Tokyo Gakugei University

BioMeca

Rikkyo University

ENS de Lyon/ Kumamoto University IROAST

Graduate School of Science, The University of Tokyo

Overview

A research group led by Associate Professor Ferjani Ali of Tokyo Gakugei University, Dr. Pascale Milani and Ms. Gaël Runel of BioMeca, ENS de Lyon, Professor Goro Horiguchi of Rikkyo University, Professor Olivier Hamant of ENS de Lyon/Kumamoto University IROAST, Professor Shinichiro Sawa of Kumamoto University, and Professor Yuichi Tsukatani of Kumamoto University has been studying the structure of the stem as an organelle. Professor Shinichiro Horiguchi of Rikkyo University, Professor Olivier Hamant of ENS de Lyon/IROAST, Professor Yuichi Tsukatani of The University of Tokyo, and their research group studied the mechanism that maintains the stem as an integrated organ structure. Based on the theory of tissue tension, they considered the epidermal tissue to be important, and as a result of tackling this problem, they succeeded in clearly demonstrating that the tough epidermis is the tag that receives the internal pressure of the stem.

The skin that covers our entire body is a familiar tissue that helps us sense the seasons and protects us from external stimuli and bacterial infections. Plants are no exception. The entire plant body is surrounded by a single layer of tissue called the epidermis, which is said to protect the plant from invasion by pathogens and viruses, as well as from drying out. Unlike animal cells, however, plant cells are interconnected by rigid cell walls, and their growth generates a considerable amount of tension. Local growth regulation between adjacent cells and tissues is essential for maintaining organ integrity, and in 1859 Wilhelm Hoffmeister proposed the "Theory of Tissue Tension," a theory that states that the tension between cells and tissues is a function of their interconnectedness, and that the tension between cells and tissues is a function of their interconnectedness. This theory suggested that the internal pressure of the plant body exerts tension stress on the epidermis. Although this proposal provoked lively debate in the 19th century, its validation has been mainly through artificial manipulation via phytohormones and other means. The results of these studies indirectly suggested that the internal pressure generated by the internal tissues of plants actually exerts itself on the outer epidermis. However, now, more than 160 years after the theory of tissue tension was proposed, we have succeeded in directly proving the "theory of tissue tension" for the first time using molecular developmental genetics and biomechanical methods, using a clv3 det3 mutant of Arabidopsis thaliana that "causes stem cracks," which we originally isolated. In terms of applications, it is expected to be used to create thicker columns in parquet construction, and has the potential to broaden the range of earthquake-resistant reinforcement techniques for all types of buildings in Japan, a country known for its major earthquakes.

The research results were published online in the international journal DEVELOPMENT on February 26, 2012 at 12:00 p.m. (GMT). It was also introduced in the "Research Highlight" section as a notable paper in the issue, and was featured on the cover of the issue.

Figure: (Top) Cracks on the stem of clv3 det3 double mutant. Photographs of plants one month after sowing. White arrowheads indicate cracks. Scale: 5 mm. (Bottom) Microscopic image of a transverse section of a clv3 det 3 double mutant stem after crack initiation. Scale: 500 µm.

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