Elucidation of biosynthetic pathway of cell wall and cuticle in developing fruit - Dynamism of starch degradation products in tomato fruit

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K07586
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Horticultural science
• Research Institution: University of Tsukuba
• Principal Investigator: Matsukura Chiaki 筑波大学, 生命環境系, 教授 (60361309)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 果実 / トマト / デンプン / AGPase / 糖 / ペクチン / ガラクツロン酸 / クチクラ

Outline of Final Research Achievements

This research project aimed to elucidate the physiological roles of starch accumulated in tomato fruit. In order to understand the metabolic pathway of starch and its utilization during fruit ripening, the starch-defect transgenic lines in which the expression of ADP-glucose pyrophosphorylase was suppressed were analyzed in aspects of the cell wall polysaccharides, fruit cuticle and fruit firmness. Results showed that starch is metabolized to UDP-D-galacturonic acid which is a major component of cell wall pectin as well as soluble sugars. In addition, it was revealed that in the starch-defect lines, the firmness of red-ripe fruit and amount of cuticle decreased. All taken together, the present research demonstrated that starch degradation products are utilized not only for soluble sugars but also biosynthesis of cell wall polysaccharides and fruit cuticle, then affect fruit firmness in red-ripe fruit.

Free Research Field

園芸生理学、遺伝育種学、糖・アミノ酸・有機酸代謝、環境ストレス応答

Academic Significance and Societal Importance of the Research Achievements

デンプンはそれ自体食味を持たないため、従来の果実生理学研究では殆ど注目されておらず、漠然と、成熟期に可溶性糖に代謝される、と説明されてきた。本研究ではデンプン蓄積欠損遺伝子組換えトマトを用いて、果実におけるデンプンの代謝的役割を解析し、デンプン分解産物が成熟中に可溶性糖だけでなくペクチンやクチクラ生合成に関与し、果実硬度にも影響するという結果を得た。デンプンから細胞壁生合成やクチクラに向かう代謝経路はこれまで報告されておらず、果実生理学分野では大きな学術的意義を持つと考えられる。また、食感、果実硬度など商業的価値を持つ形質のメカニズム解明にも資することから相応の社会的意義を有すると考えられる。