A putative protein kinase Femu9p contributes to the iron deficiency-inducible expression of FOX1 gene in Chlamydomonas reinhardtii

FOX1 gene encoding a multicopper ferroxidase is vital in iron metabolism in the single-celled green algae Chlamydomonas reinhardtii. Molecular characteristics of this gene have been extensively studied. However, little information is available about its regulatory factors in C. reinhardtii. In this study, we isolated a regulatory mutant of FOX1 gene by using an arylsulfatase gene driven by the FOX1 promoter. The corresponding gene was also identified via thermal asymmetric interlaced polymerase chain reaction and named Femu9p. Gene structure analysis shows that the Femu9p gene encodes a protein of 757 amino acids which was predicted to contain a protein kinase domain. We demonstrate that Femu9p is essential for the regulation of FOX1 gene expression because Femu9p RNAi silencing leads to a significant decrease in FOX1 promoter activity. Moreover, our analysis indicates that Femu9p positively affects total chlorophyll (Ch a+b) content and the regulation of other iron-uptake-related endogenous gene expressions such as FTR1, FEA1, ATX, and NRAMP2 in C. reinhardtii.