seeds.
This study provides novel insights into the function of OsIPMS1 on seed