The Taxodium hybrid ‘Zhongshanshan 406’ (T. hybrid ‘Zhongshanshan 406’) [Taxodium mucronatum Tenore × Taxodium distichum (L.). Rich] has an outstanding advantage in flooding tolerance and thus has been widely used in wetland afforestation in China. Alcohol dehydrogenase genes (ADHs) played key roles in ethanol metabolism to maintain energy supply for plants in low-oxygen conditions. Two ADH genes were isolated and characterized—ThADH1 and ThADH4 (GenBank ID: AWL83216 and AWL83217—basing on the transcriptome data of T. hybrid ‘Zhongshanshan 406’ grown under waterlogging stress. Then the functions of these two genes were investigated through transient expression and overexpression. The results showed that the ThADH1 and ThADH4 proteins both fall under ADH III subfamily. ThADH1 was localized in the cytoplasm and nucleus, whereas ThADH4 was only localized in the cytoplasm. The expression of the two genes was stimulated by waterlogging and the expression level in roots was significantly higher than those in stems and leaves. The respective overexpression of ThADH1 and ThADH4 in Populus caused the opposite phenotype, while waterlogging tolerance of the two transgenic Populus significantly improved. Collectively, these results indicated that genes ThADH1 and ThADH4 were involved in the tolerance and adaptation to anaerobic conditions in T. hybrid ‘Zhongshanshan 406’.

NAC transcription factor is one of the largest plant gene families, participating in the regulation of plant biological and abiotic stresses. In this study, 182 NAC proteins (HhNACs) were identified based on genomic datasets of Hibiscus hamabo Sieb. et Zucc (H. hamabo). These proteins were divided into 19 subfamilies based on their phylogenetic relationship, motif pattern, and gene structure analysis. Expression analysis with RNA-seq revealed that most HhNACs were expressed in response to drought and salt stress. Research of quantitative real-time PCR analysis of nine selected HhNACs supported the transcriptome data’s dependability and suggested that HhNAC54 was significantly upregulated under multiple abiotic stresses. Overexpression of HhNAC54 in Arabidopsis thaliana (A. thaliana) significantly increased its tolerance to salt. This study provides a basis for a comprehensive analysis of NAC transcription factor and insight into the abiotic stress response mechanism in H. hamabo.

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.

As a pivotal wetland tree, Taxodium hybrid Zhongshanshan has been widely planted in the region of Yangtze River for multipurpose of ecological restoration, field shelter, landscape aesthetics as well as carbon sequestration. However, the carbon allocation patterns across distinct stages of stand development of T. Zhongshanshan are poorly documented. Using a sample of 30 trees which were destructively harvested, this study compared 3 models for assessing aboveground biomass. Furthermore, a linear seemingly unrelated regression (SUR) approach was introduced to fit the system of the best selected model that ensured the additivity property. On this basis, biomass and carbon storage of T. Zhongshanshan stands in the Yangtze River Basin (YRB) were fairly estimated. Specifically, the study developed height-diameter at breast (H-DBH) function. The results showed that the selected 3-parameter polynomial model performed better, and the SUR approach provided more accurate estimates of leaf and stem fractions. The total tree biomass was 53.43, 84.87, 140.67, 192.71 and 156.65 t ha⁻¹ in the 9-, 11-, 13-, 15-, and 22-year-old T. Zhongshanshan stands, and contributed averagely 94.40% of the ecosystem biomass accumulation. The current T. Zhongshanshan stands in the YRB area can store 124.76 to 217.64 t ha⁻¹ carbon, of which total tree ranges from 25.32 to 90.89 t ha⁻¹, with 55.19% to 77.66% storing in the soil. The T. Zhongshanshan had continuous potential for carbon storage during its growth, particularly in the incipient stages. The findings of this research are firsthand information for forest managers for the sustainable management of T. Zhongshanshan in the YRB and similar subtropical areas.