Carbon monoxide (CO) as an endogenous gaseous molecule regulates a variety of biological processes in animals. However, CO regulating nutrient stress responses in green alga is largely unknown. On the other hand,
heme oxydase (HO1 as a rate-limiting
enzyme of the first step for
heme degration and to catalyze
heme into
biliverdin (BV), which is concomitant with releasing of CO and ferrous
ions, probably participates in the process of CO-regulating response to nutrient stress in green alga. In this paper, we described an observation that CO could regulate
iron-homeostasis in
iron-starving Chlamydomonas reinhardtii. Exogenous CO at 8 µM was able to prevent the
iron deficient-inducing
chlorosis and improve
chlorophyll accumulation. Expression pattern of FOX1, FTR1 and
ferredoxin was up-regulated by CO exposure in
iron-deficient mediam. treatment with external CO increasing
iron accumulation in
iron-deficient C. reinhardtii. Moreover, to get insights into the regulatory role of HO1, we constructed a transgenic alga overexpressing HO1 and HO1 knock-out mutants. The results show that there was no significant influence on
chlorosis with HO1 overexpression of C. reinhardtii under
iron-deficiency and the
chlorophyll accumulation, and gene expression associated with
iron deficiency of mutant were greatly improved. Otherwise, those results from HO1 knock-out mutants were opposite to HO1 overexpression mutants. Finally, CO exposure induced NO accumulation in cells. However, such an action could be blocked by NO scavenger
cPTIO. These results indicate that CO/HO1 may play an important role in improving green algae adaptation to
iron deficiency or cross-talking with NO under the
iron deficiency.