Pyridine-type alkaloid composition affects bacterial community composition of floral nectar.

Yana Aizenberg-Gershtein,Ian T Baldwin,Rakesh Santhanam,Malka Halpern,Ido Izhaki,Pavan Kumar

doi:10.1038/srep11536

Yana Aizenberg-Gershtein, Ian T Baldwin + Show 4 more

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https://doi.org/10.1038/srep11536

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Abstract

Pyridine-type alkaloids are most common in Nicotiana species. To study the effect of alkaloid composition on bacterial community composition in floral nectar, we compared the nicotine-rich wild type (WT) N. attenuata, the nicotine biosynthesis-silenced N. attenuata that was rich in anatabine and the anabasine-rich WT N. glauca plants. We found that the composition of these secondary metabolites in the floral nectar drastically affected the bacterial community richness, diversity and composition. Significant differences were found between the bacterial community compositions in the nectar of the three plants with a much greater species richness and diversity in the nectar from the transgenic plant. The highest community composition similarity index was detected between the two wild type plants. The different microbiome composition and diversity, caused by the different pyridine-type alkaloid composition, could modify the nutritional content of the nectar and consequently, may contribute to the change in the nectar consumption and visitation. These may indirectly have an effect on plant fitness.

Highlights

For why plants produce secondary metabolites in nectar relates to the possible role that these metabolites play in shaping the bacterial community composition in nectar, which, in turn, may have an indirect effect on the attraction or deterrence of plant visitors
We were able to demonstrate that the elimination of a single metabolite - nicotine, which resulted in anatabine accumulation, altered the bacterial communities in the floral nectar of N. attenuata and that the bacterial community in the outliner species (N. glauca) was more similar to that of N. attenuata wild type (WT) than to the irPMT plants
We have demonstrated that the elimination of a single secondary metabolite - nicotine, which caused an elevation of another secondary metabolite - anatabine, drastically affected the composition and diversity of bacterial communities in floral nectar

Summary

Introduction

For why plants produce secondary metabolites in nectar relates to the possible role that these metabolites play in shaping the bacterial community composition in nectar, which, in turn, may have an indirect effect on the attraction or deterrence of plant visitors. Steppuhn et al.[27] transformed native N. attenuata to down-regulate nicotine expression, by silencing putrescine-N-methyl transferase (to produce irPMT plants), and demonstrated that nicotine protects the plant from herbivores. They found that anatabine (another pyridine-alkaloid), was undetectable in the WT plants, while in the irPMT plants its concentrations increased. The aim of the current study was to examine whether the pyridine-alkaloid composition in the floral nectar affects the bacterial community composition in nectar To achieve this goal, we first compared the bacterial community composition in the nectar of irPMT N. attenuata plants (with silenced nicotine expression) with that in the nectar of N. attenuata WT plants. We were able to demonstrate that the elimination of a single metabolite - nicotine, which resulted in anatabine accumulation, altered the bacterial communities in the floral nectar of N. attenuata and that the bacterial community in the outliner species (N. glauca) was more similar to that of N. attenuata WT than to the irPMT plants

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