A temporal and spatial contribution of asparaginase to asparagine catabolism during development of rice grains

Yui Yabuki, Miwa Ohashi, Fumi Imagawa, Keiki Ishiyama, Marcel Pascal Beier, Noriyuki Konishi, Toshiko Umetsu-Ohashi, Toshihiko Hayakawa, Tomoyuki Yamaya, Soichi Kojima

    Research output: Contribution to journalArticlepeer-review

    11 Citations (Scopus)

    Abstract

    Background: Asparagine is one of the most dominant organic nitrogen compounds in phloem and xylem sap in a wide range of plant species. Asparaginase (ASNase; EC, 3.5.1.1) catabolizes asparagine into aspartate and ammonium; therefore, it is suggested to play a key role in asparagine metabolism within legume sink organs. However, the metabolic fate of asparagine in source and sink organs during rice seed production remains to be elucidated. Therefore, the main objective of this study is to investigate the asparagine metabolism in a temporal and spatial manner during rice seed production. Results: For this purpose, the expression of genes involved in asparagine catabolism, such as asparaginase1 (OsASNase1) and 2 (OsASNase2), were quantitatively measured, and contents of asparagine, aspartate and ammonium ions were determined in sink and source organs during spikelet ripening. Quantitative real-time PCR and in situ localization studies determined that OsASNase2 is expressed in the dorsal vascular bundles and nucellar projection of developing grains, as well as in mesophyll and phloem companion cells of senescent flag leaves. Amino acid measurements revealed that the aspartate concentration is higher than asparagine in both source and sink organs. Conclusion: This work suggests that asparaginase dependent asparagine catabolism occurred not only in sink but also in source organs.

    Original languageEnglish
    Article number3
    JournalRice
    Volume10
    Issue number1
    DOIs
    Publication statusPublished - Dec 1 2017

    Keywords

    • Asparaginase
    • Asparagine
    • Nitrogen
    • Rice
    • Translocation

    ASJC Scopus subject areas

    • Agronomy and Crop Science
    • Soil Science
    • Plant Science

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