Identification and characterization of the DREB family in Chinese yam and functional study of DoDREB28 under drought stress

BACKGROUND: Dehydration responsive element-binding protein (DREB) serves as a core transcriptional regulator of abiotic stress responses, yet a systematic DREB gene locus map has not been established for Chinese yam (Dioscorea opposita). Given Chinese yam's dual role as a staple food crop and medicinal tuber, elucidating DREB gene function is of considerable importance. It remains unclear whether, and how, the Chinese yam DREB family coordinates responses to drought, high salinity, or low temperature. Therefore, a genome-wide survey of DREB members, coupled with functional validation of the key drought-tolerance regulator DoDREB28, may reveal the molecular framework underlying this food-medicine crop's adaptation to adverse environments. RESULTS: We identified 32 DoDREB members that clustered into six subgroups (A1-A6), a number markedly lower than that of Arabidopsis (56) and rice (57); the closely related species greater yam also harbors only 47 loci, indicating a contractive pattern of the family within Dioscorea. All paralogues retain an intact AP2 domain, and 84.62% of duplicate pairs originated from segmental duplication under strong purifying selection (Ka/Ks < 0.35), underscoring the functional conservation. Transcriptome profiling integrating drought, salt, and cold stress revealed that the DoDREB family exhibits distinct expression patterns. Specifically, DoDREB28 showed sustained upregulation within 24 h under 20% (w/v) PEG-simulated drought stress, whereas its expression remained suppressed throughout 24 h of 200 mM NaCl salt stress. Overexpression of DoDREB28 in Arabidopsis enhanced primary-root elongation, proline content, and SOD activity, while reducing MDA and H₂O₂ accumulation under 300 mM mannitol, confirming that improved osmotic adjustment and antioxidant capacity confer greater drought tolerance. Population-genomic analysis of 101 landraces uncovered two haplotypes: Haplotype 1 (Hap1) displayed significantly higher drought-induced expression than Haplotype 2 (Hap2), which predominates in humid regions (Shandong and Hunan provinces, China), implying relaxed selection during domestication. CONCLUSIONS: Our study systematically analyzed the Chinese yam DREB family based on the current dataset, revealing that DoDREB28 exhibits significant upregulation in drought-stressed transcriptomes. It can be tentatively classified as a candidate positive regulator involved in drought response. This gene and its variant sites serve only as preliminary molecular marker resources.