ABSTRACT
In animals, heme oxygenase (HO), a rate-limiting enzyme responsible for carbon monoxide (CO) production, was regarded as a protective system maintaining cellular homeostasis. It was also established that metal ions are powerful HO-inducing agents and cobalt chloride (CoCl(2)) was the first metal ion identified with an inducing property. Previous study suggests that CoCl(2) stimulates adventitious root formation in tomato and cucumber cuttings. In this test, we discover that both CoCl(2) and an inducer of HO-1, hemin, could lead to the promotion of lateral root development, as well as the induction of HO-1 protein expression, HO activity, or LeHO-1/2 transcripts, in lateral root initiation zone of tomato seedlings. The effect is specific for HO since the potent HO-1 inhibitor zinc protoporphyrin IX (ZnPPIX) blocked the above actions of CoCl(2), and the inhibitory effect was reversed partially when 50% CO aqueous solution was added. However, the addition of ascorbic acid (AsA), a well-known antioxidant, exhibited no obvious effect on lateral root formation. Molecular evidence further showed that CoCl(2)-induced the up-regulation of target genes responsible for lateral root formation, including LeCDKA1, LeCYCA2;1, and LeCYCA3;1, was suppressed differentially by ZnPPIX. And these decreases were reversed further by the addition of CO. All together, these results suggest a novel role for HO in the CoCl(2)-induced tomato lateral root formation.
Subject(s)
Cobalt/pharmacology , Heme Oxygenase (Decyclizing)/metabolism , Plant Roots/drug effects , Plant Roots/enzymology , Solanum lycopersicum/drug effects , Solanum lycopersicum/enzymology , Ascorbic Acid/pharmacology , Blotting, Western , Heme Oxygenase (Decyclizing)/genetics , Solanum lycopersicum/metabolism , Plant Proteins/genetics , Plant Proteins/metabolism , Plant Roots/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Seedlings/drug effects , Seedlings/enzymology , Seedlings/metabolismABSTRACT
Indole acetic acid (IAA) is an important regulator of adventitious rooting via the activation of complex signaling cascades. In animals, carbon monoxide (CO), mainly generated by heme oxygenases (HOs), is a significant modulator of inflammatory reactions, affecting cell proliferation and the production of growth factors. In this report, we show that treatment with the auxin transport inhibitor naphthylphthalamic acid prevented auxin-mediated induction of adventitious rooting and also decreased the activity of HO and its by-product CO content. The application of IAA, HO-1 activator/CO donor hematin, or CO aqueous solution was able to alleviate the IAA depletion-induced inhibition of adventitious root formation. Meanwhile, IAA or hematin treatment rapidly activated HO activity or HO-1 protein expression, and CO content was also enhanced. The application of the HO-1-specific inhibitor zinc protoporphyrin IX (ZnPPIX) could inhibit the above IAA and hematin responses. CO aqueous solution treatment was able to ameliorate the ZnPPIX-induced inhibition of adventitious rooting. Molecular evidence further showed that ZnPPIX mimicked the effects of naphthylphthalamic acid on the inhibition of adventitious rooting, the down-regulation of one DnaJ-like gene (CSDNAJ-1), and two calcium-dependent protein kinase genes (CSCDPK1 and CSCDPK5). Application of CO aqueous solution not only dose-dependently blocked IAA depletion-induced inhibition of adventitious rooting but also enhanced endogenous CO content and up-regulated CSDNAJ-1 and CSCDPK1/5 transcripts. Together, we provided pharmacological, physiological, and molecular evidence that auxin rapidly activates HO activity and that the product of HO action, CO, then triggers the signal transduction events that lead to the auxin responses of adventitious root formation in cucumber (Cucumis sativus).
Subject(s)
Carbon Monoxide/metabolism , Cucumis sativus/growth & development , Heme Oxygenase-1/metabolism , Indoleacetic Acids/pharmacology , Plant Roots/growth & development , Cells, Cultured , Cucumis sativus/drug effects , Cucumis sativus/genetics , Cucumis sativus/metabolism , Gene Expression Profiling , Gene Expression Regulation, Plant/drug effects , Hemin/pharmacology , Molecular Sequence Data , Phthalimides/pharmacology , Plant Growth Regulators/pharmacology , Plant Roots/drug effects , Plant Roots/genetics , Plant Roots/metabolism , Protoporphyrins/pharmacology , RNA, Plant/genetics , Reverse Transcriptase Polymerase Chain Reaction , Signal TransductionABSTRACT
The effects and the relationship between soaking rice seed of exogenous glucose, fructose and nitric oxide (NO) donor sodium nitroprusside (SNP) on the seed germination under salt stress were investigated. The results showed that employment of exogenous fructose, glucose and NO donor SNP could significantly promote the germination index and the early germination rate of rice seed under salt stress. Also, SNP pretreatment enhanced endogenous glucose and fructose contents. Effects of exogenous glucose and fructose combined with different concentrations of SNP on the rice seed germination and seedling growth under salt stress were surveyed. The results also showed that there existing positive effect of application of glucose plus SNP on the rice seed germination in comparison with existing a few negative effects of fructose plus SNP pretreatment. Additionally, the alleviation of inhibition of early rice seedling growth under salt stress by SNP could be modulated by glucose and fructose pretreatment, also the effect of glucose was stronger.
