Transcriptome-wide identification and expression analysis of expansin genes in big and small leaf-morphotypes of Adhatoda vasica

In the present study the expansin genes were identified from Adhatoda vasica, a potential medicinal plant. It consists of two morphotypes S (small leaf bearing plants with low alkaloid content) and B (large leaf bearing plants with high alkaloid content). The difference in the leaf size influence the alkaloid content and it act as the economically important trait for this medicinal plant. Therefore, exploring the expression of expansins will facilitate the molecular regulation of leaf expansion in A. vasica. For the identification of expansins, Hidden Markov model (HMM) profiles of double-psi beta-barrel (DPBB) and pollen allergen domains were utilized and searched against the genomes of Arabidopsis thaliana, Catharanthus roseus and Camellia sinensis and confirmed with BLAST search against published expansins of A. thaliana. The resulted expansins were used for homology-based identification of expansin transcripts in A. vasica transcriptome assembly. A total of 22 expansin transcripts were identified in A. vasica leaf transcriptome. The phylogenetic tree illustrated that the expansins were clustered into four subfamily EXPA, EXPB, EXPLA, and EXPLB. Interactome analysis revealed that the expansins interacted with genes involved in cell wall modification. In addition, leaf transcriptome analysis of S and B morphotypes revealed that majority of the expansins were upregulated in B morphotype than S morphotype. Further, qPCR analysis of selected expansin genes from transcriptome were validated in the young and mature leaf tissues of both morphotypes. Overall, the outcomes of the present study will facilitate the understanding the expansins based molecular regulation of leaf size in A. vasica which will aid in the higher production of pharmaceutically important alkaloids.