Yongqi He, Jinping Cheng, Ying He, Bin Yang, Yanhao Cheng, Can Yang, Hongsheng Zhang, Zhoufei Wang

 Plant Biotechnology Journal; 27 June 2018 - https://doi.org/10.1111/pbi.12979

 Abstract

Seed vigor is an imperative trait for the direct seeding of rice. Isopropylmalate synthase (IPMS) catalyzes the committed step of leucine (Leu) biosynthesis, but its effect on seed vigor remains unclear. In this study, rice OsIPMS1 and OsIPMS2 was cloned, and the roles of OsIPMS1 in seed vigor were mainly investigated. OsIPMS1 and OsIPMS2 catalyze Leu biosynthesis, and Leu feedback inhibits their IPMS activities. Disruption of OsIPMS1resulted in low seed vigor under various conditions, which might be tightly associated with the reduction of amino acids in germinating seeds. Eleven amino acids that associated with stress tolerance, GA biosynthesis and tricarboxylic acid (TCA) cycle were significantly reduced in osipms1 mutants compared with those in wide type (WT) during seed germination. Transcriptome analysis indicated that a total of 1,209 differentially expressed genes (DEGs) were altered in osipms1a mutant compared with WT at the early germination stage, wherein most of the genes were involved in glycolysis/gluconeogenesis, protein processing, pyruvate, carbon, fructose and mannose metabolism. Further analysis confirmed that the regulation of OsIPMS1 in seed vigor involved in starch hydrolysis, glycolytic activity and energy levels in germinating seeds. The effects of seed priming were tightly associated with the mRNA levels of OsIPMS1 in priming seeds. The OsIPMS1 might be used as a biomarker to determine the best stop time‐point of seed priming in rice. This study provides novel insights into the function of OsIPMS1 on seed vigor and should have practical applications in seed priming of rice.

See https://onlinelibrary.wiley.com/doi/abs/10.1111/pbi.12979

Figure 1: Activities of OsIPMS1 and OsIPMS2 in rice. (a) Pathway for Leu biosynthesis. (b)  Purification of the expressed GST Tag OsIPMS1 and OsIPMS 2 protein. (c, d)  OsIPMS1 and OsIPMS 2 activities were identified by directly measuring absorbance at 412 nm. (e, f) The  Activities of  OsIPMS1  and OsIPMS2 are subjected to Leu feedback inhibition.