Cold damage is a major challenge in rice production, and identifying key gene modules in signaling pathways is a crucial means of addressing this issue. A Chinese research team has recently discovered a part of the plant's cell membrane that helps plants sense when it's cold.

This cell membrane component, known as the COLD6-OSM1 module, triggers the production of a special molecule, 2',3'-cAMP, which helps plants sense and respond to low temperatures. This secondary messenger is a key upstream component that mediates the signaling pathway by directly responding to signals from cold sensors.

Previous studies have found that cold sensors predominantly trigger a calcium ion (Ca²⁺) signaling pathway that acts as a secondary messenger, but few other molecules functioning as secondary messengers had been identified.

Japonica rice and indica rice are two subspecies that vary in chilling tolerance. In this study, Prof. CHONG Kang's team from the Institute of Botany of the Chinese Academy of Sciences used a genetic population derived from a cross between the chilling-tolerant japonica variety Kongyu131 and the chilling-sensitive indica variety Zhefu802 to identify a major QTL gene, COLD6 (CHILLING TOLERANCE DIVERGENCE 6), which negatively regulates cold tolerance in rice.

The team found a difference between japonica and indica rice in the number of CTC codons (encoding leucine) in the coding region of the COLD6 alleles. Specifically, japonica rice showed lower accumulation of the COLD6 protein from the plasma membrane under low-temperature conditions, thereby conferring stronger cold tolerance.

Further experiments indicated that COLD6 interacted with the cold-induced plasma membrane protein OSM1 to form a complex for sensing low temperatures. This interaction led to increased 2',3'-cAMP production, which complements calcium signaling to enhance cold tolerance in rice.

Since most modern "three-line" hybrid rice parents carry the tolerant COLD6 allele, editing the COLD6 gene may improve cold tolerance across various rice cultivars without negative effects on agronomic traits. These findings may be used to develop new strategies for breeding cold-resistant rice varieties.

Results of this study were published in Molecular Cell on Oct. 31.

The COLD6-Osm1 module, located at the plasma membrane, converts chilling signals into 2',3'-camp within the cell to help it defend against cold stress. (Image by YOU Yanping)