Researchers at the Wuhan Botanical Garden of the Chinese Academy of Sciences have unlocked a genetic secret behind bermudagrass's remarkable ability to thrive in salty soils, potentially paving the way for breeding more salt-tolerant crops. They have identified a sophisticated salt-tolerance signaling pathway that allows the bermudagrass to 'pump out' excess salt, a major threat to food production globally. The findings were recently published in The Plant Cell.

Soil salinity is a growing global crisis, significantly impacting food production. While bermudagrass (Cynodon dactylon) is known for its exceptional resilience to salt stress, the precise genetic basis for salt tolerance has remained poorly understood, hindering its utilization in saline soils.

The research team pinpointed a sophisticated molecular pathway (the CdFBX1-CdMYB26-CdMYB5-CdSOS1 regulatory module) that orchestrates salt tolerance. Central to this pathway is the Salt Overly Sensitive 1 (SOS1) Na⁺/H⁺ antiporter, a critical 'salt extrusion pump' that actively expels excessive sodium ions (Na⁺) from plant cells to maintain internal balance during salt stress.

Researchers discovered that a transcription factor, CdMYB5, acts as a positive regulator by directly binding to and activating the expression of the CdSOS1 (a major gene underlying salt tolerance in Bermudagrass) to promote Na⁺ efflux to enhance salt tolerance. However, another transcription factor, CdMYB26, acts as a repressor. It functions as a negative regulator by directly binding to the promoter of CdMYB5 to repress its expression, thus ultimately repress the CdSOS1 expression.

The breakthrough came with the identification of a natural variant of an E3 ubiquitin ligase, named CdFBX1 (CdFBX1.1 and CdFBX1.2). The superior CdFBX1.2 variant acts quickly by interacting with the 'repressor' protein CdMYB26, promoting its ubiquitination and subsequent degradation in the 26S proteasome. This critical action relieves the repression on CdMYB5, allowing the downstream SOS1 'salt pump' and effectively maintain ion homeostasis.

This discovery not only elucidates the molecular mechanisms underlying the variation in salt tolerance among bermudagrass's resilience, but also offers applications for agriculture. Identifying and deploying favorable FBX1 haplotypes like CdFBX1.2 could accelerate molecular breeding efforts helping to maintaining yield and turf quality as soil salinization worsens.

This work was supported by the National Natural Science Foundation of China, the Major Science and Technology Innovation Project of Shandong Province, the National Science Foundation for Distinguished Young Scholars of Hubei Province, the International Science and Technology Cooperation Project of Hubei Province, the Strategic Priority Research Program of the Chinese Academy of Sciences, the Science & Technology Specific Projects in Agricultural High‐tech Industrial Demonstration Area of the Yellow River Delta and the Hunan Provincial Key Research and Development Program.