Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Poster Abstract - 1.43

DIFFERENTIAL GENE EXPRESSION IN CITRANGE TROYER OVEREXPRESSING ARABIDOPSIS PHYTOCHROME B GENE, AS DETERMINED BY REAL TIME PCR

P. LATINI*, G. DISTEFANO**, A. CONTINELLA**, S. LA MALFA**, M.C. INTRIERI*, D. ZINIU**, E. RUGINI*, A. GENTILE**, R. MULEO*

*) Dipartimento di Produzione Vegetale, Università della Tuscia, Viterbo, Italy

**) Dipartimento di OrtoFloroArboricoltura e Tecnologie Agroalimentari sez. Arboricoltura, Università degli Studi di Catania, Italy

PhyB, Quantitative RT-PCR, Light qualities, gene expression

Light is an important environmental cue, which regulates plant development from seed germination up to flowering and fruit formation. Many genes are under control of light qualities, through the signal transduction of some classes of photoreceptors like the family of Phytochrome, Cryptochrome, UV-receptor and Phototropins. Among them, phytochrome family is the best characterized receptor. In particular, phytochrome B (PHYB) is the most important activated phytochrome under light conditions. In some plants the overexpression of alien phyB gene induces strong modification in gene expression and in morphology, i.e. decrease in stem elongation and in chlorophyll content, increase in branching and delay in senescence.

In this study, genetically transformed citrange Troyer [Citrus sinensis (L.) Osb. x Poncirus trifoliata (L.) Raf.9] overexpressing Arabidopsis phyB gene have been used to investigate the regolative role on the transcription of target genes linked to photosynthetic activity and light signal transduction itself: cab, rbcs, psbA, phyB. Leaves were sampled for molecular analyses from wild type and overeexpressing plants after their exposition to red light. Real Time quantitative RT-PCR (LightCycler, Roche), using SYBR Green I dye method, was performed to quantify the amount of transcripted target genes. Ribosomal 18s genes (18s) were used as an internal control (housekeeping gene) for the normalization of the results.

Results showed a strong reduction in the amount of transcripts of rbcs and cab genes (ranging for 40 to 70%) in plants overexpressing phyB as compared to wild type plants. The other genes studied did not show significant variation of expression levels, excepted for phyB gene. Transgenic plants showed a higher CO₂ exchange rate (CER) compared to that of wild type ones, especially during midday hours.

Moreover, morphological traits seem also to be affected from the transferred DNA, probably, by the alteration of the phyB signal transduction regulating morphogenic events. We speculated that overexpressed phyB may alter the signalling cascade playing a pivotal role in the interaction between PHYB and G-protein and /or PIF3.