The SUI-homologous translation initiation factor eIF-1 is involved in regulation of ion homeostasis in rice

Halophytes survive high salinity by using complex adaptive mechanisms. In a search for novel molecular mechanisms involved in salt acclimation, transcript analyses revealed increased expression of a SUI-homologous translation initiation factor eIF-1 in the salt-tolerant grass species Festuca rubra ssp. littoralis but not in rice. Upon analysis of the cell specificity of eIF-1 transcription by in situ polymerase chain reaction (PCR), predominant signals were detected in rice leaf mesophyll. To further examine the role of eIF-1 in salt tolerance, transgenic rice plants were generated that over-express this factor under the control of the CaMV-35S promoter. The eIF-1 over-expressing lines showed improved growth under salt stress that was correlated with maintenance of photosynthetic activity and reduced Na(+) and Cl(-) accumulation in leaves. The transgenic rice lines also activated expression of the vacuolar H(+)-ATPase. In addition, an oxidoreductase that belongs to the aldo/keto reductase family was identified as a gene with modified expression in the eIF-1 over-expressing lines, compared with wild-type rice. Our data suggest that eIF-1 has a central function in salt-stress adaptation in rice by regulating ion accumulation and the intracellular redox status.