Towards deepening of multi-omics integrated approach in root system to develop climate-resilient rice

Root is the only organ to uptake water and nutrients from soil. Root system is crucial for plants to survive and/or adapt to environmental stresses, therefore, root system architecture (RSA) is an important breeding target for developing climate-resilient rice. Since the rice genome has been completely sequenced, many genes for root development were cloned and characterized so far. In addition, with the advances in technologies related to omics analysis such as high-throughput sequencer, transcriptome analysis of roots has also been progressed. In contrast, high-throughput root phenotyping has not been established in not only rice but also whole plants because root is hidden underground. This should be a bottleneck for utilizing multi-omics integrated approach for molecular breeding of RSA. We first summarize previous transcriptome analysis for root development under various abiotic stresses such as drought, salinity, heat etc. and overview current status of root phenotyping technology and modelling in rice. These knowledges would allow us to contemplate a possibility of applying of integrated multi-omics data of RSA to molecular breeding of climate-resilient rice

Plant root PET: visualization of photosynthate translocation to roots in rice plant

Roots are essential to plants for uptake of water and nutrients. For the improvement of crop production, it is necessary to understand the elucidation of the root development and its function under the ground. Espeially, photosynthate translocation from plant leaves to roots is an important physiological function that affects the root elongation, adaptation to the soil environment and nutrients uptake. To evaluate the translocation dynamics to roots, positron emission tomography (PET) and 11C tracer have been used. However, the spatial resolution is degraded at roots that develop around the peripheral area of field of view (FOV) due to parallax errors. In this study, to overcome this problem, we developed a small OpenPET prototype applying four-layer depth-of-interaction detectors. We demonstrated the imaging capability of 11C-photosynthate translocation to rice roots that develop throughout the entire PET field. We also tried to obtain structural information of roots by high-throughput X-ray computed tomography (CT) system using the same test plant. As a result, we succeeded in visualizing the root structure that developed around the peripheral region of FOV and imaging the accumulation of 11C-photosynthate to the roots in those areas without degrading the spatial resolution. From obtained images, we also succeeded in evaluating the translocation dynamics varied by roots. The combined use of the high-throughput CT system and the OpenPET prototype was demonstrated to be appropriate for structural and functional analysis of roots