Genome-wide identification of Avicennia marina aquaporins reveals their role in adaptation to intertidal habitats and their relevance to salt secretion and vivipary.

Aquaporins (AQPs) regulate the transport of water and other substrates, aiding plants in adapting to stressful environments. However, the knowledge of AQPs in salt-secreting and viviparous Avicennia marina is limited. In this study, 46 AmAQPs were identified in A. marina genome, and their subcellular localisation and function in transporting H O and boron were assessed through bioinformatics analysis and yeast transformation. Through analysing their expression patterns via RNAseq and real-time quantitative polymerase chain reaction, we found that most AmAQPs were downregulated in response to salt and tidal flooding. AmPIP (1;1, 1;7, 2;8, 2;9) and AmTIP (1;5, 1;6) as salt-tolerant candidate genes may contribute to salt secretion together with Na /H antiporters. AmPIP2;1 and AmTIP1;5 were upregulated during tidal flooding and may be regulated by anaerobic-responsive element and ethylene-responsive element cis-elements, aiding in adaptation to tidal inundation. Additionally, we found that the loss of the seed desiccation and dormancy-related TIP3 gene, and the loss of the seed dormancy regulator DOG1 gene, or DOG1 protein lack heme-binding capacity, may be genetic factors contributing to vivipary. Our findings shed light on the role of AQPs in A. marina adaptation to intertidal environments and their relevance to salt secretion and vivipary.