Involvement of haem oxygenase-1 in hydrogen peroxide-induced lateral root formation in tomato

Abstract

The objective of this study was to test whether haem oxygenase-1 (HO-1) is involved in hydrogen peroxide (H2O2)-induced lateral root (LR) formation. The results showed that 0.1 mM H2O2 mimicked the effects of the HO-1 inducer, haemin, on the up-regulation of tomato HO-1 (SlHO1) expression, increased carbon monoxide (CO) synthesis and LR formation. However, 1.0 mM H2O2 resulted in inhibitory responses. The above inducible or inhibitory responses elicited by 0.1 and 1.0 mM H2O2 were noticeably blocked or rescued by the HO-1 inhibitor zinc protoporphyrin IX (ZnPP) or haemin, and then separately reversed by CO or ZnPP. Further trials showed that haemin-induced responses were not altered by the H2O2 trap, dimethylthiourea (DMTU). When applied alone, DMTU not only decreased H2O2 contents but also inhibited SlHO1 expression and LR development. These responses were recovered by the application of haemin or CO. Molecular evidence revealed that H2O2-modulated expression of the target genes responsible for LR formation was blocked by ZnPP, but rescued by CO. Salinity-induced up-regulation of HO-1 expression and thereafter LR formation were also dependent on the H2O2 generation. Overall, these results demonstrated a possible role of HO-1 in the H2O2-induced tomato LR formation.