Elucidation of the morphology of rice lodicules and the mechanism of spikelet opening and closing using X-ray micro-CT

Research Project

Project/Area Number	22K19175
Research Category	Grant-in-Aid for Challenging Research (Exploratory)
Allocation Type	Multi-year Fund
Review Section	Medium-sized Section 39:Agricultural and environmental biology and related fields
Research Institution	Nagoya University
Principal Investigator	Oi Takao 名古屋大学, 生命農学研究科, 助教 (60752219)
Co-Investigator(Kenkyū-buntansha)	上口美弥子 (田中美弥子) 名古屋大学, 生物機能開発利用研究センター, 教授 (70377795) 山内卓樹名古屋大学, 生物機能開発利用研究センター, 准教授 (50726966)
Project Period (FY)	2022-06-30 – 2024-03-31
Project Status	Completed (Fiscal Year 2023)
Budget Amount *help	¥6,370,000 (Direct Cost: ¥4,900,000、Indirect Cost: ¥1,470,000) Fiscal Year 2023: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000) Fiscal Year 2022: ¥5,070,000 (Direct Cost: ¥3,900,000、Indirect Cost: ¥1,170,000)
Keywords	イネ / 開花 / 3D形態解析 / コンピュータートモグラフィー / X線顕微鏡 / CTスキャン / デジタルマイクロスコープ / 閉花 / 植物ホルモン
Outline of Research at the Start	イネ穎花の開花を司る微小な花器官である鱗被の立体像を、非破壊・迅速・簡便な三次元解析が可能なX線マイクロCT(コンピュータ断層撮影)法を用いて解析し、籾の開閉という動的な現象を捉え、その作用機序を明らかにする。電子顕微鏡観察のノウハウを応用することでX線CT装置の持つ空間分解能を最大限に高めて細胞レベルの情報も取得しながら鱗被の全容を理解する。併せて、生鮮試料をX線装置内で生け花状に保持して穎花を経時スキャンし、鱗被による開閉の動的な作用について時間軸を加えた理解にも挑む。
Outline of Final Research Achievements	To elucidate the mechanism of the dynamic action of opening and closing of rice spikelets, we analyzed the three-dimensional(3D) images of minute lodicules using X-ray micro-CT (computed tomography), which allows non-destructive, rapid, and simple 3D analysis. First, the specimens were fixed, dehydrated, and dried in accordance with the method for preparations for electron microscopy, and then scanned at high resolution using X-ray CT for 3D analysis, allowing quantitative comparison of the tissue shape of the lodicules and the size and number of the cells that compose them before and after anthesis. We also performed live imaging, in which the panicles were placed in a flower arrangement and scanned in the X-ray CT over time, obtaining 3D data of the tissue shape of the spikelets in as little as one minute, and elucidating the changes in the morphology and spatial arrangement of the lodicules and glumes from opening to closing of spikelets.
Academic Significance and Societal Importance of the Research Achievements	研究成果の概要に示したように、X線マイクロCTを活用し、未知であったイネ鱗被の形態変化を組織・細胞レベルで捉え、イネ穎花の開閉メカニズムの解明に一定の寄与ができた。また、開発してきた観察法は今後のイネ研究だけでなく、広く植物の研究に貢献できる汎用性のある技術体系となると期待される。