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Open Access Research article

Solanum torvum responses to the root-knot nematode Meloidogyne incognita

Paolo Bagnaresi1, Tea Sala2, Tiziana Irdani3, Cristina Scotto3, Antonella Lamontanara1, Massimiliano Beretta4, Giuseppe Leonardo Rotino2, Sara Sestili5, Luigi Cattivelli1 and Emidio Sabatini5*

Author Affiliations

1 Consiglio per la Ricerca e la Sperimentazione in Agricoltura, Genomics Research Centre, via S Protaso 302, I-29107, Fiorenzuola d’Arda (PC), Italy

2 Consiglio per la Ricerca e la Sperimentazione in Agricoltura, Unità di Ricerca per l’Orticoltura, Montanaso Lombardo (LO), Italy

3 Consiglio per la Ricerca e la Sperimentazione in Agricoltura, Centro di ricerca per l’agrobiologia e la pedologia, Cascine del Riccio, 50125, Firenze, Italy

4 UNIMORE, Scienze Agrarie e degli Alimenti, Università degli Studi di Modena e Reggio Emilia, via Giovanni Amendola 2, Padiglione Besta, Reggio Emilia 42122, Italy

5 Consiglio per la Ricerca e la Sperimentazione in Agricoltura, Unità di Ricerca per l’Orticoltura, Monsampolo del Tronto, AP, Italy

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BMC Genomics 2013, 14:540  doi:10.1186/1471-2164-14-540

Published: 9 August 2013

Abstract

Background

Solanum torvum Sw is worldwide employed as rootstock for eggplant cultivation because of its vigour and resistance/tolerance to the most serious soil-borne diseases as bacterial, fungal wilts and root-knot nematodes. The little information on Solanum torvum (hereafter Torvum) resistance mechanisms, is mostly attributable to the lack of genomic tools (e.g. dedicated microarray) as well as to the paucity of database information limiting high-throughput expression studies in Torvum.

Results

As a first step towards transcriptome profiling of Torvum inoculated with the nematode M. incognita, we built a Torvum 3’ transcript catalogue. One-quarter of a 454 full run resulted in 205,591 quality-filtered reads. De novo assembly yielded 24,922 contigs and 11,875 singletons. Similarity searches of the S. torvum transcript tags catalogue produced 12,344 annotations. A 30,0000 features custom combimatrix chip was then designed and microarray hybridizations were conducted for both control and 14 dpi (day post inoculation) with Meloidogyne incognita-infected roots samples resulting in 390 differentially expressed genes (DEG). We also tested the chip with samples from the phylogenetically-related nematode-susceptible eggplant species Solanum melongena. An in-silico validation strategy was developed based on assessment of sequence similarity among Torvum probes and eggplant expressed sequences available in public repositories. GO term enrichment analyses with the 390 Torvum DEG revealed enhancement of several processes as chitin catabolism and sesquiterpenoids biosynthesis, while no GO term enrichment was found with eggplant DEG.

The genes identified from S. torvum catalogue, bearing high similarity to known nematode resistance genes, were further investigated in view of their potential role in the nematode resistance mechanism.

Conclusions

By combining 454 pyrosequencing and microarray technology we were able to conduct a cost-effective global transcriptome profiling in a non-model species. In addition, the development of an in silico validation strategy allowed to further extend the use of the custom chip to a related species and to assess by comparison the expression of selected genes without major concerns of artifacts. The expression profiling of S. torvum responses to nematode infection points to sesquiterpenoids and chitinases as major effectors of nematode resistance. The availability of the long sequence tags in S. torvum catalogue will allow precise identification of active nematocide/nematostatic compounds and associated enzymes posing the basis for exploitation of these resistance mechanisms in other species.

Keywords:
Torvum; Nematode resistance; 454 pyrosequencing; Microarray; Heterologous hybridizations