ABSTRACT
ABC transporters (ATP-binding cassette transporters) are a family of trans-membrane transport proteins, which are ubiquitous in prokaryotes and eukaryotes. They are functionallyinvolved in the transport and accumulation of plant secondary metabolites, phytohormone transport, lipid metabolism, exogenous toxins detoxification, plant disease and other aspects. Based on the genome and transcriptome data of Dendrobium officinale, 88ABC transporters were preliminarily identified in D. officinale and their functions and subcellular localization were predicted. These proteins are divided into seven subfamilies, ABCA-ABCI, including 4 ABCA, 19 ABCB, 12 ABCC, 3ABCD, 9 ABCF, 37ABCG and 4 ABCI, which are mainly located in plasma membrane, vacuole and Golgi apparatus. Comparative transcriptomic analysis of ABC protein expression profile between asymbiotic and symbiotic germination of D. officinale show that some members of ABCB and ABCG proteins are highly expressed during seed germination inoculated fungi. qPCR validated that 2 ABCB11 and 2 ABCG-PDR are significantly up-regulated in symbiotic assay compared to asymbiotic germination (fold change ≥ 10.0). These proteins are mainly involved in abscisic acid and auxin transport, suggesting that these proteins play an important role in the germination of D. officinale seed and in the interaction with microorganisms.
ABSTRACT
OBJECTIVE: To investigate differential gene expression profiling of symbiotic germinated seeds of Dendrobium officinale. METHODS: cDNAs from 5-week symbiotic germinated seeds and 5-week aseptic cultivated seeds, taken as the tester and driver respectively, were used to construct a suppressive subtractive hybridization (SSH) cDNA library. RESULTS: By sequencing positive clones and BLASTx analysis against GenBank database, 100 expressed sequence tags (EST) homologous to plant known genes were obtained. Functional annotation revealed that they were grouped into serials of cellular processes including cell and chromosome structure, RNA synthesis, signal transduction, energy metabolism, protein synthesis and degradation, and cell defense, etc. Real-time quantitative RT-PCR analyses showed that the five randomly selected genes were all up-regulated in symbiotic germinated seeds. CONCLUSION: The symbiotic seed germination of D. officinale is involved in multiple pathways, and the results of this study will lay a foundation for further molecular elucidation of seed germination in Orchidaceae.