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Heme oxygenese has recently been proved to be an important signal molecule in mammalian cells, and plays a putative role in keeping cell survival and stabilization. Recently, some results proved that HO was involved in modulating the tolerance of salt stress, inducing stomata closure and promoting adventitious roots development.To elucidate the function of HO in the development of lateral toot induced by salinity, we identify the effects of endogenous HO induced by NaCl on lateral root formation and its signal transduction. In this report, we discovered that NaCl induced lateral root development in a dose-dependent manner, also increased LeHO-1/2 transcripts and HO-1 protein expression. In order to check whether HO is involved in the lateral rooting process, HO-1 specific inhibitor ZnPP and HO-1 inducer hemin was applied. The application of ZnPP could reverse the inducing effects of 5 mM NaCl, and hemin could recover the inhibition effects of 25 mM NaCl on lateral root development and HO activity. The molecular mechanism further indicates that NaCl promotes the development of lateral root by up-regulating cell cycle gene LeCYCD3;1, LeCDKAl, LeCYCA2;1 and LeCYCA3;1, and down-regulating LeKRP2 transcripts, while ZnPP reverses the effects. Thus, above results indicate that HO was involved in NaCl-induced lateral root development by modulating cell cycle gene expression.Moreover, we investigated the role of H2O2 in tomato lateral rooting process. The fluorescence detection results found that salt-induced H2O2 could be scavenged by the H2O2 scavenger CAT and DMTU, leading to the reduction of lateral root formation. CAT and DMTU could also inhibit HO transcripts, HO-1 protein expression and HO activity. Exogenous H2O2 treatment could mimic the effects of endogenous H2O2 on the formation of tomato lateral root and HO expression. It was also found that H2O2 promotes the development of lateral root by up-regulating cell cycle gene LeCYCD3;1 and LeCDKAl and down-regulating LeKRP2 transcripts, while ZnPP reverses these effects. These suggest that H2O2 may act as the upstream signal molecule of HO action.Taken together, we provided pharmacological, physiological and molecular evidence that the signal transduction in lateral root development is mediated by NaCl→H2O2→HO→LR development.
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