RESUMO
BACKGROUND AND AIMS: Large areas of the globe are becoming saline due to evapotranspiration and poor irrigation practices, and sustainability of agriculture is being seriously affected. Thiourea (TU) has been identified as an effective bioregulator imparting stress tolerance to crops. The molecular mechanisms involved in the TU-mediated response are considered in this study. METHODS: Differential display was performed in order to identify TU-modulated transcripts in Brassica juncea seeds exposed to various treatments (distilled water; 1 m NaCl; 1 m NaCl + 500 p.p.m. TU). The differential regulation of these transcripts was validated by quantitative real-time PCR. KEY RESULTS: Thiourea treatment maintained the viability of seeds exposed to NaCl for 6 h. Expression analysis showed that the transcript level of alpha, beta, gamma, delta and epsilon subunits of mitochondrial ATPase (mtATPase) varied in seeds subjected to the different treatments for 1 h: expression level was significantly altered by 1 m NaCl relative to controls; however, in the NaCl + TU treatment it reverted back in an integrated manner. Similar results were obtained from time-kinetics studies of beta and delta subunits in roots of 8-d-old seedlings. These observations were also confirmed by the mtATPase activity from isolated mitochondria. The reversal in the expression and activity profile of mtATPase through the application of a bioregulator such as TU is a novel finding for any plant system. CONCLUSIONS: The results suggest that TU treatment maintains the integrity and functioning of mitochondria in seeds as well as seedlings exposed to salinity. Thus, TU has the potential to be used as an effective bioregulator to impart salinity tolerance under field conditions, and might prove to be of high economic importance by opening new avenues for both basic and applied research.