title: Involvement of abscisic acid and salicylic acid in signal cascade regulating bacterial endophyte-induced volatile oil biosynthesis in plantlets of Atractylodes lancea.
abstract: The enormous biological diversity of endophytes, coupled with their potential to enhance the production of bioactive metabolites in plants, has driven research efforts focusing on endophytes. However, limited information is available on the impacts of bacterial endophytes on plant secondary metabolism and signaling pathways involved. This work showed that an endophytic Acinetobacter sp. ALEB16, capable of activating accumulation of plant volatile oils, also induced abscisic acid (ABA) and salicylic acid (SA) production in Atractylodes lancea. Pre-treatment of plantlets with biosynthetic inhibitors of ABA or SA blocked the bacterium-induced volatile production. ABA inhibitors suppressed not only the bacterium-induced volatile accumulation but also the induced ABA and SA generation; nevertheless, SA inhibitors did not significantly inhibit the induced ABA biosynthesis, implying that SA acted downstream of ABA production. These results were confirmed by observations that exogenous ABA and SA reversed the inhibition of bacterium-induced volatile accumulation by inhibitors. Transcriptional activities of genes in sesquiterpenoid biosynthesis also increased significantly with bacterium, ABA and SA treatments. Mevalonate pathway proved to be the main source of isopentenyldiphosphate for bacterium-induced sesquiterpenoids, as assessed in experiments using specific terpene biosynthesis inhibitors. These results suggest that Acinetobacter sp. acts as an endophytic elicitor to stimulate volatile biosynthesis of A. lancea via an ABA/SA-dependent pathway, thereby yielding additional insight into the interconnection between ABA and SA in biosynthesis-related signaling pathways.
authors.affiliation: Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, 210023, China.
authors.forename: Xiao-Mi
authors.initials: XM
authors.lastname: Wang
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
authors.forename: Cheng-Gang
authors.initials: CG
authors.lastname: Ren
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Wang
authors.forename: Jin-Yan
authors.initials: JY
authors.lastname: Wang
authors.forename: Chuan-Chao
authors.initials: CC
authors.lastname: Dai
mesh_terms: D000040:Abscisic Acid / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000150:Acinetobacter / Q000254:growth & development / Q000502:physiology*; D031174:Atractylodes / Q000737:chemistry / Q000382:microbiology / Q000502:physiology*; D053898:Biosynthetic Pathways; D060026:Endophytes; D045782:Hemiterpenes / Q000378:metabolism; D009822:Oils, Volatile / Q000302:isolation & purification / Q000378:metabolism*; D009943:Organophosphorus Compounds / Q000378:metabolism; D010937:Plant Growth Regulators / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010938:Plant Oils / Q000302:isolation & purification / Q000378:metabolism*; D020156:Salicylic Acid / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction; D013559:Symbiosis
chemical_list: D045782:Hemiterpenes; D009822:Oils, Volatile; D009943:Organophosphorus Compounds; D010937:Plant Growth Regulators; D010938:Plant Oils; C004809:isopentenyl pyrophosphate; D000040:Abscisic Acid; D020156:Salicylic Acid