[P4] Crop Genetics and Physiology

[P4-19] A Metabolite Profiling to Explore the Physiological Function of Short Panicle 1 during Panicle Formation of Rice

Yifan Lin¹, Ryutaro Morita¹, Masaki Okamura², Junko Yamagishi¹, ^○Naohiro Aoki¹ (1.Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan, 2.Central Region Agricultural Research Center, National Agriculture and Food Research Organization, Japan)

The rice inflorescence architecture, which is determined by the length and number of branches, has a great agronomic value and therefore also attracted much attention in the past years. The Short Panicle 1 (SP1) is categorized in the Nitrate Transporter 1/Peptide Transporter gene family and the knock-out mutant (sp1) displays a short-panicle phenotype with fewer rachis-branches. Previous studies reported that SP1 functions in the vasculature of young panicles after primordia initiation, but the molecular mechanism underlying its effect on panicle formation remains unclear. In the present study, the sp1 mutant and wild type (cv. "Nipponbare") were grown in paddy fields and compared to investigate the physiological function of SP1. From 28 to 14 days before the heading date, we sampled a 3-cm bottom part of stem including young panicle, and conducted a metabolite profiling by using an ion chromatography and a high performance liquid chromatography. Among sugar phosphates and carboxylic acids involved in the primary metabolism, mannose-6-phosphate (M6P) and 2-oxoglutaric acid (2OG) were accumulated in the sp1 mutant at significantly higher levels, compared with the wild type. M6P can be converted into GDP-mannose, which is related to cell wall formation. 2OG is known to be a key metabolite in amino acid synthesis, providing the carbon skeleton for nitrogen assimilation. Thus, the higher accumulation of M6P and 2OG may imply that the cell wall formation and nitrogen assimilation pathways are inhibited in sp1 mutant.