Answer found to the long-standing question of size control of plant leaf organs

August 6, 2021

Contributing to understanding of the body size determination mechanism of plants and animals and eventually to the higher yield of crops

A joint research group of Tokyo Gakugei University, RIKEN CSRS, and the University of Tokyo focused on the phenomenon of “compensated cell enlargement (CCE)”. The enlargement of cell size is seen when the number of cells decreases due to some mutations, which appears to maintain the areas of plant leaves. The mechanism of this phenomenon has been a mystery since 2002. The fugu5 mutant of the model plant Arabidopsis thaliana, which the research group has originally isolated, has approximately one-half the number of cells that make up the cotyledons compared to the wild type, resulting in “CCE”, whereby the size of individual leaf cells is increased.

Using fugu5 mutant, and with full use of molecular genetics, the group elucidated the mechanism of CCE. As a result, the group newly found that auxin, a plant hormone synthesized from indole-3-butyric acid (IBA), is important for CCE in fugu5 and that intracellular signaling of auxin drives the significant increase in cell size. This discovery is a breakthrough about auxin, a plant hormone discovered by Darwin in 1880. The study has shown that fluctuations of endogenous auxin are involved in the fine tuning of cotyledon area, while demonstrating that the regulatory mechanisms of auxin concentration are fundamentally important for plant organ development.

These findings represent a seminal contribution not only for understanding the sizes of plant organs but also for understanding plant productivity. The study can also be an important contribution towards understanding the mechanisms of body and organ size control for all living organisms beyond plant and animal kingdoms. In addition, these findings may be useful for agricultural studies aiming to increase biomass and crop yields, through the acceleration of plant leaf growth.

Original article
PLOS genetics doi:10.1371/journal.pgen.1009674
H. Tabeta, S. Watanabe, K. Fukuda, S. Gunji, M. Asaoka, M. Yokota Hirai, M.Seo, H. Tsukaya, A. Ferjani,
"An Auxin Signaling Network Translates Low-Sugar-State Input into Compensated Cell Enlargement in the fugu5 Cotyledon".
Hiromitsu Tabeta; Student Trainee
Masami Hirai; Team Leader
Metabolic Systems Research Team
Mitsunori Seo; Unit Leader
Dormancy and Adaptation Research Unit