Low iron-inducible periplasmic proteinIn Chlamydomonas reinhardtii, the gene encoding Fe-assimilating protein 1 is induced by iron deficiency. In green algae, this protein is periplasmic. The two paralogues FEA1 and FEA2 are the major proteins secreted by iron-deficient Chlamydomonas reinhardtii, and both are up-regulated in response to iron deficiency. FEA1 but not FEA2 is up-regulated by high CO2 concentration. Both FEA1 and FEA2 are secreted into the periplasmic space and genetic evidence confirms that their association with the cell is required for growth in low iron.