Genome-Wide Characterization of ABC Transporter Genes and Expression Profiles in Red Macroalga Pyropia yezoensis Expose to Low-Temperature

Pyropia yezoensis is an important economic macroalga widely cultivated in the East Asia countries of China, Korea, and Japan. The ATP-binding cassette (ABC) transporter gene family is one of the largest transporter families in all forms of life involved in various biological processes. The characteristics of ABC transporter genes in P. yezoensis (PyABC) and their functions in stress resistance, however, remain largely unknown. In this study, PyABCs were identified and characterized their expression patterns under low-temperature stress. A total of 48 PyABCs transporters were identified and divided into eight subfamilies, which are mostly predicted as membrane-binding proteins. The cis-elements of phytohormone and low-temperature response were distinguished in promoter sequences of PyABCs. Transcriptome analysis showed that PyABCs are involved in response to low-temperature stress. Among them, 12 PyABCs were significantly up-regulated after 24 h of exposure to low temperature (2 °C). Further quantitative RT-PCR analysis corroborated the highest expression happened at 24 for detected genes of PyABCC8, PyABCF3, and PyABCI1, extraordinarily for PyABCF3, and followed by decreased expression at 48 h. The expression of PyABCI1 was generally low in all tested strains. Whereas, in a strain of P. yezoensis with lower tolerance to low temperature, the expression was observed higher in PyABCC1, PyABCC8, and remarkably high in PyABCF3. This study provided valuable information on ABC gene families in P. yezoensis and their functional characteristics, especially on low-temperature resistance, and would help to understand the adaptive mechanisms of P. yezoensis to adverse environments.