An Update on Transcriptome Sequencing of Hairy Root Cultures of Medicinally Important Plants

Abstract

Hairy root cultures induced by Agrobacterium rhizogenes infection have been recognized as promising and attractive alternative source of secondary metabolites owing to several advantageous features like genetic stability, comparable biosynthetic capabilities to the native plant root, and sizable biomass production. Hairy root cultures are reported to produce all major classes of secondary metabolites, such as isoprenoids/or terpenoids, alkaloids, phenolics, and flavonoids. So far, hairy root cultures have been established from a variety of plants providing commercially valuable products, such as artemisinin (Artemisia annua), astragalosides (Astragalus membranaceus), acteoside (Rehmannia glutinosa), centellosides (Centella asiatica), resveratrol (Arachis hypogaea), camptothecin (Camptotheca acuminata), vinblastine, vincristine (Catharanthus roseus), and kutkin, iridoid glycosides (Picrorhiza kurroa). In hairy root cultures, these specialized metabolites are produced via complex network of several distinctive biochemical pathways operating in an integrated manner. However, biochemical pathways and genes involved in production of many phytochemicals have not been completely elucidated. Transcriptome sequencing of hairy root cultures by next-generation sequencing techniques has been proven to be an excellent approach in elucidation of biosynthetic pathways and genes of phytochemical production. Newly emerged next-generation sequencing techniques like Roche/454 and Illumina/Solexa have greatly facilitated sequencing of transcriptome of hairy root cultures. At present, transcriptome sequence datasets of hairy root cultures of only a limited numbers of plants, viz., C. roseus, P. ginseng, A. membranaceus, R. glutinosa, C. asiatica, etc., are available. Thorough analyses of transcriptome sequence datasets of hairy root cultures have unraveled many biosynthetic pathways and genes responsible for the biosynthesis of commercially important phytochemicals. The present chapter provides an up-to-date information of transcriptome sequencing of hairy root cultures of important plants performed by next-generation sequencing techniques.