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

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Poster Abstract - 5.08

EXPRESSION IN TOBACCO OF TOMATO PROSYSTEMIN ACTIVATES GENES INVOLVED IN DIRECT AND INDIRECT PLANT DEFENCE RESPONSE

TORTIGLIONE C.*, MAZZITELLI L.**, GUERRIERI E.***, RAO R.**

*) Istituto per il Miglioramento Genetico delle Piante da Orto e da Fiore, CNR, Portici,

**) Dipartimento di Scienze del Suolo, della pianta e dell’ Ambiente, Università di Napoli, Federico II, Portici

***) Istituto per la Protezione delle Piante, CNR, Portici

lipoxygenase, proteinase inhibitor, attractiveness, A. ervi

Plants respond to herbivore attack with a dramatic functional reorganization that involves the activation of direct and indirect defences. These defences, include the local and systemic production of molecules targeting directly gut membranes or inhibiting gut proteases and the production of volatiles attracting insects and mites that prey upon or parasitize herbivores. In tomato the molecule responsible of the wound induced signalling transduction pathway is systemin, a18-amino acid long peptide. This peptide induces the activation of genes directly involved in the plant defence towards herbivorous insects through the jasmonate dependent-pathway. Jasmonates are active both inside and outside the plants. In fact volatile jasmonates influence insect behaviour playing a role in defence by attracting herbivore predators and parasitoids.

Genes coding for systemin have been identified in potato, nightshade and pepper, but not in tobacco, a more distantly related solanacea. Tobacco plants were found unable to responde to exogenously supplied tomato systemin, supporting the existance of a different polypeptide involved in the wound signalling. Recently, in this species two molecules involved in the systemic wound signal transduction have been isolated and they resulted structurally different from other systemins and sharing no homologies to them. Herein, we report that tomato prosystemin driven by a constitutive promoter when stably expressed in tobacco plants is able to induce constitutively the synthesis of lipoxygenase (LOX), the first enzyme of the octadecanoid pathway, and proteinase inhibitor (PI-II), a downstream gene directly involved in insect defence response. Furthermore transgenic tobacco plants exert attraction on A. ervi, an insect parassitoid, thus supporting evidence that also the indirect defence response is activated by the expression of prosystemin gene. These data suggest the presence in tobacco of the protease activities necessary to properly process the tomato prosystemin precursor and activate wound signal transduction pathway.