title: Endophytic actinobacteria: Diversity, secondary metabolism and mechanisms to unsilence biosynthetic gene clusters.
abstract: Endophytic actinobacteria, which reside in the inner tissues of host plants, are gaining serious attention due to their capacity to produce a plethora of secondary metabolites (e.g. antibiotics) possessing a wide variety of biological activity with diverse functions. This review encompasses the recent reports on endophytic actinobacterial species diversity, in planta habitats and mechanisms underlying their mode of entry into plants. Besides, their metabolic potential, novel bioactive compounds they produce and mechanisms to unravel their hidden metabolic repertoire by activation of cryptic or silent biosynthetic gene clusters (BGCs) for eliciting novel secondary metabolite production are discussed. The study also reviews the classical conservative techniques (chemical/biological/physical elicitation, co-culturing) as well as modern microbiology tools (e.g. next generation sequencing) that are being gainfully employed to uncover the vast hidden scaffolds for novel secondary metabolites produced by these endophytes, which would subsequently herald a revolution in drug engineering. The potential role of these endophytes in the agro-environment as promising biological candidates for inhibition of phytopathogens and the way forward to thoroughly exploit this unique microbial community by inducing expression of cryptic BGCs for encoding unseen products with novel therapeutic properties are also discussed.
authors.affiliation: a ICAR-Indian Institute of Spices Research , Kozhikode, Kerala , India.
authors.forename: Raghavan
authors.initials: R
authors.lastname: Dinesh
authors.affiliation: a ICAR-Indian Institute of Spices Research , Kozhikode, Kerala , India.
authors.forename: Veeraraghavan
authors.initials: V
authors.lastname: Srinivasan
authors.affiliation: a ICAR-Indian Institute of Spices Research , Kozhikode, Kerala , India.
authors.forename: Sheeja
authors.initials: S
authors.lastname: T E
authors.affiliation: a ICAR-Indian Institute of Spices Research , Kozhikode, Kerala , India.
authors.forename: Muthuswamy
authors.initials: M
authors.lastname: Anandaraj
authors.affiliation: a ICAR-Indian Institute of Spices Research , Kozhikode, Kerala , India.
authors.forename: Hamza
authors.initials: H
authors.lastname: Srambikkal
mesh_terms: D039903:Actinobacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D001688:Biological Products / Q000494:pharmacology*; D055808:Drug Discovery / Q000379:methods; D060026:Endophytes / Q000254:growth & development / Q000378:metabolism*; D059014:High-Throughput Nucleotide Sequencing; D005810:Multigene Family / Q000235:genetics; D010944:Plants / Q000382:microbiology; D064210:Secondary Metabolism / Q000502:physiology*
chemical_list: D001688:Biological Products
keywords: Actinobacteria; biosynthetic gene clusters; endophytes; next generation sequencing; secondary metabolites