Cystathionine β-synthase (CBS) domains have been identified in a wide range of proteins
of unrelated functions such as, metabolic enzymes, kinases and channels, and usually occur as tandem
repeats, often in combination with other domains. In plants, CBS Domain-Containing Proteins
(CDCPs) form a multi-gene family and only a few are so far been reported to have a role in development
via regulation of thioredoxin system as well as in abiotic and biotic stress response. However,
the function of majority of CDCPs still remains to be elucidated in plants. Here, we report the cloning,
characterization and functional validation of a CBS domain containing protein, OsCBSCBSPB4 from
rice, which possesses two CBS domains and one PB1 domain. We show that OsCBSCBSPB4 encodes
a nucleo-cytoplasmic protein whose expression is induced in response to various abiotic stress conditions
in salt-sensitive IR64 and salt-tolerant Pokkali rice cultivars. Further, heterologous expression of
OsCBSCBSPB4 in E. coli and tobacco confers marked tolerance against various abiotic stresses.
Transgenic tobacco seedlings over-expressing OsCBSCBSPB4 were found to exhibit better growth in
terms of delayed leaf senescence, profuse root growth and increased biomass in contrast to the wildtype
seedlings when subjected to salinity, dehydration, oxidative and extreme temperature treatments.
Yeast-two hybrid studies revealed that OsCBSCBSPB4 interacts with various proteins. Of these, some
are known to be involved in abiotic stress tolerance. Our results suggest that OsCBSCBSPB4 is involved
in abiotic stress response and is a potential candidate for raising multiple abiotic stress tolerant plants.