Glutathione transferase supergene family in tomato: Salt stress-regulated expression of representative genes from distinct GST classes in plants primed with salicylic acid

A family tree of the multifunctional proteins, glutathione transferases (GSTs, EC 2.5.1.18) was created in Solanum lycopersicum based on homology to known Arabidopsis GSTs. The involvement of selected SIGSTs was studied in salt stress response of tomato primed with salicylic acid (SA) or in un-primed plants by real-time qPCR. Selected tau GSTs (SIGSTU23, SIGSTU26) were up-regulated in the leaves, while GSTs from lambda, theta, dehydroascorbate reductase and zeta classes (SIGSTL3, SIGSTT2, SIDHAR5, SIGSTZ2) in the root tissues under salt stress. Priming with SA exhibited a concentration dependency; SA mitigated the salt stress injury and caused characteristic changes in the expression pattern of SIGSTs only at 10(-4) M concentration. SIGSTF4 displayed a significant up-regulation in the leaves, while the abundance of SIGSTL3, SIGSTT2 and SIGSTZ2 transcripts were enhanced in the roots of plants primed with high SA concentration. Unexpectedly, under high salinity the SIDHAR2 expression decreased in primed roots as compared to the salt-stressed plants, however, the up-regulation of SIDHAR5 isoenzyme contributed to the maintenance of DHAR activity in roots primed with high SA. The members of lambda, theta and zeta class GSTs have a specific role in salt stress acclimation of tomato, while SIGSTU26 and SIGSTF4, the enzymes with high glutathione conjugating activity, characterize a successful priming in both roots and leaves. In contrast to low concentration, high SA concentration induced those GSTs in primed roots, which were up-regulated under salt stress. Our data indicate that induction of GSTs provide a flexible tool in maintaining redox homeostasis during unfavourable conditions. (C) 2014 Elsevier Masson SAS. All rights reserved.