Evaluation of transgenic tomato plants ectopically expressing the rice Osmyb4 gene

The rice Osmyb4 gene, coding for a MYB ranscription factor, is expressed at low levels in rice coleoptiles under normal conditions and strongly induced at 4 8C. Its overexpression in Arabidopsis thaliana plants increases biotic and abiotic stress tolerance and results in the accumulation of several metabolites, essential in defence response. The heterologous expression of the Myb4 transcription factor represents a promising potential approach to improve stress tolerance in crops, avoiding endogenous mechanisms that often co-suppress the transgene of interest. In order to explore the potential of the Osmyb4 gene to enhance tolerance toward multiple stresses in different host plant genomes, we generated transgenic tomato (Solanum lycopersicum L. cv. Tondino) plants. Like Arabidopsis, tomato plants overexpressing Osmyb4 acquired a higher tolerance to drought stress and to virus disease. However, the transgenic plants did not appear to be more cold tolerant than the WT, in any tested condition. The data obtained indicate that the specificity and the degree of Osmyb4 activity depend on the host genomic background.