As a flooding-tolerant tree species, Taxodium distichum has been utilized in afforestation projects and proven to have important value in flooding areas. Alcohol dehydrogenase (ADH), which participates in ethanol fermentation, is essential for tolerance to the anaerobic conditions caused by flooding. In a comprehensive analysis of the ADH gene family in T. distichum, TdADHs were cloned on the basis of whole-genome sequencing, and then bioinformatic analysis, subcellular localization, and gene expression level analysis under flooding were conducted. The results show that the putative protein sequences of 15 cloned genes contained seven TdADHs and eight TdADH-like genes (one Class III ADH included) that were divided into five clades. All the sequences had an ADH_N domain, and except for TdADH-likeE2, all the other genes had an ADH_zinc_N domain. Moreover, the TdADHs in clades A, B, C, and D had a similar motif composition. Additionally, the number of TdADH amino acids ranged from 277 to 403, with an average of 370.13. Subcellular localization showed that, except for TdADH-likeD3, which was not expressed in the nucleus, the other genes were predominantly expressed in both the nucleus and cytosol. TdADH-likeC2 was significantly upregulated in all three organs (roots, stems, and leaves), and TdADHA3 was also highly upregulated under 24 h flooding treatment; the two genes might play key roles in ethanol fermentation and flooding tolerance. These findings offer a comprehensive understanding of TdADHs and could provide a foundation for the molecular breeding of T. distichum and current research on the molecular mechanisms driving flooding tolerance.

MicroRNAs (miRNAs) are a type of noncoding RNA participating in the post-transcriptional regulation of gene expression that regulates plant responses to salt stress. Small RNA sequencing was performed in this study to discover the miRNAs responding to salt stress in Taxodium hybrid ‘Zhongshanshan 405’, which is tolerant to salinity stress. A total of 52 miRNAs were found to be differentially expressed. The target genes were enriched with gene ontology (GO), including protein phosphorylation, cellular response to stimulus, signal transduction, ATP and ADP binding, showing that miRNAs may play key roles in regulating the tolerance to salt stress in T. hybrid ‘Zhongshanshan 405’. Notably, a G-type lectin S-receptor-like serine/threonine-protein kinase (GsSRK) regulated by novel_77 and novel_2 miRNAs and a mitogen-activated protein kinase kinase kinase (MAPKKK) regulated by novel_41 miRNA were discovered under both short- and long-term salt treatments and can be selected for future research. This result provides new insights into the regulatory functions of miRNAs in the salt response of T. hybrid ‘Zhongshanshan 405’.