Up-regulating arginase contributes to amelioration of chilling stress and the antioxidant system in cherry tomato fruits

BACKGROUND: Arginase, which plays an important role in regulating the metabolism of L-arginine (Arg) in mammalian cells, has been reported to be involved in stress responses in higher plants. In view of the well-established roles of polyamines, nitric oxide and proline in plant tolerance to chilling stress, arginase may play an important role in fruit chilling tolerance by regulating the metabolism of Arg. However, the current information available on this is very limited. RESULTS: Cherry tomatoes (Lycopersicon esculentum cv.Messina) at the mature green stage were treated with Arg or N-omega-hydroxy-nor-L-arginine (nor-NOHA) and analysed for chilling injury, electrolyte leakage, malondialdehyde and proline contents and arginase and antioxidant enzyme (superoxide dismutase, catalase, peroxidase and ascorbate peroxidase) activities during cold storage. The effects of low temperature on the transcriptional levels of two arginase genes (LeARG1 and LeARG2) were also evaluated. LeARG1 and LeARG2 expression and arginase activity were significantly induced by low temperature. Compared with the control, Arg treatment alleviated fruit chilling injury, reduced electrolyte leakage, malondialdehyde content and peroxidaseactivity and increased other parameters. Treatment with nor-NOHA caused the opposite effects. CONCLUSION: Up-regulation of arginase activity and gene expression may be a chilling tolerance strategy in cherry tomato fruit. Inhibition of chilling-induced arginase activity could aggravate chilling injury and oxidation damage. Arginase appears to play an important role in the chilling resistance process of cherry tomato fruit induced by Arg. (C) 2010 Society of Chemical Industry