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Open Access Research article

Functional genomics of a generalist parasitic plant: Laser microdissection of host-parasite interface reveals host-specific patterns of parasite gene expression

Loren A Honaas1, Eric K Wafula2, Zhenzhen Yang1, Joshua P Der12, Norman J Wickett128, Naomi S Altman3, Christopher G Taylor4, John I Yoder5, Michael P Timko6, James H Westwood7 and Claude W dePamphilis12*

Author affiliations

1 Intercollege Graduate Program in Plant Biology, Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA

2 Department of Biology and Institute of Molecular Evolutionary Genetics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA

3 Department of Statistics and Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA

4 Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH, 44691, USA

5 Department of Plant Sciences, University of California, Davis, Davis, California, 95616, USA

6 Department of Biology, University of Virginia, Charlottesville, VA, 22904, USA

7 Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA

8 Present address: Chicago Botanic Garden, Glencoe, IL, 60022, USA

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Citation and License

BMC Plant Biology 2013, 13:9  doi:10.1186/1471-2229-13-9

Published: 9 January 2013

Abstract

Background

Orobanchaceae is the only plant family with members representing the full range of parasitic lifestyles plus a free-living lineage sister to all parasitic lineages, Lindenbergia. A generalist member of this family, and an important parasitic plant model, Triphysaria versicolor regularly feeds upon a wide range of host plants. Here, we compare de novo assembled transcriptomes generated from laser micro-dissected tissues at the host-parasite interface to uncover details of the largely uncharacterized interaction between parasitic plants and their hosts.

Results

The interaction of Triphysaria with the distantly related hosts Zea mays and Medicago truncatula reveals dramatic host-specific gene expression patterns. Relative to above ground tissues, gene families are disproportionally represented at the interface including enrichment for transcription factors and genes of unknown function. Quantitative Real-Time PCR of a T. versicolor β-expansin shows strong differential (120x) upregulation in response to the monocot host Z. mays; a result that is concordant with our read count estimates. Pathogenesis-related proteins, other cell wall modifying enzymes, and orthologs of genes with unknown function (annotated as such in sequenced plant genomes) are among the parasite genes highly expressed by T. versicolor at the parasite-host interface.

Conclusions

Laser capture microdissection makes it possible to sample the small region of cells at the epicenter of parasite host interactions. The results of our analysis suggest that T. versicolor’s generalist strategy involves a reliance on overlapping but distinct gene sets, depending upon the host plant it is parasitizing. The massive upregulation of a T. versicolor β-expansin is suggestive of a mechanism for parasite success on grass hosts. In this preliminary study of the interface transcriptomes, we have shown that T. versicolor, and the Orobanchaceae in general, provide excellent opportunities for the characterization of plant genes with unknown functions.

Keywords:
Parasitic plant; RNA-Seq; Illumina; De novo assembly; Transcriptome; Laser microdissection; Expansin; Generalist parasite; Orobanchaceae; Triphysaria; Maize; Medicago; Burkholderia