Related to APETALA2.1, an interacting protein of alcohol dehydrogenase 1, is crucial for the flooding-stress responses in Taxodium hybrids.

Taxodium hybrid 'Zhongshanshan 406' (T. mucronatum♀ × T. distichum♂) is an excellent clone from the interspecific hybridization of Taxodium, which has a remarkable flooding tolerance level. The key energy supply gene in the glycolysis pathway of T. hybrid 'Zhongshanshan 406', alcohol dehydrogenase 1 (ThADH1) gene, plays an important role in the process of resisting flooding stress. Here, a cDNA library of T. hybrid 'Zhongshanshan 406' under flooding stress was constructed and screened. Several proteins interacting with ThADH1 were identified using yeast two-hybrid methods. In particular, an ethylene transcription factor, RELATED TO APETALA2.1 (ThRAP2.1), was identified as the interaction partner of ThADH1 using bimolecular fluorescence complementation. Under long-term flooding stress of 0-50 days, the expression level of ThRAP2.1 in roots, stems, and leaves showed an upward trend. ThRAP2.1 overexpression in poplar improved the flooding tolerance, increased 1-aminocyclopropane-1-carboxylic acid (ACC) content, ACC synthase (ACS) and ADH enzyme activities, and the ThADH1 expression level under flooding stress. This is the first report on the interaction between two flooding-tolerance-related proteins in woody plants. Screening for ThADH1 interacting proteins and analyzing their flooding tolerance will provide new gene resources for the regulation of flooding tolerance in woody plants and a theoretical basis for further understanding the mechanism of flooding tolerance in Taxodium.