Using Arabidopsis to Study Shoot Branching in Biomass Willow

Sally P Ward,Jemma Salmon,Ottoline Leyser,Angela Karp,Steven J Hanley

doi:10.1104/pp.113.218461

Sally P Ward, Jemma Salmon + Show 3 more

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https://doi.org/10.1104/pp.113.218461

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Abstract

The success of the short-rotation coppice system in biomass willow (Salix spp.) relies on the activity of the shoot-producing meristems found on the coppice stool. However, the regulation of the activity of these meristems is poorly understood. In contrast, our knowledge of the mechanisms behind axillary meristem regulation in Arabidopsis (Arabidopsis thaliana) has grown rapidly in the past few years through the exploitation of integrated physiological, genetic, and molecular assays. Here, we demonstrate that these assays can be directly transferred to study the control of bud activation in biomass willow and to assess similarities with the known hormone regulatory system in Arabidopsis. Bud hormone response was found to be qualitatively remarkably similar in Salix spp. and Arabidopsis. These similarities led us to test whether Arabidopsis hormone mutants could be used to assess allelic variation in the cognate Salix spp. hormone genes. Allelic differences in Salix spp. strigolactone genes were observed using this approach. These results demonstrate that both knowledge and assays from Arabidopsis axillary meristem biology can be successfully applied to Salix spp. and can increase our understanding of a fundamental aspect of short-rotation coppice biomass production, allowing more targeted breeding.

Highlights

The success of the short-rotation coppice system in biomass willow (Salix spp.) relies on the activity of the shoot-producing meristems found on the coppice stool
To assess whether the same is true for Salix spp., nodal segments were excised from the secondary branches produced when stem cuttings from fieldgrown plants were sprouted in water
On these freshly sprouted secondary branches, the axillary meristems remained dormant indefinitely unless the apex was removed, which resulted in activation of the axillary meristems in an apical-basal gradient similar to that observed in Arabidopsis (Hempel and Feldmann, 1994; Grbic and Bleecker, 1996)

Summary

Introduction

The success of the short-rotation coppice system in biomass willow (Salix spp.) relies on the activity of the shoot-producing meristems found on the coppice stool. The mechanisms underlying axillary bud activation in Arabidopsis (Arabidopsis thaliana) have been investigated in some detail over the past few years, resulting in the identification of a network of interacting plant hormones that move systemically through the plant to control bud growth (Leyser, 2009). Central to this network is auxin, synthesized in the growing shoot apex and transported basipetally in the polar auxin transport stream (PATS), from where it acts indirectly to inhibit bud growth (Thimann and Skoog, 1933; Morris, 1977; Booker et al, 2003). This process strongly correlates with bud activation (Morris, 1977; Li and Bangerth, 1999; Prusinkiewicz et al, 2009; Balla et al, 2011)

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