http://english.cas.cn/newsroom/research_news/life/202412/t20241211_894322.shtml
A recent study by Prof. XU Cao’s team from the CAS Institute of Genetics and Developmental Biology (IGDB) addresses global food security under the aspect of “climate-smart” crops that achieve higher yields under normal conditions and stable yields under heat stress.
To this end, the “source-sink” relationship in plants must be considered. Source tissues (e.g., leaves) are net producers of photoassimilates—i.e., primarily carbohydrates such as sucrose. In contrast, sink tissues (e.g., fruits, seeds, roots, developing flowers, cotton fibers, and storage organs) are net importers, which use or store photoassimilates. The cell wall invertase gene (CWIN) is the crucial gene regulating the source-sink relationship. The enzyme encoded by this gene unloads and converts sucrose transported from leaves into glucose and fructose within sink organs, where these sugars can be directly absorbed and utilized. These sugars are not only essential nutrients for the development of fruits and seeds, but significantly influence the sweetness of fruits and the quality of rice grains. Heat stress represses CWIN activity and thus disrupts the source-sink balance, resulting in inadequate energy supply in sink organs, reduced reproductive development, and yield penalties.
IProf. XU Cao and his team developed a strategy based on climate-responsive optimization of carbon partitioning to sinks (CROCS) by rationally manipulating the expression of CWIN genes in fruit and cereal crops. They precisely knocked-in a 10-bp heat-shock element (HSE) into promoters of CWIN genes in elite rice and tomato cultivars, using self-developed high-efficiency, prime-editing tools. HSE insertion endows CWINs with heat-responsive upregulation in both controlled and field environments to enhance carbon partitioning to rice grains and tomato fruits. Multi-location and multi-season yield tests on tomatoes under various cultivation conditions including greenhouses and open fields showed that under normal conditions, the CROCS strategy increased tomato yields by 14% to 47%. Under heat stress, it increased per-plot fruit yield by 26%~33% over controls and rescued 56.4%~100% of fruit yield losses caused by heat stress. Notably, aspects of fruit quality such as uniformity and sugar content were significantly improved compared to unmodified controls.
In addition, rice cultivars improved by this strategy not only showed a yield increase of 7% to 13% under normal conditions, but also showed a 25% grain yield increase over controls under heat-stress conditions. Specifically, up to 41% of heat-induced grain losses were rescued in rice.
CROCS is an efficient, versatile, prime-editing based system for rapid crop improvement, which paves the way to rapidly create climate-smart crops by targeted insertion of environment-responsive cis-regulatory elements. The strategy also provides effective gene-editing tools and feasible operational procedures for the fundamental study of plant responses to stress and can also been applied to crops such as soybeans, wheat, and corn.
