Over-expression of SINAL7 increases biomass and drought tolerance, and also delays senescence in Arabidopsis

The seven in absentia like 7 gene (At5g37890, SINAL7) from Arabidopsis thaliana encodes a RING finger protein belonging to the SINA superfamily that possesses E3 ubiquitin-ligase activity. SINAL7 has the ability to self-ubiquitinate and to mono-ubiquitinate glyceraldehyde-3-P dehydrogenase 1 (GAPC1), suggesting a role for both proteins in a hypothetical signaling pathway in Arabidopsis. In this study, the in vivo effects of SINAL7 on plant physiology were examined by over-expressing SINAL7 in transgenic Arabidopsis plants. Phenotypic and gene expression analyses suggest the involvement of SINAL7 in the regulation of several vegetative parameters, essentially those that affect the aerial parts of the plants. Over-expression of SINAL7 resulted in an increase in the concentrations of hexoses and sucrose, with a concommitant increase in plant biomass, particularly in the number of rosette leaves and stem thickness. Interestingly, using the CAB1 (chlorophyll ab binding protein 1) gene as a marker revealed a delay in the onset of senescence. Transgenic plants also displayed a remarkable level of drought resistance, indicating the complexity of the response to SINAL7 over-expression.