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Effect of exogenous arginine pre-treatment on some physiological parameter and the expression of arginase I and II genes in tomato plant under drought stress

Fatemeh Nasibi, Mohammad Mehdi Yaghoobi, Khosrow Manouchehri Kalantari, Pariya Pirooz

In this research,we have used arginine as a precursor of nitric oxide synthase and Nw-Nitro- L-ArginineMethyl Ester (LNAM) as an inhibitor of NOS, and the effect of these compound on alleviation of oxidative damages under drought stress has been investigated. The result showed that relative water content andmembrane stability index increased when tomato plants treated withArg. These results correspond wellwith lipoxygenase activity, which the activity of this enzyme decreased in plants, which were pretreated with Arg. In this research drought stress increased the activity of PAL and total phenol content, but arginine pretreatment had no effect on PAL activity and total phenol content. Our findings showed that the effects ofArg andArg+LNAMpretreatment had the same effects onmany parameters, and it seems that in these situations other pathways of Arg metabolism rather than NOS may activate. Increment in proline content and the molecular analysis of this research confirm this idea because in the Arg pretreated plants, the expression of arginase ² and ²² genes were higher than the non -Arg pretreated plants. Therefore, it seems that under these situations, protective effect of Arg is related to polyamines and or proline biosynthesis.