Abstract:

Sugar beet （Beta vulgaris） is used as a pioneer crop for saline-alkali soil remediation in northern China. In this context， there is significant theoretical value in investigating crop genetic improvement through the identification of key salt-tolerance genes. Studies have shown that the betaine aldehyde dehydrogenase gene family BvBADHs may play a role in beet salt stress through facilitating glycine betaine biosynthetis. In this study， BvBADH2 was cloned from the salt-tolerant sugar beet cultivar ‘Gantang 7’ and BvBADH2-overexpressing Arabidopsis thaliana lines were generated by Agrobacterium-mediated transformation to systematically analyze and confirm its salt-tolerance mechanisms. Gene cloning and bioinformatics analysis showed that the full length of the BvBADH2 coding sequence （CDS） is 1512 bp， encoding 503 amino acids. The relative molecular weight of the predicted protein is 54.78 kDa， the isoelectric point is 5.37， and the instability index is 31.62. It contains a conserved aldehyde dehydrogenase domain （Aldedh， PF00171）， and the promoter region has a variety of abiotic stress-responsive cis-acting elements. In the salt-stress tolerant phenotype of transgenic A. thaliana under 150 mmol·L^-1 NaCl stress， the root length， fresh weight and chlorophyll content of the higher expression transgenic lines OE₁ and OE₃ were significantly increased by 129.1%， 125.0%， 104.8% and 137.5%， 126.3%， 107.2%， respectively， compared with the wild type （P<0.01）. Further studies revealed that BvBADHs overexpression of transgenic plants effectively maintained cell osmotic potential homeostasis by specifically accumulating osmotic protective substances such as glycine betaine， proline， and soluble sugar. Concurrently， dynamic activation of antioxidant enzyme systems-superoxide dismutase， peroxidase， and catalase-significantly reduced reactive oxygen species accumulation and alleviated membrane lipid peroxidation. These findings indicate that BvBADH2 confers salt tolerance through an “osmotic-antioxidant synergistic regulatory network”， marking the first functional validation of this gene’s conservation in model plants. This study provides critical insight for the development of enzymatic gene resources aimed at enhancing crop salt tolerance through molecular design breeding.

Key words: betaine aldehyde dehydrogenase, salt stress, osmotic adjustment, oxidative damage, antioxidant system