Identification of CAMTA transcription factors and functional analysis of OsCAMTA4 in rice blast and salt stress

The OsCAMTA4 gene regulates salt and blast resistance in rice without yield loss via calcium and ABA signaling. As a key regulatory hub in the calcium signaling pathway, calmodulin-binding transcription activator (CAMTA) responds to diverse stresses and developmental signals. However, its roles in rice salt and rice blast stress responses remain largely unclear. Here, we characterized the rice CAMTA family genome-wide. Using the 3 K Rice Pan-genome and 3,000 Rice Functional Gene Haplotype Databases, we found seven core CAMTA genes are prevalent across 2,978 accessions but unevenly distributed among subgroups, with their three high-frequency haplotypes exerting distinct regulatory effects on key agronomic traits. The seven OsCAMTA genes show spatiotemporally specific responses to drought and cold stress. RT-qPCR revealed that OsCAMTA4 expression specifically was downregulated under rice blast but upregulated under salt stress. Overexpression of OsCAMTA4 enhanced salt tolerance by increasing seed germination rate, root length, proline content, and transcript levels of ABA signaling pathway genes, while decreasing malondialdehyde and hydrogen peroxide (H₂O₂) contents. Additionally, OsCAMTA4 knockout improved rice blast resistance by increasing proline and H₂O₂ accumulation and expression of disease resistance-related genes. The OsCAMTA4 protein is localized in the nucleus and interacts with OsCML2, suggesting it mediates stress responses via calcium ion (Ca²⁺) signaling. Notably, the actual presence of the OsCAMTA4 gene has no significant effect on rice yield over wild type, supporting its potential for improving salt tolerance and disease resistance without yield loss. Thus, it provides a new target for breeding broad-spectrum stress-resistant rice.