Scientists from Thailand Use Promoter Editing to Boost Rice Water Efficiency

Scientists at Chulalongkorn University and their collaborators have developed a way to make rice crops more drought-resilient by editing the promoter of a key gene that is controls leaf spore formation. By using a tRNA-based CRISPR-Cas9 system to alter the regulatory promoter region of OsGTL1, the team successfully reduced the expression of this master controller of stomatal development. While completely knocking out OsGTL1 causes seed sterility, modifying its upstream promoter instead allowed researchers to modulate the gene's activity without harming plant fertility.

To see how these genetic edits affected the leaf structure, the researchers examined how stomata formed in the edited plants. Lowering OsGTL1 expression in developing leaves led to a clear drop in overall stomatal density. Microscopic imaging showed that while early cell division began normally, some guard mother cells failed to complete their final symmetric division, preventing them from maturing into functional pore pairs. Inheritance tests also proved that this reduced stomatal trait is passed down as a recessive allele.

Physiological tests revealed that plants with fewer stomata maintained normal photosynthetic rates while losing far less water through transpiration. This change boosted instantaneous water use efficiency by 14% to 15% during the tillering stage and protected water retention under reproductive-stage drought. Although the edited lines produced slightly lower yields under normal conditions, they suffered significantly smaller yield losses than wild-type rice when exposed to drought during the booting stage. By demonstrating how promoter editing can modulate gene expression without causing sterility, this approach could be leveraged in future studies to optimize the balance between water conservation and yield in climate-ready crops.

To learn more, read the full study in Plant Cell Reports.