Abstract:
The B-box (BBX) proteins are a subgroup of zinc finger transcription factors that contain
one or two B-box domains. The B-box domain is a conserved motif. Genes that encode
for BBX proteins are highly conserved across all multicellular species. BBX proteins
were first identified in Arabidopsis thaliana that play a significant role in light and abiotic
stress signalling. In Oryza sativa (rice) only a few BBX genes have been identified which
are involved in flowering. Our previous study on ortholog search identified OsBBX13 as a
functional ortholog of the Arabidopsis AtBBX21 gene that is involved in light and abiotic
stress regulation. This study aimed to conduct an in silico analysis of the OsBBX13 gene
promoter to identify the presence of abiotic stress-responsive elements and to study the
expression of the OsBBX13 gene under salinity stress. Promoter sequence (1.0 kb
upstream of translation start site) of the OsBBX13 gene was retrieved from the Rice
Annotation Project Database (RAP-DB). The tools of PlantCARE and New PLACE were
used for scanning of abiotic stress-responsive cis-elements present on the promoter region
of OsBBX13. The salinity stress-responsive elements, MYBCORE and GT1GMSCAM4,
and Abscisic acid-responsive element (ABRE) which regulates the dehydration and
salinity responses were identified in OsBBX13 promoter region. Quantitative Real Time
PCR analysis of 7 days old rice seedlings exposed to 200 mM NaCl stress showed
significant up-regulation of the OsBBX13 gene compared to the control. All these findings
together suggested that the OsBBX13 gene is involved in salinity stress responses in rice.
Keywords: BBX proteins, OsBBX13, Salinity stress, Abiotic stress
