Iron deficiency response gene Femu2 plays a positive role in protecting Chlamydomonas reinhardtii against salt stress

Background: Iron deficiency related gene, Femu2, encodes protein homologous to a C2H2-type zinc finger protein, which participates in the regulation of FOX1 gene induced by iron (Fe) deficiency in Chlamydomonas reinhardtii. In this study, we investigate the gene function of Femu2 in response to salt stress in C. reinhardtii. Methods: Femu2-overexpressing and Femu2-silencing transgenic cells were analyzed under salt stress. Several physiological indices were measured, and global changes in gene expression were investigated via RNA-seq. Results: Compared with that of the non-treated control, the transcript levels of Femu2 were dramatically induced by iron deficiency and can also be significantly induced after algal cell exposure to Tris acetate phosphate (TAP) medium with 100 and 150 mM NaCl. The promoter also responded to NaCl induction. Femu2-overexpressing transgenic algal cells exhibited significantly enhanced tolerance to salt stress. Conversely, Femu2-silencing cells showed higher sensitivity to salt stress than the control. Physiological analyses revealed that the overexpression of Femu2 increased the contents of proline and soluble sugars in transgenic cells under high salinity and that silencing Femu2 resulted in increased malondialdehyde level and decreased superoxide dismutase activity. RNA-seq results showed that a total of 248 genes have opposite expression profiles and that 5508 and 2120 genes were distinctly up-regulated or down-regulated in Femu2-overexpressing and Femu2-silencing transgenic cells under salt stress, respectively. Conclusion: Femu2 may play an important positive role in protecting C. reinhardtii against salt stress. General Significance: The results of this study indicated that Femu2 may be useful in improving plant salt tolerance. (C) 2016 Elsevier B.V. All rights reserved.