1. RIKEN Plant Science Center, Tsurumi, Yokohama 230-0045, Japan
2. Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuencho, Naka-ku, Sakai, Osaka 599-8531, Japan
3. Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi, Bunkyo, Tokyo 113-8652, Japan
4. Weed Science Center, Utsunomiya University, Utsunomiya 321-8505, Japan

Correspondence to: Shinjiro Yamaguchi¹ Correspondence and requests for materials should be addressed to Sh.Y. (Email: shinjiro@postman.riken.jp).

Abstract

Shoot branching is a major determinant of plant architecture and is highly regulated by endogenous and environmental cues. Two classes of hormones, auxin and cytokinin, have long been known to have an important involvement in controlling shoot branching. Previous studies using a series of mutants with enhanced shoot branching suggested the existence of a third class of hormone(s) that is derived from carotenoids, but its chemical identity has been unknown. Here we show that levels of strigolactones, a group of terpenoid lactones, are significantly reduced in some of the branching mutants. Furthermore, application of strigolactones inhibits shoot branching in these mutants. Strigolactones were previously found in root exudates acting as communication chemicals with parasitic weeds and symbiotic arbuscular mycorrhizal fungi. Thus, we propose that strigolactones act as a new hormone class—or their biosynthetic precursors—in regulating above-ground plant architecture, and also have a function in underground communication with other neighbouring organisms.

1. RIKEN Plant Science Center, Tsurumi, Yokohama 230-0045, Japan
2. Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuencho, Naka-ku, Sakai, Osaka 599-8531, Japan
3. Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi, Bunkyo, Tokyo 113-8652, Japan
4. Weed Science Center, Utsunomiya University, Utsunomiya 321-8505, Japan

Correspondence to: Shinjiro Yamaguchi¹ Correspondence and requests for materials should be addressed to Sh.Y. (Email: shinjiro@postman.riken.jp).

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