Expression patterns of putative genes involved in the biosynthesis of indole alkaloids pathway. a, organ-specific expression in roots and leaves of I. indigotica; b, expression pattern of indole biosynthesis genes in I. indigotica hairy roots treated with MeJA for 0 h, 12 h, and 24 h. Expression levels were quantified by qPCR. The level of each gene is relative to that of UBIQUITIN reference. Each data point is the average of three biological repeats. Error bars indicate SDs. N, None detected.