The role of cis -zeatin in enhancing high-temperature resistance and fucoxanthin biosynthesis in Phaeodactylum tricornutum

ABSTRACT Phaeodactylum tricornutum a prominent source of industrial fucoxanthin production, faces challenges in its application due to its tolerance to high-temperature environments. This study investigates the physiological responses of P. tricornutum to high-temperature stress and its impact on fucoxanthin content, with a specific focus on the role of cis -zeatin. The results reveal that high-temperature stress inhibits P. tricornutum ’s growth and photosynthetic activity, leading to a decrease in fucoxanthin content. Transcriptome analysis shows that high temperature suppresses the expression of genes related to photosynthesis (e.g., psbO , psbQ , and OEC ) and fucoxanthin biosynthesis (e.g., PYS , PDS1 , and PSD2 ), underscoring the negative effects of high temperature on P. tricornutum . Interestingly, genes associated with cis -zeatin biosynthesis and cytokinesis signaling pathways exhibited increased expression under high-temperature conditions, indicating a potential role of cis -zeatin signaling in response to elevated temperatures. Content measurements confirm that high temperature enhances cis -zeatin content. Furthermore, the exogenous addition of cytokinesis mimetics or inhibitors significantly affected P. tricornutum ’s high-temperature resistance. Overexpression of the cis-zeatin biosynthetic enzyme gene tRNA DMATase enhanced P. tricornutum ’s resistance to high-temperature stress, while genetic knockout of tRNA DMATas e reduced its resistance to high temperatures. Therefore, this research not only uncovers a novel mechanism for high-temperature resistance in P. tricornutum but also offers a possible alga species that can withstand high temperatures for the industrial production of fucoxanthin, offering valuable insights for practical utilization. IMPORTANCE This study delves into Phaeodactylum tricornutum ’s response to high-temperature stress, specifically focusing on cis -zeatin. We uncover inhibited growth, reduced fucoxanthin, and significant cis -zeatin-related gene expression under high temperatures, highlighting potential signaling mechanisms. Crucially, genetic engineering and exogenous addition experiments confirm that the change in cis -zeatin levels could influence P. tricornutum ’s resistance to high-temperature stress. This breakthrough deepens our understanding of microalgae adaptation to high temperatures and offers an innovative angle for industrial fucoxanthin production. This research is a pivotal step toward developing heat-resistant microalgae for industrial use.