Gene expression analysis in drought tolerant and susceptible black pepper (Piper nigrum L.) in response to water deficit stress

Drought or water deficit stress is one of the main environmental stresses affecting plants, resulting in reduced productivity and crop loss. Black pepper, a major spice cultivated across the globe, is drought sensitive and water stress often results in plant death. The present study compared the difference in physiological parameters: relative water content (RWC) and cell membrane leakage, and also analyzed the differential expression of 11 drought responsive genes in drought tolerant and drought sensitive black pepper genotypes. Tolerant black pepper genotype exhibited significantly higher RWC and lower cell membrane leakage 10 days after stress induction than the sensitive genotype. The relative expressions of the 11 selected drought responsive genes were normalized against ubiquitin and RNA-binding protein which was identified as the most stable reference genes in black pepper under the present experimental condition using the RefFinder software. Dehydrin showed the highest transcript accumulation in both the black pepper genotypes under drought stress condition and the relative expression of the gene was higher in the tolerant genotype compared to the susceptible. Similar pattern of higher relative expression was also observed in the stress responsive gene, osmotin. The membrane protein aquaporin and the transcription factor bZIP were relatively down-regulated in the tolerant genotype. The differential expression of these important drought responsive genes in tolerant genotype of black pepper indicates its further usefulness in developing varieties with improved water stress tolerance.