Our containment trials have established cold tolerance in Nicotiana tabacum osmotin (Nt Osm) transgenic tomato (Solanum lycopersicum L. cv. Pusa Ruby). Though, the stress tolerance mechanisms have been studied at physio-biochemical levels, molecular mechanisms underlying the tolerant response are still not well studied. Therefore, quantitative transcript expression of Osmotin and other stress responsive genes (CBF1, P5CS and APX) was studied in response to cold (4°C; 2 and 24 h) treatment in the transgenic and wild type tomato plants. The expression analysis revealed differential transcript regulation in the transgenic and wild type plants on the cold exposure. In general, the genes were either earlier induced or the extent of fold change in transcript expression over the respective untreated controls was higher in transgenic than in the wild type plants on cold exposure. The transcript expression data also supported the metabolite analysis on free Proline and ascorbate content. The results thus suggest that constitutive over expression of the Osmotin modulate transcript abundance and functional expression products of the other stress responsive genes thereby, imparting cold tolerance in the transgenic tomato plants.
Keywords: Ascorbate; Cold stress; Free Proline; Osmotin; Transcript expression; Transgenic tomato; qRT PCR.