RESEARCH NEWS STORY
April 23, 2024
Chiba University
Nagoya University
Konan University

Unveiling the Molecular Functions ofLipid Droplet Proteins in Arabidopsis thaliana Leaves
Researchers characterize leaf lipid droplet proteins, shedding light on their potential roles inlipid movement and fat production catalysis
Lipid droplets (LDs) serve as storage organelles found in plant leaves and seeds. While thefunctions of seed LD proteins in lipid metabolism are well understood, many leaf LD
proteins remain unidentified. Scientists have now identified leaf LD proteins and uncovered
their localization within Arabidopsis thaliana, shedding light on their potential roles in lipid
metabolism and fat production. Their observations reveal that these proteins areassociated with LD movement and lipid metabolism.

Image title: A schematic representation of multiple unique plant proteins localized in lipid droplets on the leaves.
Image caption: A new study shows that lipid droplets in the leaves contain plant proteins such as different
myosin binding proteins involved in intracellular movement, and several enzymes responsible for furancontaining fatty acid biosynthesis—a type of fatty acid production in plants—highlighting previously
undiscovered potential molecular functions.
Image credit: Takashi L. Shimada from Chiba University
Image Source link: https://www.frontiersin.org/files/Articles/1331479/fpls-15-1331479-HTMLr1/image_m/fpls-15-1331479-g006.jpg
Image license: CC BY 4.0

Lipids are biomolecules essential for the proper functioning of the living cell, ranging fromcomprising cell membranes to forming integral components of cell signaling pathways. Plant
cells possess cell subcellular structures or organelles called lipid droplets (LDs) in the leaves
and seeds, which store excess lipids (fats).
Recent studies have shown that LDs also localize unique plant proteins that perform essential
molecular functions. For example, seed LDs localize plant proteins called oleosins, which help
seeds weather freezing temperatures and germinate properly. With an expanding body of
proof that LDs are not just organelles for carbon storage but may also perform essential
molecular functions, a group of researchers from Japan sought to understand the role of therelatively unexplored leaf LDs. Associate Professor Takashi L. Shimada, an LD expert affiliatedwith Chiba University, explains the motivation behind their research, “We have a limited
understanding of the functions of leaf LDs—why do plant leaves accumulate LDs at all? Webelieve the answer to this fundamental question would also contribute to lipid production
technology.”
In a new pioneering study published in Frontiers in Plant Science on 01 March 2024, Dr.
Shimada and his research group showed that leaf LDs localized myosin binding proteins
essential for intracellular movements and enzymes that catalyze furan fatty acidbiosynthesis—a type of fat production in living cells—highlighting the potential and previously
undiscovered molecular functions of LDs. This research was led by Dr. Shimada, who isassociated with the Graduate School of Horticulture, Plant Molecular Science Center, andResearch Center for Space Agriculture and Horticulture at Chiba University, Japan. His
research group also involved Mr. Yuto Omata from the Faculty of Horticulture, Chiba
University, who is the first author of this study, along with Dr. Emi Mishiro-Sato, lecturer atWorld Premier International Research Center Initiative-Institute of Transformative BioMolecules, Nagoya University, and Dr. Ikuko Hara-Nishimura and Dr. Haruko Ueda from theFaculty of Science and Engineering, Konan University in Japan.
The researchers used an Arabidopsis plant model mutated to accumulate LDs in the leaves
called Arabidopsis thaliana mutant high sterol ester 1. Dr. Shimada adds, “This Arabidopsis
plant mutant model also serves as a valuable resource for further studying the leaf LD
proteome.”
Further, the researchers isolated these leaf LDs and used mass spectrometry to identify
associated proteins. They found 3,206 candidate proteins. Furthermore, they focused on 31
candidate proteins to test associated behavior in leaf LDs. They attached a fluorescent marker
to these proteins to facilitate microscopic observations.
The fluorescence microscopy revealed the presence of MYOSIN BINDING PROTEIN14(MYOB14) and two uncharacterized proteins in the leaf LDs under investigation. Further
examination narrowed down the MYOB family members localized to leaf LDs: MYOB1, MYOB2,MYOB3, and MYOB5. The researchers also identified the two uncharacterized proteins as
resembling enzymes for furan fatty acid biosynthesis, suggesting a potential link between leaf
LDs and the type of fatty acid production.

Despite the progress made in this study, Dr. Shimada cautions about the need for furtherstudies on leaf LDs, “We need to identify additional leaf LD proteins to resolve the molecularand physiological functions of leaf LDs.”
Nonetheless, the study paves the way for future research in leaf LDs—a relatively untappedplant resource—that could revolutionize lipid production and associated industries, all thanks
to the efforts of Dr. Shimada and his team.
About Associate Professor Takashi L. Shimada
Dr. Takashi L. Shimada works in the Graduate School of Horticulture, Plant Molecular Science
Center, and Research Center for Space Agriculture and Horticulture at Chiba University, Japan.
Dr. Shimada investigates the intracellular structure of plants, especially lipid droplets. His
research aims to comprehensively understand lipid storage in plants and enhance plant lipid
production for potential application as a food resource. He has co-authored more than 20
reputed publications and is a member of multiple academic societies, including the Japanese
Association of Plant Lipid Researchers and The Phytopathological Society of Japan.
Funding:
The author(s) declare that financial support was received for the research, authorship, and/orpublication of this article. This work was supported by Grants-in-Aid for Scientific Researchfrom the Japan Society for the Promotion of Science (JSPS) to TS (nos. 19K05809 and23K17986), HU (nos. 19K06732 and 18H05496), and IH-N (no. 15H05776); Kato Memorial
Bioscience Foundation (to TS); a SUNBOR GRANT from the Suntory Foundation for Life
Sciences (to TS); Takeda Science Foundation (to TS); a research grant from The Yanmar
Environmental Sustainability Support Association to TS; Inamori Foundation (to TS); JGC-SScholarship Foundation (to TS); the Leading Initiative for Excellent Young Researchers(LEADER) from the Ministry of Education, Culture, Sports, Science and Technology in Japan(MEXT) to TS (no. J16HJ00026); the Phytochemical Plant Molecular Science of Strategic
Priority Research Promotion Program from Chiba University (to TS and KS); and the Hirao TaroFoundation of KONAN GAKUEN for Academic Research (to HU and IH-N).
Reference:
Title of original paper: Lipid droplets in Arabidopsis thaliana leaves contain myosin-binding
proteins and enzymes associated with furan-containing fatty acid biosynthesis
Authors: Yuto Omata1, Reina Sato1, Emi Mishiro-Sato2, Keiko Kano2, Haruko Ueda3, Ikuko
Hara-Nishimura3, and Takashi L. Shimada1,4,5,6*
Affiliations:
1
Faculty of Horticulture, Chiba University, Matsudo, Japan
2World Premier International Research Center Initiative-Institute of Transformative BioMolecules, Nagoya University, Nagoya, Japan
3
Faculty of Science and Engineering, Konan University, Kobe, Japan
4
Graduate School of Horticulture, Chiba University, Matsudo, Japan
5
Plant Molecular Science Center, Chiba University, Chiba, Japan
6
Research Center for Space Agriculture and Horticulture, Chiba University, Matsudo, Japan
Journal: Frontiers in Plant Science
DOI: 10.3389/fpls.2024.1331479