Fruit shape diversity in the Brassicaceae is generated by varying patterns of anisotropy.

Tilly Eldridge,Łukasz Łangowski,Laila Moubayidin,Richard Kennaway,Nicola Stacey,Adrien Sicard,Enrico S Coen,Paul Southam,Michael Lenhard,Friederike Jantzen,Lars Østergaard

doi:10.1242/dev.135327

Abstract

Fruits exhibit a vast array of different 3D shapes, from simple spheres and cylinders to more complex curved forms; however, the mechanism by which growth is oriented and coordinated to generate this diversity of forms is unclear. Here, we compare the growth patterns and orientations for two very different fruit shapes in the Brassicaceae: the heart-shaped Capsella rubella silicle and the near-cylindrical Arabidopsis thaliana silique. We show, through a combination of clonal and morphological analyses, that the different shapes involve different patterns of anisotropic growth during three phases. These experimental data can be accounted for by a tissue-level model in which specified growth rates vary in space and time and are oriented by a proximodistal polarity field. The resulting tissue conflicts lead to deformation of the tissue as it grows. The model allows us to identify tissue-specific and temporally specific activities required to obtain the individual shapes. One such activity may be provided by the valve-identity gene FRUITFULL, which we show through comparative mutant analysis to modulate fruit shape during post-fertilisation growth of both species. Simple modulations of the model presented here can also broadly account for the variety of shapes in other Brassicaceae species, thus providing a simplified framework for fruit development and shape diversity.

Highlights

Despite the great diversity in plant organ shapes, it has been proposed that common principles may underlie shape determination
From 0-2 days after initiation (DAI) defines an initial phase of high growth rate preferentially along the longitudinal axis of the gynoecium in both Capsella and Arabidopsis (Table 1)
After this early phase of anisotropic growth, there is a drop in both growth rate in length and anisotropy in Capsella (Table 1, Fig. 1B,C), whereas in Arabidopsis anisotropy is maintained while growth rate in length is less reduced (Table 1, Fig. 1B,D)

Summary

Introduction

Despite the great diversity in plant organ shapes, it has been proposed that common principles may underlie shape determination (reviewed by Sluis and Hake, 2015). Key genetic factors involved in determining fruit shape in. Conflicts generated by regions growing with different rates or orientations lead to changes in curvature and shape. It is unclear whether such models could account for the growth patterns and diversity of 3D fruit shapes.

Methods

Results

Conclusion