The floral repressors {TEMPRANILLO}1 and 2 modulate salt tolerance by regulating hormonal components and photo-protection in Arabidopsis

Members of the plant specific RAV family of transcription factors regulate several developmental and physi-ological processes. In the model plant Arabidopsis thaliana, the RAV TEMPRANILLO 1 (TEM1) and TEM2control important phase changes such as the juvenile to adult and the vegetative to reproductive transi-tions. Besides their known regulatory function in plant development, a transcriptomics analysis of trans-genic plants overexpressing TEM1 also revealed overrepresentation of Gene Ontology (GO) categoriesrelated to abiotic stress responses. Therefore, to investigate the biological relevance of these TEM-depen-dent transcriptomic changes and elucidate whether TEMs contribute to the modulation of plant growth inresponse to salinity, we analyzed the behavior of TEM gain and loss of function mutants subjected to mildand high salt stresses at different development stages. With respect to increasing salinity, TEM overexpress-ing plants were hypersensitive whereas the tem1 tem2 double mutants were more tolerant. Precisely, tem1tem2 mutants germinated and flowered faster than the wild-type plants under salt stress conditions. Also,tem1 tem2 plants showed a delay in salt-induced leaf senescence, possibly as a consequence of downregu-lation of jasmonic acid biosynthesis genes. Besides a shorter life cycle and delayed senescence, tem1 tem2mutants appeared to be better suited to withstand oxidative stress as they accumulated higher levels ofa-tocopherol (an important antioxidant metabolite) and displayed a slower degradation of photosyntheticpigments. Taken together, our studies suggest novel and crucial roles for TEM in adaptive growth as theymodulate plant development in response to environmental changes such as increasing soil salinity