Abstract: Fasciclin-like arabinogalactan proteins (FLAs) play an important role in the growth and development of plants under stresses. However, it is unclear whether FLAs are involved in the adaptation mechanism of endangered mangrove species Acanthus ebracteatus in the intertidal marine habitat. In this study, we cloned the AeFLA17 gene from A. ebracteatus, investigated its tissuespecific expression across different organs and spatiotemporal expression patterns during floral development, and further analyzed its expression profiles in the leaves under various abiotic stresses, including high temperature, low temperature, salt, drought, waterlogging, and cadmium. The results showed that the AeFLA17 gene is 2194 bp in length, contains a complete coding sequence of 1410 bp, encoding 469 amino acids with no introns, and is a hydrophilic and unstable protein. Phylogenetic analysis indicated that AeFLA17 was closely related to the FLA protein of Andrographis paniculata in the family Acanthaceae. Subcellular localization revealed that the AeFLA17 protein was localized in the cytoplasm. Quantitative real-time PCR experiments indicated that the AeFLA17 gene showed the lowest expression level in the leaves and the highest in the flowers of A. ebracteatus, with peak expression observed during the full bloom stage. The expression of AeFLA17 was significantly upregulated at 12 h, but rapidly decreased after 24 h. It slightly recovered at 48 h but did not reach a significant level under heat stress. Under cold stress, the expression level increased significantly after 24 h and continued to increase. After 48 h of cadmium stress treatment, the expression level was significantly up-regulated. However, under drought stress, the expression level at both 24 and 48 h showed obvious inhibition. Under flooding stress and salt stress, the gene expression showed a gradual decrease trend with the extension of stress time. This dynamic expression of AeFLA17 reveals its role in the plant response network to multiple stresses, providing an important theoretical basis for further analysis of the function of the FLA protein family and molecular breeding for stress resistance.

Key words: Acanthus ebracteatus, fasciclin-like arabinogalactan proteins (FLAs), gene cloning, abiotic stress, subcellular localization