title: Overexpression of a Gene Involved in Phytic Acid Biosynthesis Substantially Increases Phytic Acid and Total Phosphorus in Rice Seeds.
abstract: The manipulation of seed phosphorus is important for seedling growth and environmental P sustainability in agriculture. The mechanism of regulating P content in seed, however, is poorly understood. To study regulation of total P, we focused on phytic acid (inositol hexakisphosphate; InsP₆) biosynthesis-related genes, as InsP₆ is a major storage form of P in seeds. The rice (Oryza sativa L.) low phytic acid mutant lpa1-1 has been identified as a homolog of archael 2-phosphoglycerate kinase. The homolog might act as an inositol monophosphate kinase, which catalyzes a key step in InsP₆ biosynthesis. Overexpression of the homolog in transgenic rice resulted in a significant increase in total P content in seed, due to increases in InsP₆ and inorganic phosphates. On the other hand, overexpression of genes that catalyze the first and last steps of InsP₆ biosynthesis could not increase total P levels. From the experiments using developing seeds, it is suggested that the activation of InsP₆ biosynthesis in both very early and very late periods of seed development increases the influx of P from vegetative organs into seeds. This is the first report from a study attempting to elevate the P levels of seed through a transgenic approach.
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan. tagashira0812@gmail.com.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Tagashira
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan. 1176hours@gmail.com.
authors.forename: Tomoe
authors.initials: T
authors.lastname: Shimizu
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan. masanyobu@yahoo.co.jp.
authors.forename: Masanobu
authors.initials: M
authors.lastname: Miyamoto
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan. asho3@mail.ecc.u-tokyo.ac.jp.
authors.forename: Sho
authors.initials: S
authors.lastname: Nishida
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan. ayosida@mail.ecc.u-tokyo.ac.jp.
authors.forename: Kaoru T
authors.initials: KT
authors.lastname: Yoshida
keywords: Oryza sativa L.; ectopic expression; mineral element; molecular breeding; phosphorus; phytic acid; seed; translocation