2021 Annual report of Yushan scholarship Dr. Wilhelm Gruissem
Introduction to the event
Dr. Gruissem use plant genetic engineering to improving the nutritional quality of rice endosperm and cassava storage root and starch yield to fight hidden hunger and food crisis.
Professor Gruissem planted biofortified rice in National Chung Hsing University experimental agriculture station for agronomic evaluation. The rice research team of the National Chung Hsing University collaborated with the "Higher Education SPROUT Project (The featured areas research center program)". Based on the Taiwan Rice Insertional Mutant (TRIM) collection library already owned by our school and the "T-DNA rice mutant original library" transferred from the Academia Sinica to our school, combined with the "International Rice Genome Research Center" jointly established by our school and the Academia Sinica and our school " "Agricultural Biotechnology Research Center" and "NCHU-UCD International Plant and Food Biotechnology Center" jointly established the "Advanced Plant Biotechnology Center".
Projections of the United Nations show that the world population will grow to more than 9 billion people by 2050. To provide sufficient and nutritious food for healthy diets requires an increase in yield and micronutrient improvement of staple crops. Major crops such as maize, wheat, rice, cassava and potatoes are rich in starch and together they provide more than 85% of the carbohydrate calories consumed worldwide. People for whom these crops are the primary staple food receive enough calories but they are often malnourished because the seeds, tubers and roots of these plants do not contain enough of the necessary vitamins and minerals such as iron for a healthy diet. For example, 1.6 billion people worldwide suffer reduced productive capacity due to iron-deficiency anemia (Bhullar and Gruissem, 2013; Vasconcelos et al, 2016). Achieving higher micronutrient and starch content for health and nutrition is often not possible with available breeding germplasm, especially in rice and clonally propagated crops such as cassava. Together with other experts, Dr. Gruissem recently made the case for crop biofortification in a perspective article published in Nature Communications (Van Der Straeten, Bhullar, De Steur, Gruissem et al. 2020, https://www2.nchu.edu.tw/en-news-detail/id/321/title/Plant_genetic_engineering_to_fight_hidden_hunger). Based on his extensive knowledge from basic research on Arabidopsis and other plants, Dr. Gruissem employs gene technology and CRISPR-Cas9 strategies to increase micronutrient and vitamin content of rice and cassava, modify starch quality in cassava, and increase cassava storage root yield.
In rice, Dr. Gruissem and his team have developed different strategies to increase iron and zinc in the endosperm of rice grains (polished rice). Rice is one of the most consumed staple foods but contains
insufficient essential micronutrients for daily dietary intake. Breeding rice with high micronutrient content is not possible because of unavailable germplasm and negative linkage with yield. His strategy for iron and zinc biofortification of rice is to facilitate root uptake efficiency, translocation within the plant, and the storage of iron in the endosperm. In 2019 and 2020, Dr. Gruissem and his teams investigated the agronomic performance of the genetically micronutrient-improved rice lines in field experiments using phenotyping and molecular analyses. In three field experiments they tested rice lines with increased iron and zinc in the endosperm that were previously. The field trial data show that the micronutrient-improved rice lines maintained their high iron and increased zinc content in the polished grains, indicating that the genetically engineered trait is stable.
In addition to collaborating with Taiwan experts and scholars, Professor Gruissem also promotes international academic research cooperation and exchanges. Professor Gruissem leads the research team of National Chung Hsing University to participate in international research projects and cooperate with foreign universities or research institute. The Cassava Source-Sink (CASS) project aims to develop robust and yield-improved cassava varieties that will be provided to small farmers in Africa to improve food security in sub-Saharan Africa. Its team members are distributed all over the world, including Switzerland, Germany, the United Kingdom, and Nigeria. At the same time, the Gruissen Professor ETH Zurich and the National Chung Hsing University research team worked together to improve the nitrogen use efficiency of cassava to increase the nitrogen use efficiency of crops and reduce the application of chemical fertilizers.
Cassava (Manihot esculenta Crantz) is an important crop in tropical and subtropical countries (FAOSTAT, 2016;http://www.fao.org/faostat/en/#search/Cassava%20and%20products). Until the 1970’s, Taiwan had a significant commercial cassava production for food and starch extraction. Today production is only 11,000 tons annually, and cassava starch is mainly used in tapioca pearls for bubble tea. In other parts of the world, and especially Sub-Saharan Africa, cassava is an important staple crop for several hundred million people. But compared to other staple crops such as maize and wheat, cassava has received little scientific attention until recently. The Cassava Source-Sink (CASS) research project aims at increasing cassava storage root and starch yield by improving the sink (photosynthesis, phloem loading) and source (sucrose to starch conversion) metabolism.
To simultaneously improve leaf photosynthesis, phloem transport, storage root development and starch biosynthesis, the CASS team focuses on engineering metabolic and physiological processes by designing and transforming multigene constructs into cassava. To validate the engineering concept, Dr. Gruissem’s team at NCHU is evaluating the agronomic performance of the transgenic lines in confined field trials (CFT) at the NCHU Experimental Station, which has a subtropical climate suitable for cassava growth and no reports of major cassava diseases. Each experiment takes about three years from the design of the multigene constructs to the harvest of the transgenic lines and their subsequent biochemical and molecular analysis. The multigene constructs are first transformed into the farmer-preferred cassava varieties 60444 and TME7 using a high-throughput transformation pipeline established at ETH Zurich. After regeneration and selection of transgenic plantlets, they are prepared for agronomic performance testing. The experiment starts with the multiplication of plantlets of the transgenic cassava lines at ETH Zurich. The sterile cassava tissue culture plantlets are then shipped to the NCHU Experiment Station (with the appropriate import permits), where they are transferred to soil and grown in the greenhouse for 8 weeks. The potted plants are then planted in the field for the growth season (March to November). During the growth season, an unmanned aerial vehicle (UAV) records plant height and canopy volume from which the growth rate can be determined. This provides information for the seasonal dynamics of early cassava growth and development. Depending on the constructs, leaf samples are also collected during the growth season for biochemical and molecular analyses. After 8 months in the field, the wild-type cassava variety 60444 and transgenic lines can grow up to 3.5 m in height and produce 10 kg of root fresh weight or more (see photograph of Dr. Gruissem in front of a 60444 plant). The first CFT in 2019 tested 89 independent genetic events, and events with the most promising agronomic performance were selected for a CFT at the International Institute for Tropical Agriculture (IITA) in Nigeria in 2020. The phenotype data from the field trial are combined with biochemical data from the laboratory and predictions from genome-scale metabolic modeling to inform and refine the genetic engineering strategy.
figure 1: Overview of different micronutrient improvement strategies of rice endosperm. Iron and zinc biofortification rice in NCHU agriculture experimental station.
figure 2:Overview of the CASS strategy for improving source-sink relations with multigene constructs to improve leaf photosynthesis, facilitate sucrose transport to roots, and increase starch production in storage roots.
(Dr. Gruissem in front of his cassava plants in the field)