Abstract
While often thought of as a smoking drug, tobacco (Nicotiana spp.) is now considered as a plant of choice for molecular farming and biofuel production. Here, we describe a noninvasive means of deriving both the distribution of lipid and the microtopology of the submillimeter tobacco seed, founded on nuclear magnetic resonance (NMR) technology. Our platform enables counting of seeds inside the intact tobacco capsule to measure seed sizes, to model the seed interior in three dimensions, to quantify the lipid content, and to visualize lipid gradients. Hundreds of seeds can be simultaneously imaged at an isotropic resolution of 25 µm, sufficient to assess each individual seed. The relative contributions of the embryo and the endosperm to both seed size and total lipid content could be assessed. The extension of the platform to a range of wild and cultivated Nicotiana species demonstrated certain evolutionary trends in both seed topology and pattern of lipid storage. The NMR analysis of transgenic tobacco plants with seed-specific ectopic expression of the plastidial phosphoenolpyruvate/phosphate translocator, displayed a trade off between seed size and oil concentration. The NMR-based assay of seed lipid content and topology has a number of potential applications, in particular providing a means to test and optimize transgenic strategies aimed at the manipulation of seed size, seed number, and lipid content in tobacco and other species with submillimeter seeds.
Highlights
While often thought of as a smoking drug, tobacco (Nicotiana spp.) is considered as a plant of choice for molecular farming and biofuel production
We describe a noninvasive means of deriving both the distribution of lipid and the microtopology of the submillimeter tobacco seed, founded on nuclear magnetic resonance (NMR) technology
The NMR-based assay of seed lipid content and topology has a number of potential applications, in particular providing a means to test and optimize transgenic strategies aimed at the manipulation of seed size, seed number, and lipid content in tobacco and other species with submillimeter seeds
Summary
To assess the diversity of lipid content within the seed of Nicotiana species, a set of 64 accessions held at the German Federal ex situ GenBank at Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung was surveyed. Our NMR platform allows to image the intact capsule three dimensionally and to obtain a count of the seed This was made possible by employing spin-echo imaging based solely on global chemical shift selective pulses. The indication from the NMR-based, three-dimensional reconstructions was that for all three species the volume of the embryo was less than that of the endosperm (Fig. 6, D–F). The ratio between these two volumes was 6.2 in N. tabacum but much higher in N. sylvestris (14.4) and N. tomentosiformis (22.7). An equivalent correlation was not obvious among the wild-type seeds (Fig. 7F)
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