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

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

SELF-INCOMPATIBILITY IN HAZELNUT SPECIES (CORYLUS AVELLANA L.): EXPRESSION OF SMALL NUCLEOLAR RNAS (SNORNAS) FEMALE INFLUORESCENCE

MASSARDO D.R.*, VENEZIANO A.*, DEL GIUDICE A.*, ALIFANO P.**, SANTANGELO I.***, PICCIRILLO P.****, DEL GIUDICE L.*

* Istituto Internazionale di Genetica e Biofisica–CNR, Via G. Marconi 10, 80125 Napoli

delgiudi@iigbna.iigb.na.cnr.it

** Dipartimento di Biologia, Università di Lecce

*** Regione Campania - Se.S.I.R.C.A., Napoli

**** Istituto Sperimentale per la Frutticoltura, Via Torrino 3, 81100 Caserta

Hazelnut, Corylus avellana L., incompatibility, rRNA, snoRNA

All species of the Corylus genus are monoecious. During flowering, it is possible to observe concurrently distinct male and female influorescences located on the same one-year-old shoot, on the leaf scar axils. Except for some cultivars, the hazelnut is self-incompatible and inter-incompatibility between varieties frequently occurs. Recently studies at molecular level were addressed for the understanding the fertility process which could be useful in the higher quality production of hazelnut. Average world production of unshelled hazelnut amounts to about 700,000 – 800,000 tonnes a year and is mainly concentrate in four countries, namely Turkey, Italy, Spain and United States. These data point out the economic interest of hazelnut plant species particularly for commerce and industry.

As an approach to understanding how self-incompatibility gene is regulated we have identified, by RNA gel mobility shift, a rRNA specific binding activity from female bud soluble extracts of a series of hazelnut cultivars. Competition experiments have put in evidence that specific binding activity associated factors are present in stoicheiometric quantity in comparison to that of rRNAs in the female bud extracts. On the contrary these factors result in scarcely quantity and are not evidenceable both in the pollen and in non-reproductive structures of plant.

Hybridisation-competition experiments have shown that the specific binding activity could be mediated by antisense sequence complementary to rRNA specific regions conserved during evolution. In the last decade the characterisation of a complex family of small nucleolar RNA (snoRNA) containing sequences complementary to wide rRNA regions has been reported. SnoRNA’s function has been related to the methylation processing of ribose specific residues, a post-transcriptional modification common to the eukaryotic rRNAs, useful both for the rRNA processing and for the biogenesis of mature ribosomes.

In the present work we have used agarose gels and sucrose gradients to demonstrate the existence of factor(s) inducing rRNA aggregate formation in female influorescences of hazelnut, a species that show a peculiar floral biology rendering it a biological system particularly attractive for the analysis of female structure differentiation and development. We have biochemical evidence that the factor(s) responsible for rRNA aggregation is associated with a spectacular accumulation of snoRNAs in these reproductive structures. Studies are in progress to verify the involvement of these antisense snoRNA molecules with the incompatibility phenotype in plants.

Acknowledgement: Work was supported by Regione Campania – Se.S.I.R.C.A., special grant “Ricerca sul Nocciolo” and by MIPAF, special grant “Piano Nazionale Biotecnologie Vegetali”.