Heme Oxygenase Is Involved In Jasmonic Acid-and Hemin-β-Cyclodextrin-Induced Tomato Lateral Root Development

Heme oxygenase (HO) has been proved to be an important signaling system, and plays a putative role in mammalian and plants. Recently, the role of endogenous heme oxygenase-1(HO-1EC1.14.99.3) in lateral root formation, adventitious root development, stomata closure and salt tolerance have been evaluated.Jasmonic acid (JA) is an important hormone and modulates plant growth and development extensively. It has been found that jasmonic acid was involved in the development of plant root systems, but its mechanism is unclear. Our study focuses on the relationship between heme oxygenase and jasmonic acid in tomato lateral root formation. It is found that JA not only induces tomato lateral root formation in a dose-dependent manner, but also promotes the HO-1protein expression, activity and LeHO-1/2transcription levels. To further investigate the relationship between the JA and HO, HO-1specific inhibitor ZnPP and HO-1inducer hemin were applied. The results showed that ZnPP can reverse the effects of100nM JA on tomato lateral root formation, HO-1protein expression, HO activity, and LeHO-1/2transcripts. In further research, we also found that JA up-regulates the cell cycle genes LeCDKA1and LeCYCA2;1, and down-regulate LeKRP2to promote lateral roots, and the effect can be reversed by ZnPP.The effects of hemin (H) and hemin-β-cyclodextrin (β-CD/H) on tomato lateral root formation were also investigated in our research. The results showed that hemin and hemin-β-cyclodextrin promotes the lateral root formation, induces HO expression, up-regulates the cell cycle gene transcriptions, such as LeCDKAl and LeCYCA2;1, and down-regulates LeKRP2. But the result also showed that β-cyclodextrin has no effect on lateral root formation or HO-1expression. Compared with the effective concentrations of hemin (10μM) and hemin-β-cyclodextrin (1nM), we had a conclusion that hemin-β-cyclodextrin increases hemin bioavailability of hemin significantly. In addition, HO-1specific inhibitor ZnPP could reverse the tomato lateral root formation induced by hemin-β-cyclodextrin, as well as the changes of the LeHO-1/2transcriptions. Together the above results suggest that HO might be involved in hemin-β-cyclodextrin induced-up-regulation of cell cycle genes and tomato lateral root formation.