A glutathione S-transferase gene from Lilium regale Wilson confers transgenic tobacco resistance to Fusarium oxysporum

Abstract

Glutathione S-transferases (GSTs) are multifunctional proteins that are encoded by a large gene family. Plant GSTs are involved in host defense against both biotic and abiotic stresses as well as are involved in some physiological processes under normal conditions. In the present study, a novel tau GST gene, LrGSTU5, was isolated from Lilium regale Wilson. The deduced protein LrGSTU5 shared a high identity with AcGSTU1 from Allium cepa. In addition, there was relatively high gene expression of LrGSTU5 in the roots but the only minimal expression in both the stem and leaf of L. regale under normal conditions. The gene expression of LrGSTU5 was obviously up-regulated after treatment with signaling molecules including salicylic acid and ethylene as well as after inoculation with Fusarium oxysporum. Furthermore, in order to verify the function of LrGSTU5, a constitutive plant expression vector of LrGSTU5 was constructed and transferred into tobacco (Nicotiana tabacum L. cv Xanthi). Compared to the wild type (WT), several diseases resistance-related genes, including osmotin, PR1b, chitinase, and MnSOD, were up-regulated in the transgenic lines. Moreover, three important antioxidant enzymes, GST, superoxide dismutase, and ascorbate peroxidase, exhibited significantly higher activities in the T1 transgenic lines than in the WT after inoculation with F. oxysporum. Meanwhile, the rate of superoxidate anion production in the transgenic tobacco lines was significantly lower than in the WT. The antifungal activity of three LrGSTU5 transgenic tobacco lines was estimated through in vivo inoculation, and the results showed that the transgenic tobacco plants enhanced the resistance to F. oxysporum.