Effects of iron on the physiological responses and gene expression of <i>Alexandrium catenella</i> (Dinophyceae)

Summary Iron is essential for the growth and metabolism of marine algae. It also participates in the biosynthesis pathway of saxitoxins in dinoflagellates. High iron concentration may enhance the biosynthesis of saxitoxin in Alexandrium species. To better understand the effect of iron on the growth and metabolism of Alexandrium species, the dominant red tide species in Korea, A. catenella , was cultivated at four different iron concentrations (1, 10, 100, and 1000 nM). The growth data show that, within the range from 1 to 100 nM, growth was positively correlated with the iron concentration. High iron concentration (1000 nM) inhibited the growth of A. catenella. The data from the photosynthesis analysis showed that iron enhanced the maximum relative electron transport rate when the concentration was not higher than 100 nM. A similar result was also found in chlorophyll a content. At the same time, the expressions of several genes related to photosynthesis and saxitoxin synthesis were analyzed at three iron concentrations (1, 10 and 100 nM). The results show that psbE , a gene encoding iron‐binding protein in photosystem II, was significantly upregulated at the iron concentration of 100 nM. Our results increase the knowledge of the effects of iron on the growth, photosynthesis, and gene expression of A. catenella .