1. ¹Dipartimento di Produzione Vegetale, Università degli Studi di Milano, Milano, Italy
2. ²Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano, Milano, Italy
3. ³Dipartimento di Genetica e Microbiologia, Università degli Studi di Pavia, Pavia, Italy

Correspondence: Dr R Pilu, Dipartimento di Produzione Vegetale, University of Milano, Via celoria 2, Milano 20133, Italy. E-mail: salvatore.pilu@unimi.it

⁴These authors contributed equally to this work.

Received 26 March 2008; Revised 1 July 2008; Accepted 8 August 2008; Published online 10 September 2008.

Abstract

So far, in maize, three classes of mutants involved in phytic acid biosynthesis have been isolated: lpa1, lpa2 and lpa3. In 2007, a gene tagging experiment performed by Shi et al. found that mutations in ZmMRP4 (multidrug resistance-associated proteins 4) gene cause lpa1 phenotype. In previous studies, we isolated and described a single recessive lpa mutation (originally named lpa241), which was allelic to the lpa1-1 mutant, and was consequently renamed lpa1-241. It showed a decrease in the expression of the myo-inositol (Ins)-3-phosphate synthase gene (mips1S). In this study, we present genetic and molecular analyses of the lpa1-241 mutation that indicate an epigenetic origin of this trait, that is, a paramutagenic interaction that results in meiotically heritable changes in ZmMRP4 gene expression, causing a strong pleiotropic effect on the whole plant. The use of a 5-Azacytidine treatment provided data suggesting an association between gene methylation and the lpa1-241 phenotype. To our knowledge, this is the first report of a paramutagenic activity not involving flavonoid biosynthesis in maize, but regarding a key enzyme of an important metabolic pathway in plants.