[植物生理] 離層酸可調控植物木質部纖維的分化。 20191113 Development

An essential role for abscisic acid in the regulation of xylem fibre differentiation

Liam Campbell, J. Peter Etchells, Matthew Cooper, Manoj Kumar and Simon R. Turner

Abstract

Division of the cambial cells and their subsequent differentiation into xylem and phloem drives radial expansion of the hypocotyl. Following the transition to reproductive growth, a phase change occurs in the Arabidopsis hypocotyl. During this second phase, the relative rate of xylem production is dramatically increased compared with that of phloem, and xylem fibres that contain thick secondary cell walls also form. Using two different genetic backgrounds and different environmental conditions, we identified a set of core transcriptional changes that is associated with the switch to the second phase of growth in the hypocotyl. Abscisic acid (ABA) signalling pathways are significantly over-represented in this set of core genes. Reverse genetic analysis demonstrated that mutants that are defective in ABA biosynthesis enzymes exhibited significantly delayed fibre production without affecting the xylem:phloem ratio, and that these effects can be reversed by the application of ABA. The altered morphology is also reflected at the transcript level, with a reduced expression of marker genes that are associated with fibre formation in aba1 mutants. Taken together, the data reveal an essential role for ABA in the regulation of fibre formation.

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離層酸在木質不纖維分化的調控上扮演了一個必須的角色

摘要

形成層細胞的分裂以及後續的分化成為木質部與韌皮部，是植物莖增加厚度的推手。阿拉伯芥在進入繁殖生長後（抽花芽），下胚軸會經歷一個時期的轉換。在這個第二個時期，木質部的增生會遠超過韌皮部的增加速度，而但有次級細胞壁的木質部纖維也會在這個時期生成。利用兩種不同基因體背景的植物以及不同環境的晴望下，我們在下胚軸鑑定出一系列與第二時期變化相關的核心轉錄改變。離層酸（ABA）訊息途徑在這群核心基因中，很明顯的有多於預測的基因參與在其中。利用基因突變的方式發現，在離層酸合成基因上有缺失的植株，有很明顯纖維生成較緩慢的現象，但是這個現象並沒有影響到韌皮部與木質部的比例。並且，這個現象可以以外加離層酸的方式來克服。這個改變的性狀同樣也反應了轉錄表現的量，在aba1突變株中，主要的與纖維形成的標誌基因也都有減少的現象。總合以上，我們的資料顯示離層酸在調控纖維生成的機制上扮演了一個必要的角色。

原文出處 https://dev.biologists.org/content/145/21/dev161992.long