Researchers from the Wuhan Botanical Garden of the Chinese Academy of Sciences have discovered the genetic secret behind bermudagrass's remarkable ability to thrive in salty soils, potentially paving the way for breeding more salt-tolerant crops. They identified a sophisticated salt-tolerance signaling pathway that enables bermudagrass to "pump out" excess salt, a major threat to food production globally.

Their findings were published in The Plant Cell on February 26.

Soil salinity is a growing global crisis that significantly impacts food production. Although bermudagrass (Cynodon dactylon) is renowned for its resilience to salt stress, the genetic basis of its salt tolerance has been unclear, hindering its use in saline soils.

The researchers 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.

The 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 and 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 and ultimately repress the CdSOS1 expression.

The breakthrough occurred when researchers identified 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 elucidates the molecular mechanisms underlying the variation in salt tolerance among bermudagrass's resilience and offers applications in agriculture. Identifying and deploying favorable FBX1 haplotypes such as CdFBX1.2 could accelerate molecular breeding efforts and help maintain 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, and the National Science Foundation for Distinguished Young Scholars of Hubei Province, and others.