Open Access Research article

Organogenic nodule development in hop (Humulus lupulus L.): Transcript and metabolic responses

Ana M Fortes1*, Filipa Santos15, Young H Choi2, Marta S Silva3, Andreia Figueiredo1, Lisete Sousa4, Fernando Pessoa1, Bartolomeu A Santos16, Mónica Sebastiana1, Klaus Palme5, Rui Malhó1, Rob Verpoorte2 and Maria S Pais1

Author Affiliations

1 ICAT, FCUL, University of Lisbon, Campo Grande, 1749-016 Lisbon, Portugal

2 Division of Pharmacognosy, Section Metabolomics, Institute Biology Leiden, Leiden, the Netherlands

3 Department of Chemistry and Biochemistry, FCUL, Lisbon, Portugal

4 Department of Statistics and Operational Research, CEAUL (Centro de Estatística e Aplicações da UL), FCUL, Lisbon, Portugal

5 Institute for Biology II/Botany, Albert-Ludwig's University, Freiburg, Germany

6 Dep. Micologia, University Federal de Pernambuco, Av. Prof. Nelson Chaves s/n, Cidade University, 50670-420, Recife, PE, Brazil

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BMC Genomics 2008, 9:445  doi:10.1186/1471-2164-9-445

Published: 29 September 2008

Abstract

Background

Hop (Humulus lupulus L.) is an economically important plant forming organogenic nodules which can be used for genetic transformation and micropropagation. We are interested in the mechanisms underlying reprogramming of cells through stress and hormone treatments.

Results

An integrated molecular and metabolomic approach was used to investigate global gene expression and metabolic responses during development of hop's organogenic nodules.

Transcript profiling using a 3,324-cDNA clone array revealed differential regulation of 133 unigenes, classified into 11 functional categories. Several pathways seem to be determinant in organogenic nodule formation, namely defense and stress response, sugar and lipid metabolism, synthesis of secondary metabolites and hormone signaling. Metabolic profiling using 1H NMR spectroscopy associated to two-dimensional techniques showed the importance of metabolites related to oxidative stress response, lipid and sugar metabolism and secondary metabolism in organogenic nodule formation.

Conclusion

The expression profile of genes pivotal for energy metabolism, together with metabolites profile, suggested that these morphogenic structures gain energy through a heterotrophic, transport-dependent and sugar-degrading anaerobic metabolism. Polyamines and auxins are likely to be involved in the regulation of expression of many genes related to organogenic nodule formation. These results represent substantial progress toward a better understanding of this complex developmental program and reveal novel information regarding morphogenesis in plants.