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

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Oral Communication Abstract - S2m

IDENTIFICATION OF DIFFERENTIALLY EXPRESSED GENES INVOLVED IN HORDEUM VULGARE-PYRENOPHORA GRAMINEA INTERACTION

V. BONARDI*, A. HAEGI**, G. VALÈ***, E. DALLAGLIO***, A. PORTA-PUGLIA**, M. DELLEDONNE*

*) Università degli Studi di Verona, Strada Le Grazie 15, Cà Vignal 1, 37134 Verona

**) Istituto Sperimentale per la Patologia vegetale, via C.G. Bertero 22, 00156 Roma

***) Istituto Sperimentale per la Cerealicoltura , via S. Protaso 302, 29017 Fiorenzuola d’Arda, Piacenza

AFLP-TP, Hordeum vulgare, Pyrenophora graminea, barley leaf stripe

Pyrenophora graminea is the agent of barley leaf stripe, a disease occuring in almost all barley growing areas, characterized by chlorotic stripes that gradually extend to the full length of the leaf and finally become necrotic. The fungus is unable to cause any secondary infection through leaf-to-leaf transmission, so it could be considered a true seed-borne pathogen. The mechanisms of pathogenicity/resistance of barley-Pyrenophora graminea interaction are not well understood. A variety of sources of resistance to the fungus have been reported but these are often contradictory. Moreover, mechanisms of resistance controlled by one, two, three or more genes have been proposed.

Understanding the molecular mechanisms underlying plant-pathogen interaction will clearly benefit the agricultural industry, leading to informed strategies for reducing crop losses caused by the disease. As a matter of fact the fungus is supposed to establish an intimate association with the plant and such interaction involves complex recognition events between the two partners, leading to signaling cascades and regulation of countless genes required for, or associated with, the interaction. Identifying the battery of genes modulated during the infection will help, from one hand, to develop a detailed picture about seed’s pathology and pathogenetic variability in fungi in order to restrain the disease, and, from the other, to get a better knowledge on the interaction of Pyrenophora graminea with barley in order to develop molecular markers useful in the selection of resistant plants.

AFLP-TP technique is a sensitive and reproducible fragment-based technology that has a number of advantages over other methods for genome-wide expression analysis: it does not require prior sequence information, it allows the identification of novel genes, and it provides quantitative expression profiles.

To elucidate the nature of the molecular “conversation” between barley and Pyrenophora graminea, the AFLP-TP patterns of the fungus itself and of resistant and susceptible cultivars, alone and in their interaction with the fungus, have been compared. The interaction has been studied at three times of infection (7, 10 and 15 days). From the analysis of the entire transcriptional profile, 1,162 genes were found to be differentially regulated; in particular 76.7 % of those were up-regulated and the remaining 23.3 % down-regulated with respect to the uninfected susceptible cultivar. A comprehensive collection of infection-modulated genes has been built. Hierarchical clustering of the expression profiles resulted in a variety of groups which may reveal a putative functional classification of the transcript tags.

500 AFLP fragments have been already cloned in a T-vector and they are being sequenced in order to get a clear picture of the dynamic exchange of signals that occurs between barley and Pyrenophora graminea to result in resistance or susceptibility.