Sl-SROl1 increases salt tolerance and is a member of the radical-induced cell death 1-similar to RCD1 gene family of tomato

Sl-SROl1 is a salt-regulated gene from Solanum lycopersicon L. that shares amino acid sequence similarity with At-SRO5, a member of the radical-induced cell death 1-similar to RCD1 (RCD-SRO) gene family. The expression of Sl-SROl1 and At-SRO5 was up regulated by salt stress specifically in the roots and the encoded polypeptides share common functions as assessed by over-expressing both genes in wild-type Arabidopsis and in sro5, a T-DNA insertion knockout for At-SRO5. Over-expression of At-SRO5 reduced the H2O2 content of WT salt-stressed roots and the high H2O2 levels found in sro5. It also improved the salt tolerance of WT and sro5 plants and, when over-expressed in the WT background, At-SRO5 caused a slight reduction in the sensitivity of root growth to salt stress. Sl-SROl1 also reduced root H2O2 levels and improved salt tolerance when over-expressed in either WT or sro5. Seed germination in the presence of salt was substantially impaired in sro5 indicating a role for At-SRO5 during germination processes. Over-expression of Sl-SROl1 or At-SRO5 greatly improved the germination capacity of sro5 during salt stress. At-SRO5 contains a poly (ADP-ribose) polymerase (PARP) signature, which was also present in Sl-SROl1. These data are discussed in context with the putative PARP function of these polypeptides, which might modify effectors of oxidative stress tolerance.