Interaction Between Heme Oxygenase And Calaium Signal Mediates Salinity Acclimation In Wheat Seedlings

In animals, it was well known that heme oxygenase (HO, EC1.14.99.3) exists in the variety of tissues and organs of human body, and also has a wide range of physiological functions. Nowadays, HO has been considered to be an antioxidant enzyme and stress protein, and it degrades heme to biliverdin-IXa (BV), carbon monoxide (CO) and Fe iron. Recent results also discovered that HO-1inducer hematin (Ht) can reversal in root growth inhibition and enhance the K/Na ratio of wheat seedling roots, thus maintaining ion homeostasis. Additionally, other results also discovered that CO might confer an increased tolerance against salinity stress by maintaining ion homeostasis and enhancing antioxidant system in wheat seedling roots. Meanwhile, existing results shows that an appropriate concentration of exogenous Ca2+can increase K/Na in barley roots, thus increased salt tolerance. However, it is not clear whether HO was able to improve plant salt-tolerance by the modulation of calcium signaling. Therefore, we examined the interrelationship between HO and calcium signaling in salinity acclimation in wheat seedlings.In present study, we discovered that20mM NaCl pretreatment24h not only increase seedlings growth, relative water content (RWC) and the K to Na ratio of wheat seedling roots, but also reversal in salnity-induced lipid peroxidation in a time-dependent fashion. Further analyses also showed that20mM NaCl pretreatment induced the activity of HO as well as an increase in calcium contents in wheat seedling roots. Whereas,200mM NaCl treatment leads to the opposite effects.Furhter experiment also illustrated that0.5mM Ca2+chelator EGTA,100μM channel blocker La3+and ruthenium red (RR) pretreatment led to a significant decrease in HO activity and down-regulation of HO-1gene transcripts and its protein expression induced by20mM NaCl, as well as decreased shoot, root dry weight and relative water content.It was further found that exogenous applied10mM Ca2+pretreatment resulted in a significant reversal in dry weight and relative water content caused by200mM NaCl, which was related to the up-regulation of HO activity and the increase of HO-1transcripts and its protein expression. We also noted that the application of5μM HO-1inducer hematin not only up-regulation of HO-1gene transcripts and its protein expression, but also led to the reversal of growth inhibition and relative water content decrease in wheat seedling. Additionally, pretreatment with5μM Ht could result in a significantly increase in Ca content in wheat seedling roots.Overall, the above studies suggested clearly that the interaction between HO and calcium signal might mediate salinity tolerance in wheat seedlings.