Abstract
Piriformospora indica, an endophytic fungus of Sebacinales, colonizes the roots of a wide range of host plants and establishes various benefits for the plants. In this work, we describe miRNAs which are upregulated in Oncidium orchid roots after colonization by the fungus. Growth promotion and vigorous root development were observed in Oncidium hybrid orchid, while seedlings were colonized by P. indica. We performed a genome-wide expression profiling of small RNAs in Oncidium orchid roots either colonized or not-colonized by P. indica. After sequencing, 24,570,250 and 24744,141 clean reads were obtained from two libraries. 13,736 from 17,036,953 unique sequences showed homology to either 86 miRNA families described in 41 plant species, or to 46 potential novel miRNAs, or to 51 corresponding miRNA precursors. The predicted target genes of these miRNAs are mainly involved in auxin signal perception and transduction, transcription, development and plant defense. The expression analysis of miRNAs and target genes demonstrated the regulatory functions they may participate in. This study revealed that growth stimulation of the Oncidium orchid after colonization by P. indica includes an intricate network of miRNAs and their targets. The symbiotic function of P. indica on Oncidium orchid resembles previous findings on Chinese cabbage. This is the first study on growth regulation and development of Oncidium orchid by miRNAs induced by the symbiotic fungus P. indica.
Highlights
Piriformospora indica, a root-colonizing endophyte with a broad host range, is intensively studied due to its diverse beneficial effects on the performance of both monocot and eudicot plants
The results indicated that most of the predicted target genes of the conserved micro RNAs (miRNAs) were consistent with the results using the O. sativa and A. thaliana mRNA databases, but some miRNAs such as mir528, which was only detected in monocotyledons, were predicted to target different genes in each of the three databases
We report on the miRNA profiling of Oncidium orchid after colonization by P. indica
Summary
Piriformospora indica, a root-colonizing endophyte with a broad host range, is intensively studied due to its diverse beneficial effects on the performance of both monocot and eudicot plants. Since the fungus can be cultivated without any host, it became a model organism to study symbiotic root interactions [3]. Proteomics and transcriptomics were employed to study the interaction of P. indica with Arabidopsis thaliana and barley, and stage-specific up- or downregulated proteins and genes involved in phytohormone metabolism [11,12] and membrane protein synthesis [13] were detected. P. indica promotes growth of Chinese cabbage (Brassica campestris subsp.chinensis). Analysis of a double-subtracted EST cDNA library identified genes associated with auxin biosynthesis and signaling indicating that this phytohormone might be crucial in the Chinese cabbage/P. indica symbiosis [14]
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