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 - 1.42

MUTANT GENES RELATED WITH ETHYLENE PERCEPTION AND SYNTHESIS (Nr, rin, nor) MODULATE THE DEGREE OF AUTONECROSES IN THE TOMATO (LYCOPERSICON ESCULENTUM MILL.) "LESION MIMIC" MUTANT V20368

V. FONZO*, P. MOSCONI*, R. CACCIA*, E. SANTANGELO**, G.P. SORESSI*

*) University of Tuscia, DABAC, via S.C. de Lellis s.n.c., 01100 Viterbo

**) Consorzio Agrital Ricerche, viale dell'Industria 24, 00057 Maccarese (Roma)

ethylene, lesion mimic, PCD, tomato

A distinctive trait of plant-pathogen incompatible reaction is the hypersensitive reaction (HR), a mechanism of programmed cell death (PCD) used by the plant in order to limit the pathogen spreading. The ethylene hormone is one of the putative regulators of PCD in some physiological processes (He et al., 1996; Orzaez and Granell, 1997; Young and Gallie, 2000; De Jong et al., 2002) and its role as signal molecule (with salicilic and jasmonic acid) is well known (Lund et al., 1998; O’Donnell et al., 2001; Gu et al., 2000).

For the comprehension of mechanisms activated during the PCD, an important tool is the study of the “lesion-mimic” mutants, mimicking forms of cell death resembling those triggered during the plant-pathogen interaction. In tomato an "autonecrotic" mutant was described first by Rick and Butler (1956) and recently studied by Kruger et al. (2002). The necrotic lesions are triggered by high temperature and luminosity on 6 week old plants with an acropetal direction and are caused by the interaction between the Cf-2 resistance gene (introduced from L. pimpinellifolium) and a second gene (Rcr3^esc) belonging to L. esculentum and encoding for a cystein protease.

In a new tomato autonecrotic mutant (line V20368), previously characterised from a genetic, biochemical and molecular point of view, the role of ethylene in the modulation of the necroses formation was investigated, by crossing the autonecrotic line with the tomato mutants for perception (Nr) and synthesis (nor, rin) of ethylene.

Parental lines (V20368, Nr, rin and nor) and the F₁ hybrids between V20368 and the ethylene mutants were grown in tunnel during environmental conditions leading to the autonecroses. The phenotypic manifestation of necroses was evaluated and the ethylene (by gas chromatograph) and cell integrity (by ion leakage) measured on the basal, central and apical leaves when the necrotic spots appeared on the basal ones.

From the data emerged differences in terms of time of appearing, number and diameter of lesions, in relation to the presence of Nr, rin and nor genes. The necrose evolution seem affected by the ethylene reduction due to the nor and rin genes, but not by its perception due to the Nr gene. In fact, the F₁ between V20368 and rin or nor appeared less necrotic, while the F₁ with Nr exhibited earlier and more severe necrotic lesions. A maternal effect was also observed.