Harnessing MRI for imaging seeds of crops and model plants

Introduction: Depending on the research question, seeds can be analyzed at many different levels: from an overall morphology of the whole seed down to cellular level. Destructive assays are inappropriate if there is a need to grow material post analysis, and are especially undesirable in situations where the quantity of the seeds available is limited. Thus, non-invasiveness is an important further criterion in the context of functional seed analysis technologies.

Methods: We define three main foci in our work: (i) increasing resolution for structural imaging on small sized seeds; (ii) creating MRI methods to visualize the seed composition; (iii) developing imaging protocols to monitor the developmental processes in seeds, e.g. embryogenesis, storage processes and seed germination. A 7T as well as a 17.6T preclinical MRI system were used for imaging. Different RF resonators were utilized to achieve the best possible signal to noise ratio for each seed.,

Results and Discussion: High resolution 3D images of seeds/fruits were acquired and the feasibility of MRI for application on mono and dicotyledonous species which differ up to 100-fold in size [1] [2] was shown. Localization of sucrose and accumulation of amino acid (alanine) was observed in living grains of barley [3] [4] and open new perspective for using MRI in study on seed metabolism. MR imaging and modeling of developing embryos in oilseed rapeseeds, which was related to flux balance analysis and seed architecture shows its creative power in exploring the seed development [5] . Although, MRI represents a powerful tool in seed research, its low throughput, the complexity of the technology and its high costs hamper a more successful progress of MRI in seed science.
We conclude that the MR imaging tools open new perspectives for breeding and plant biology in general. In our opinion, the development of novel approaches in both hardware design as well as progress in developments of novel sequences (e.g. application of UTE) and improvements of data processing tools show promise in evaluating both structure and metabolism in space and time, in mature and developing plant seeds. Once, simplified protocols for routine work ("push-button applications") are available MRI might boost its acceptance and facilitate the screening of large seed collections by plant scientists.