Functional annotation and characterization of hypothetical protein involved in blister blight tolerance in tea (Camellia sinensis (L) O. Kuntze)

Tea [Camellia sinensis (L) O. Kuntze], worldwide known source of popular non-alcoholic beverage, is severely affected by various biotic and abiotic stresses. Among these, blister blight (BB) disease caused by the obligate biotrophic fungus Exobasidium vexan is responsible for significant depletion of its yield and quality. Our comparative NGS transcriptomic analysis although elucidated global gene expression pattern of BB defense transitions, yet left with 12,022 transcripts categorized as ‘hypothetical proteins (HPs)’. In this study, efforts were made for assigning functions to HPs derived from RNA-Seq data and successfully identified novel putative candidates involved in BB defense in tea. Domain and family-based characterization identified 9390 HPs representing 2867 protein families and 953 super families. Of these, 213 HPs were assigned with novel putative defense related functional categories (LRR, WRKY, NAC, chitinases and peroxidases). Further, sub-cellular localization (cytosolic,133 HPs; transmembranic, 80 HPs) with abundance of HPs exhibiting of acidic (133) and basic (80) nature suggests their wider functional range. 36 HPs upregulated in tolerant genotype having significant interactions with defense responsive candidates in Protein–Protein Interaction Network analysis, possibly suggests their key regulatory role in BB defense. Interestingly, 12 stereo-dynamically stable structures [LRR (5), NAC (4), WRKY, Chitinase & Peroxidase (1 each)] of HP’s were successfully modelled based on their conserved signature sequences and empirically validated using qRT-PCR analysis, therefore, can be potential novel candidates possibly involved in signal transduction and pathogen recognition during BB defense in tea. Futuristically, novel genes identified in this study can be potentially utilized to expedite genetic improvement efforts in tea. The approach successfully employed in tea can also be adopted for assigning molecular function to the HPs in other plant species.