PT - JOURNAL ARTICLE AU - D.S. Kishor AU - Choonseok Lee AU - Dongryung Lee AU - Jelli Venkatesh AU - Jeonghwan Seo AU - Joong Hyoun Chin AU - Zhuo Jin AU - Soon-Kwan Hong AU - Jin-Kwan Ham AU - Hee-Jong Koh TI - Novel allelic variant of <em>Lpa1</em> gene associated with a significant reduction in seed phytic acid content in rice (<em>Oryza sativa</em> L.) AID - 10.1101/493981 DP - 2018 Jan 01 TA - bioRxiv PG - 493981 4099 - http://biorxiv.org/content/early/2018/12/11/493981.short 4100 - http://biorxiv.org/content/early/2018/12/11/493981.full AB - In plants, myo-inositol-1,2,3,4,5,6-hexakisphosphate (InsP6), also known as phytic acid (PA), is a major component of organic phosphorus (P), and accounts for up to 85% of the total P in seeds. In rice (Oryza sativa L.), PA mainly accumulates in rice bran, and chelates mineral cations, resulting in mineral deficiencies among brown rice consumers. Therefore, considerable efforts have been focused on the development of low PA (LPA) rice cultivars. In this study, we performed genetic and molecular analyses of OsLpa1, a major PA biosynthesis gene, in Sanggol, a low PA mutant variety developed via chemical mutagenesis of Ilpum rice cultivar. Genetic segregation and sequencing analyses revealed that a recessive allele, lpa1-3, at the OsLpa1 locus (Os02g0819400) was responsible for a significant reduction in seed PA content in Sanggol. The lpa1-3 gene harboured a point mutation (C623T) in the fourth exon of the predicted coding region, resulting in threonine (Thr) to isoleucine (Ile) amino acid substitution at position 208 (Thr208Ile). Three-dimensional analysis of Lpa1 protein structure indicated that myo-inositol 3-monophosphate [Ins(3)P1] kinase binds to the active site of Lpa1, with ATP as a cofactor for catalysis. Furthermore, the presence of Thr208 in the loop adjacent to the entry site of the binding pocket suggests that Thr208Ile substitution is involved in regulating enzyme activity via phosphorylation. Therefore, we propose that Thr208Ile substitution in lpa1-3 reduces Lpa1 enzyme activity in Sanggol, resulting in reduced PA biosynthesis.