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

THE BARLEY "LEMMA SYSTEM": A MODEL FOR LEAF DEVELOPMENT STUDIES

POZZI C.*, ROSSINI L.**, BARALE F.**, VANDONI D.**, DECIMO I.**, ROIG C.***, FACCIOLI P.****, SANTI L.***, SALAMINI F.*^,**^,***

* Fondazione Parco Tecnologico Padano, Lodi, c/o 2

carlo.pozzi@unimi.it

** Dipartimento di Produzione Vegetale, Via Celoria 2, 20133 Milano

*** Max Planck Institute for Plant Breeding Reasearch, Carl-vopn-Linné Weg 10, 50829 Köln, Germany

**** Istituto Sperimentale per la Cerealicoltura, V San Protaso 302, 29017 Fiorenzuola d’Arda (PC)

barley, developmental mutants, homeotic genes, linkage mapping

A large variety of developmental mutants affecting both vegetative and reproductive organs of barley (Hordeum vulgare L.) have been collected at the Department of Plant Breeding and Yield Physiology of the Max-Planck Institute in Cologne. In a functional genomics approach, mutants have been morphologically characterized and mapped on the established high-density molecular linkage map of barley. This step is followed by fine mapping of the loci and attempts at map-based cloning. The mapping strategy is based on integration of the molecular linkage map with the position of mutant loci and isolated genes. At present, 35 barley mutants and 7 genes have been mapped using this approach. In parallel, homeotic gene families are characterized and mapped. The attention of our group was attracted to Hooded (K), a dominant mutant which exhibits a distinctive perturbation of the interface between lemma and awn resulting in the formation of an extra flower arranged in inverse polarity compared to the barley floret. Molecular analyses revealed that the Hooded phenotype is due to a 305bp duplication in intron IV of the homebox gene Bkn3. Sequence analysis of all available K alleles and a variety of wild type barley accessions demonstrated that the mutation occurred only once in evolution. Since the duplication causes ectopic expression of Bkn3, functional activities of the 305 bp sequence have been tested in a yeast one-hybrid system, in order to identify proteins interacting with the 305 bp sequence. In parallel, a mutagenesis program with the Hooded genotype led to the isolation of 5 different suppressor-of-Hooded loci. These are being mapped using a modification of the above cited strategy. Other classes of lemma mutations studied are the 5 recessive calcaroides loci and the leafy lemma mutant. The latter provides evidence for the lemma as a modified leaf-like organ. Our group is also concentrating on the isolation and characterization of barley homologues of genes know to negative regulate Knox homeobox genes in other species. This project led to the isolation of the barley rough sheath 2 (Brs2) homologue. In addition we are characterizing Mutations producing branching or phytomeric additions and the positional cloning of the gene responsible for the branched barley mutation is under way. A BAC library is available for the isolation of the contig spanning the branched region.