EgrDREB3 from Eucalyptus grandis confer Arabidopsis resilience to low temperature and salinity and senescence delay without growth penalty

EgrDREB3 (Eucgr.A02817), an A4-type DREB transcription factor from Eucalyptus grandis, which is strongly induced by cold, drought, and salinity stresses. When overexpressed in Arabidopsis. thaliana, EgrDREB3 markedly improved tolerance to both low temperature and salinity. The transgenic lines exhibited delayed senescence, improved leaf photosynthetic efficiency, increased biomass accumulation, and higher seed yield compared with wild type plants, accompanied by several days delay in bolting but promoting vegetative growth. Additionally, the elevated accumulation of both soluble sugars and free proline in transgenic lines suggests a potential role in stress mitigation. Transcriptome analysis revealed strong upregulation of several key stress-responsive genes, including COR47, GOLS3, RD29A, and RD29B. Concurrently, jasmonic acid (JA) levels were reduced in transgenic plants, along with increased expression of SOT14 and SOT15 which are involved in JA inactivation. This led to downregulation of MYC2 and its downstream senescence-associated target genes, such as NAP, NAC047, NAC019, and RD26. Furthermore, the suppression of both JA-dependent and JA-independent senescence pathways suggests a dual mechanism by which EgrDREB3 delays aging while enhancing stress tolerance. These findings identify EgrDREB3 as a promising molecular target for boosting abiotic stress resilience in Eucalyptus and other crop species, without sacrificing growth and yield potential.