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Open Access Research article

Characterization of the glutathione S-transferase gene family through ESTs and expression analyses within common and pigmented cultivars of Citrus sinensis (L.) Osbeck

Concetta Licciardello1, Nunzio D’Agostino2, Alessandra Traini4, Giuseppe Reforgiato Recupero1, Luigi Frusciante3 and Maria Luisa Chiusano3*

Author Affiliations

1 Consiglio per la Ricerca e la sperimentazione in Agricoltura - Centro di ricerca per l'Agrumicoltura e le Colture Mediterranee (CRA-ACM), Corso Savoia 190, 95024 Acireale, Catania, Italy

2 Consiglio per la Ricerca e la sperimentazione in Agricoltura - Centro di ricerca per l'Orticoltura (CRA-ORT), via Cavalleggeri 25, 84098 Pontecagnano, Salerno, Italy

3 Dipartimento di Agraria, Università degli Studi di Napoli “Federico II”, Via Università, 100, 80055 Portici, Naples, Italy

4 Wellcome Trust Genome Campus, Hinxton, Cambridgeshire CB10 1SA, UK

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BMC Plant Biology 2014, 14:39  doi:10.1186/1471-2229-14-39

Published: 3 February 2014

Abstract

Background

Glutathione S-transferases (GSTs) represent a ubiquitous gene family encoding detoxification enzymes able to recognize reactive electrophilic xenobiotic molecules as well as compounds of endogenous origin. Anthocyanin pigments require GSTs for their transport into the vacuole since their cytoplasmic retention is toxic to the cell. Anthocyanin accumulation in Citrus sinensis (L.) Osbeck fruit flesh determines different phenotypes affecting the typical pigmentation of Sicilian blood oranges. In this paper we describe: i) the characterization of the GST gene family in C. sinensis through a systematic EST analysis; ii) the validation of the EST assembly by exploiting the genome sequences of C. sinensis and C. clementina and their genome annotations; iii) GST gene expression profiling in six tissues/organs and in two different sweet orange cultivars, Cadenera (common) and Moro (pigmented).

Results

We identified 61 GST transcripts, described the full- or partial-length nature of the sequences and assigned to each sequence the GST class membership exploiting a comparative approach and the classification scheme proposed for plant species. A total of 23 full-length sequences were defined. Fifty-four of the 61 transcripts were successfully aligned to the C. sinensis and C. clementina genomes. Tissue specific expression profiling demonstrated that the expression of some GST transcripts was 'tissue-affected' and cultivar specific. A comparative analysis of C. sinensis GSTs with those from other plant species was also considered. Data from the current analysis are accessible at http://biosrv.cab.unina.it/citrusGST/ webcite, with the aim to provide a reference resource for C. sinensis GSTs.

Conclusions

This study aimed at the characterization of the GST gene family in C. sinensis. Based on expression patterns from two different cultivars and on sequence-comparative analyses, we also highlighted that two sequences, a Phi class GST and a Mapeg class GST, could be involved in the conjugation of anthocyanin pigments and in their transport into the vacuole, specifically in fruit flesh of the pigmented cultivar.

Keywords:
Sweet orange; GST; Expressed sequence tag; Gene family; Anthocyanin vacuolarization