CHARACTERIZATION OF A HEME OXYGENASE-1 FROM TOBACCO THAT IS INVOLVED IN SOME ABIOTIC STRESS RESPONSES

摘要

Heme oxygenase-1 (HO1) is a stress protein induced by a variety of oxidative challenges. In this study, an NtHOl gene coding for a tobacco (Nicotiana tabacum L.) HOI was identified. The NtHOl gene encodes an NtHOl precursor of 32.1 kDa with a putative N-terminal plastid transit peptide. The three-dimensional structure of NtHO1 was modeled, and it showed a high degree of structural conservation compared with the known animal and bacterial HO1 crystal structures. Phylogenetic analysis revealed that NtHOl clearly groups with the HO1-like sequences. The recombinant mature NtHOl protein expressed heterologously in Escherichia coli was active in the conversion of heme to biliverdin IXα. The result of subcellular localization of NtHO1 confirmed the presence of a functional transit peptide and implied that the NtHO1 gene product is at least localized in the chloroplast. Expression analysis showed that NtHOl was expressed in all tissues tested. Importantly, we found that NtHOl expression could be induced by osmotic and salinity stresses, cadmium exposure, hydrogen peroxide, and hemin, suggesting that NtHO1 might play an important role in abiotic stress response. These findings regarding NtHO1 will facilitate our knowledge of its roles under various abiotic stress conditions.