Analysis of transcriptional and upstream regulatory sequence activity of two environmental stress-inducible genes, NBS-Str1 and BLEC-Str8, of rice.

Two abiotic stress-inducible upstream regulatory sequences (URSs) from rice have been identified and functionally characterized in rice. NBS-Str1 and BLEC-Str8 genes have been identified, by analysing the transcriptome data of cold, salt and desiccation stress-treated 7-day-old rice (Oryza sativa L. var. IR64) seedling, to be preferentially responsive to desiccation and salt stress, respectively. NBS-Str1 and BLEC-Str8 genes code for putative NBS (nucleotide binding site)-LRR (leucine rich repeat) and β-lectin domain protein, respectively. NBS-Str1 URS is induced in root tissue, preferentially in vascular bundle, during 3 and 24 h of desiccation stress condition in transgenic 7-day-old rice seedling. In mature transgenic plants, this URS shows induction in root and shoot tissue under desiccation stress as well as under prolonged (1 and 2 day) salt stress. BLEC-Str8 URS shows basal activity under un-stressed condition, however, it is inducible under salt stress condition in both root and leaf tissues in young seedling and mature plants. Activity of BLEC-Str8 URS has been found to be vascular tissue preferential, however, under salt stress condition its activity is also found in the mesophyll tissue. NBS-Str1 and BLEC-Str8 URSs are inducible by heavy metal, copper and manganese. Interestingly, both the URSs have been found to be non responsive to ABA treatment, implying them to be part of ABA-independent abiotic stress response pathway. These URSs could prove useful for expressing a transgene in a stress responsive manner for development of stress tolerant transgenic systems.