Effects of Photoperiods on the Pigment Composition in Marine Diatom Phaeodactylum tricornutum
Description
Diatoms are crucial photoautotrophic phytoplankton, playing a vital role in marine ecosystems due to their efficient photosynthesis and ability to adapt to fluctuating light environments. The light adaptation of diatoms is primarily regulated by pigments, which not only form light-harvesting complexes but also participate in photoprotective mechanisms. Light-dark (LD) cycles are key environmental factors regulating diatom physiology. In recent years, the antioxidant, UV-protective, and anti-inflammatory properties of diatom pigments have been increasingly recognized, highlighting their growing application value. Understanding how diatoms regulate pigment biosynthesis under different LD cycles is crucial for both theoretical and applied research. In this study, the model diatom Phaeodactylum tricornutum was used to investigate the regulation of pigment synthesis under different LD cycles (LD 24:0, LD 16:8, LD 12:12, LD 8:16, LD 4:2, LD 2:2, and LD 2:4). Physiological responses, including growth rate, pigment composition, photosynthetic parameters, and elemental composition, were assessed alongside transcriptomic analysis. The results demonstrated that intermittent light enhanced growth rate to some extent, with peak pigment content observed under the LD 2:2 condition. Additionally, intermittent light increased the ratio of photosynthetic to photoprotective pigments while reducing the de-epoxidation level of diadinoxanthin. Pigment composition exhibited phase-specific variations: chlorophyll a dominated in the exponential phase, while fucoxanthin increased in the stationary phase. Photosynthetic parameters indicated higher efficiency under intermittent light, while the LD 24:0 group exhibited the lowest values. Transcriptomic analysis revealed that moderate-length LD cycles (LD 2:2 and LD 12:12) significantly upregulated genes involved in carotenoid biosynthesis, chlorophyll biosynthesis, and light-harvesting complex proteins. This study offers theoretical support for understanding diatom light adaptation strategies and their application research.