Plant Science 130 (1997) 51–62 Effects of a triazolic fungicide on maize plant metabolism: modifications of transcript abundance in resistance-related pathways Angela Ronchi a , Gandolfina Farina b , Franco Gozzo c , Chiara Tonelli a, * a Dipartimento di Genetica e di Biologia dei microrganismi, Via Celoria 26, 20133 Milano, Italy b Istituto di Patologia Vegetale, Uniersita ` di Milano, ia Celoria 2, 20133 Milano, Italy c Dipartimento di Scienze Molecolari Agroalimentari, ia Celoria 2, 20133 Milano, Italy Received 12 February 1997; received in revised form 13 August 1997; accepted 13 August 1997 Abstract Using a molecular approach, the effects of tetraconazole (TC), a triazolic inhibitor of P-450-based enzymes, has been investigated in maize, focusing on the resistance-related biosynthetic pathways involving one or more microso- mial P-450 mono-oxigenases, putative secondary targets of the fungicide. Several observations were made. First, TC affected the phenylpropanoid-flavonoid biosynthesis, increasing the anthocyanin content and the mRNA abundance of the genes involved in the later steps of the pathway (A1 and C2 ), while the expression of another gene, PAL, decreased in the roots. Second, the activity of a hydroxyproline-rich glycoprotein gene involved in root cell wall structures was enhanced. Finally, maize seedlings acquired increased resistance to drought, which corresponded with modified levels of abscissic acid (ABA) and the overexpression of an ABA regulated gene. Taken together, these results suggest that TC act as a potential activator of plant defence-responses to both abiotic and biotic challenges and represents a powerful tool for elucidating the regulatory interconnections between different biosynthetic pathways. © 1997 Elsevier Science Ireland Ltd. Keywords: Triazoles; Anthocyanins; Flavonoid gene expression; Abscissic acid; Plant stress 1. Introduction Triazole derivatives have been used in pharma- cology and in agriculture as fungicides. In fungi, they are inhibitors of the cytochrome P450-depen- dent 14 -demethylase, an enzyme in the sterol * Corresponding author. Tel.: +39 2 26605210; fax: +39 2 2664551; e-mail: tonelli@imiucca.csi.unimi.it 0168-9452/97/$17.00 © 1997 Elsevier Science Ireland Ltd. All rights reserved. PII S0168-9452(97)00190-8