ORIGINAL RESEARCH Abscisic acid-mediated sugar responses are essential for vegetative desiccation tolerance in the liverwort Marchantia polymorpha Nobiza Khatun 1 | Akihisa Shinozawa 2 | Kosaku Takahashi 3 | Hideyuki Matsuura 4 | Akida Jahan 1 | Mousona Islam 1 | Md Masudul Karim 1 | Rahul Sk 2 | Mikako Yoshikawa 5 | Kimitsune Ishizaki 5 | Yoichi Sakata 2 | Daisuke Takezawa 1 1 Graduate School of Science and Engineering, Saitama University, Saitama, Japan 2 Department of Bioscience, Faculty of Life Sciences, Tokyo University of Agriculture, Tokyo, Japan 3 Department of Nutritional Science, Faculty of Applied Bioscience, Tokyo University of Agriculture, Tokyo, Japan 4 Division of Fundamental, AgriScience Research, Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan 5 Graduate School of Science, Kobe University, Kobe, Hyogo, Japan Correspondence Daisuke Takezawa, Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan. Email: takezawa@mail.saitama-u.ac.jp Present address Mousona Islam, Biological Research Division, Bangladesh Council of Scientific and Industrial Research (BCSIR), Dhaka 1205, Bangladesh. Funding information Ministry of Education, Culture, Sports, Science and Technology, Grant/Award Numbers: 18H04774, 19H03247, 20K06680, JP15H05955 Edited by I. Willick Abstract Low-molecular-weight sugars serve as protectants for cellular membranes and macromolecules under the condition of dehydration caused by environmental stress such as desiccation and freezing. These sugars also affect plant growth and develop- ment by provoking internal signaling pathways. We previously showed that both sugars and the stress hormone abscisic acid (ABA) enhance desiccation tolerance of gemma, a dormant propagule of the liverwort Marchantia polymorpha. To determine the role of ABA in sugar responses in liverworts, we generated genome-editing lines of M. polymorpha ABA DEFICIENT 1 (MpABA1) encoding zeaxanthin epoxidase, which catalyzes the initial reaction toward ABA biosynthesis. The generated Mpaba1 lines that accumulated only a trace amount of endogenous ABA showed reduced desiccation tolerance and reduced sugar responses. RNA-seq analysis of sucrose-treated gemmalings of M. polymorpha revealed that expression of a large part of sucrose-induced genes was reduced in Mpaba1 compared to the wild-type. Furthermore, Mpaba1 accumulated smaller amounts of low-molecular-weight sugars in tissues upon sucrose treatment than the wild-type, with reduced expres- sion of genes for sucrose synthesis, sugar transporters, and starch-catabolizing enzymes. These results indicate that endogenous ABA plays a role in the regulation of the positive feedback loop for sugar-induced sugar accumulation in liverworts, enabling the tissue to have desiccation tolerance. 1 | INTRODUCTION Low molecular-weight sugars such as sucrose are fundamental com- pounds serving as energy and carbon sources to support plant growth Nobiza Khatun and Akihisa Shinozawa equally contributed to this study and share first authorship. Received: 28 October 2022 Revised: 13 March 2023 Accepted: 22 March 2023 DOI: 10.1111/ppl.13898 Physiologia Plantarum This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2023 The Authors. Physiologia Plantarum published by John Wiley & Sons Ltd on behalf of Scandinavian Plant Physiology Society. Physiologia Plantarum. 2023;175:e13898. wileyonlinelibrary.com/journal/ppl 1 of 10 https://doi.org/10.1111/ppl.13898