Deciphering the complete CDS sequence of Bibenzyl synthase (BBS) gene in Pholidota articulata and its transcriptional regulation under different stress conditions

Bibenzyl synthase (BBS) is one of the key enzymes for the formation of bibenzyls, a class of specialized therapeutic metabolites that are predominantly found in the family Orchidaceae. The present study reports the complete transcript of the BBS gene isolated and sequenced from an ethnomedicinally important orchid, Pholidota articulata Lindl. The BBS transcript of P. articulata (PaBBS) was found to comprise a total of 1494 bp with an open reading frame coding for 390 amino acids. Multiple sequence analysis and phylogenetic analysis highlighted its close association with BBS sequences and type III polyketide synthase (PKS III) genes of other plant species. Three-dimensional structure analysis has revealed that the PaBBS protein is a homodimer with each subunit having a molecular weight of 42.83 KDa. In silico studies of the putative PaBBS protein revealed the presence of the characteristic conserved regions of the BBS enzyme as well as the PKS III superfamily. The present study also revealed that expression PaBBS is influenced by the age of the plant, tissue type, abiotic stress, and exposure to elicitors. The expression of PaBBS transcript was recorded to be higher in young plantlets as compared to mature plants, and among the plant parts the root tissue exhibited the highest expression. Further, it was found that the expression of PaBBS was upregulated by abiotic stresses such as wounding and heat treatment, downregulated by high-intensity UV exposure and cold treatment, and increased many-fold when exposed to elicitors like chitosan and yeast extract. The results obtained in the present study provide an understanding of the transcriptional regulation of PaBBS gene which plays a crucial role in the ecological adaptation of P. articulata, an orchid of medicinal importance.