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Genome-wide analysis of thiourea-modulated salinity stress-responsive transcripts in seeds of Brassica juncea: identification of signalling and effector components of stress tolerance

Srivastava, A.K., Ramaswamy, N.K., Suprasanna, P., D'Souza, S.F.
Annals of botany 2010 v.106 no.5 pp. 663-674
Brassica juncea, abscisic acid, calcium, crop production, gene expression, gene expression regulation, genes, glutathione, mechanism of action, microarray technology, phenylalanine ammonia-lyase, polymerase chain reaction, proteins, salinity, salt stress, salt tolerance, seeds, sodium chloride, stress tolerance, transcription factors
BACKGROUND AND AIMS: Abiotic stresses including salinity are the major constraints to crop production. In this regard, the use of thiourea (TU) in imparting salinity-stress tolerance to Indian mustard (Brassica juncea) has been demonstrated earlier. To gain an insight into the mechanism of TU action, various molecular and biochemical studies were conducted. METHODS: Microarray analysis was performed in seeds subjected to distilled water (control), 1 M NaCl, 1 M NaCl + 6·5 mM TU and 6·5 mM TU alone for 1 h. Real-time PCR validation of selected genes and biochemical studies were conducted under similar treatments at 1 h and 6 h. KEY RESULTS: The microarray analysis revealed a differential expression profile of 33 genes in NaCl- and NaCl + TU-treated seeds, most of which are established markers of stress tolerance. The temporal regulation of eight selected genes by real-time PCR indicated their early and co-ordinated induction at 1 h in NaCl + TU only. Besides, NaCl + TU-treated seeds also maintained a higher level of abscisic acid, reduced to oxidized glutathione (GSH : GSSG) ratio and activities of catalase, phenylalanine ammonia lyase and glutathione-S-transferases, as compared with that of NaCl treatment. The addition of LaCl₃ (a specific calcium-channel blocker) restricted the responses of TU both at molecular and biochemical level suggesting the possible involvement of a cytosolic calcium burst in the TU-mediated response. The TU-alone treatment was comparable to that of the control; however, it reduced the expression of some transcription factors and heat-shock proteins presumably due to the stabilization of the corresponding proteins. CONCLUSIONS: The TU treatment co-ordinately regulates different signalling and effector mechanisms at an early stage to alleviate stress even under a high degree of salinity. This also indicates the potential of TU to be used as an effective bioregulator to impart salinity tolerance under field conditions.