Reactive oxygen species (ROS) produced naturally during cellular metabolism often cause oxidative damage to cells. However, these molecules also play an important role in normal cellular signaling. While ROS are established as essential signaling molecules in various organisms, their precise role in basic plant development and morphogenesis remains unclear.
A family of enzymes known as NADPH oxidases (NOXs) generates ROS that act as physiologically important signaling molecules. In plants, the NOX enzymes are known as respiratory burst oxidase homologs (RBOHs), which are implicated in diverse physiological processes. However, their contribution to plant development, including cell proliferation and ordered morphogenesis, has remained insufficiently understood.
To address this gap, a team of researchers, led by Professor Kazuyuki Kuchitsu from the Department of Applied Biological Science, Tokyo University of Science (TUS), Japan, conducted a study. The study also highlighted the liverwort model, Marchantia polymorpha, to understand the role of RBOHs in plant development and morphogenesis. The study was published online on May 8, 2026, and appeared in Volume 36, Issue 10 of the journal Current Biology on May 18, 2026. The TUS research team included Professor Ryuichi Nishihama, Yuto Yamashita, Yuki Hagiwara, Dr. Kenji Hashimoto, Seigo Hoshino, and Mizuki Ogawa. This collaborative effort also involved Dr. Hidemasa Suzuki from Tohoku University, Japan; Dr. Megumi Iwano from Kyoto University, Japan; and Dr. Toshiki Ishikawa from Saitama University, Japan.
“We have previously shown, using plants such as Arabidopsis thaliana, that RBOHs play important roles in processes such as root hair and pollen tube tip growth. However, it has been difficult to determine how RBOH-derived ROS contribute to the more fundamental processes that shape the plant body, including cell division, growth, differentiation, and morphogenesis. This is mainly because most plants possess multiple RBOH genes with complementary and partially redundant functions. The liverwort M. polymorpha, which has only two RBOH genes, provided an ideal model for addressing this question,” explains Prof. Kuchitsu.
The team used CRISPR-Cas9-based genome editing technology to disrupt the two RBOH genes, Mp RBOHA and Mp RBOHB . To further clarify their functions, the researchers combined genetic approaches, including conditional knockout and conditional knockdown analyses, with pharmacological treatments, live-cell imaging, electron microscopy, and transcriptomic analyses. This multifaceted approach allowed them to examine how the loss or reduction of RBOH-derived ROS affects cell division, differentiation, cell-surface integrity, and morphogenesis during plant development.
While plants with a single gene mutation showed abnormal growth patterns, simultaneous disruption of both genes led to severe developmental defects, including marked growth inhibition and a failure to form organized tissue structures, ultimately resulting in the formation of a slowly growing, disorganized cell mass resembling a callus. The study also highlighted both overlapping and specialized functions of the genes. While both were expressed in the meristematic regions, containing actively dividing cells, during the vegetative state, Mp RBOHB expression was also uniquely observed in the root-like rhizoid cells.
The study also highlights the role of RBOH-derived ROS in cell proliferation. Reduced RBOH activity led to a reduced number of actively dividing cells in the growing regions of the plant. Chemical removal of ROS resulted in similar growth defects, indicating that ROS signaling is crucial for normal vegetative growth.
Beyond its role in cell division, RBOH-derived ROS signaling is also vital in maintaining normal cell shape and tissue organization. In plants lacking RBOH function, the developing cells were abnormally swollen and irregular, lacking the spatial order needed to form organized tissues. These findings also highlight the important role of RBOHs in maintaining the integrity of the cuticle and cell wall. In mutants lacking RBOH function, defects in cell-wall integrity were observed, along with cuticle impairment. Because the cuticle acts as a protective barrier, its impairment was associated with leakage of cell-wall components outside the plant body.
Furthermore, a comprehensive gene expression analysis revealed that ROS are closely associated with hormone- and redox-related gene expression and with transcriptional regulation involved in cell differentiation programs, which are essential for the development of mature, patterned plant tissues.
“These findings reshape how we view ROS signaling in plant biology. Rather than acting only as stress-related molecules, ROS appear to function as core developmental signals that help plants coordinate cell proliferation, tissue integrity, and differentiation. This work also provides insight into early land plant evolution, suggesting that controlled ROS production may have helped plants acquire complex, organized multicellular body structures,” explains Prof. Kuchitsu.
The findings may also contribute to future applications in agriculture and biotechnology. By clarifying how ROS-producing enzymes coordinate plant growth and morphogenesis, this study could inform future strategies for improving crop resilience for food security in harsh environments, optimizing plant architecture to enhance urban agriculture efficiency, and advancing plant tissue culture and plant regeneration technologies. Overall, this research seeks to inspire innovations in agriculture and biotechnology, aiming for a more stable and sustainable future intertwined with nature.
Reference
DOI: https://doi.org/10.1016/j.cub.2026.04.016
About The Tokyo University of Science
Tokyo University of Science (TUS) is a well-known and respected university, and the largest science-specialized private research university in Japan, with four campuses in central Tokyo and its suburbs and in Hokkaido. Established in 1881, the university has continually contributed to Japan's development in science through inculcating the love for science in researchers, technicians, and educators.
With a mission of “Creating science and technology for the harmonious development of nature, human beings, and society," TUS has undertaken a wide range of research from basic to applied science. TUS has embraced a multidisciplinary approach to research and undertaken intensive study in some of today's most vital fields. TUS is a meritocracy where the best in science is recognized and nurtured. It is the only private university in Japan that has produced a Nobel Prize winner and the only private university in Asia to produce Nobel Prize winners within the natural sciences field.
Website: https://www.tus.ac.jp/en/mediarelations/
About Professor Kazuyuki Kuchitsu from Tokyo University of Science
Professor Kazuyuki Kuchitsu is associated with the Faculty of Science and Technology, Department of Applied Biological Science, Tokyo University of Science, Japan. He earned his Ph.D. from The University of Tokyo in 1990. His research area includes plant molecular biology and plant physiology, with a particular emphasis on intracellular and systemic signal transduction mechanisms. His pioneering studies have elucidated how the spatiotemporal dynamics of second messengers, including calcium ions and reactive oxygen species (ROS), regulate plant immunity, environmental stress responses, growth, and development. Actively promoting interdisciplinary research, he has recently expanded his research activities into the field of plasma plant science. He has authored more than 140 peer-reviewed scientific publications to date, which have been cited more than 25,000 times. He is a member of several academic societies, including the Botanical Society of Japan and Japanese Society of Plant Physiologists. In 2026, he received the Plant and Cell Physiology Best Paper Award.
Professor Kazuyuki Kuchitsu
Faculty of Science and Technology, Department of Applied Biological Science, Tokyo University of Science, Japan
Email: kuchitsu@rs.tus.ac.jp
Current Biology
Experimental study
Not applicable
Indispensable roles of RBOH-mediated ROS production in development and morphogenesis of Marchantia polymorpha
18-May-2026
The authors declare no competing interests.