Variability of PSPAL1 (phenylalanine ammonia-lyase gene-1) proximal promoter sequence and expression in pea challenged with Mycosphaerella pinodes

Abstract

Part of the PSPAL1 gene (corresponding to the proximal promoter, exon 1 and intron) from eight pea varieties was sequenced and compared to the published sequence of PSPAL1 gene from Midoriusui cultivar (GenBank: D10002.1). The sequences showed a very high level of identity (96–99%), except in five varieties there occurred a motif TTATTACAAAATATTA close to the Goldberg-Hogness (TATA) box, and it was not detected in the other four varieties, including Midoriusui. Plants of eight pea varieties were subjected to controlled infection with Mycosphaerella pinodes and the disease index was determined (it ranged from 5.2 to 42.3%). The PSPAL1 gene of the most resistant cultivar (Walor) contained the above-mentioned motif and that of the most susceptible (Polar) did not. However, the relationship was not clear in varieties with intermediate levels of resistance. In four varieties (Walor, Ezop, Ramrod and Polar) the expression level of PSPAL1 gene in leaves was analysed (1, 3, 6, 9, 12 and 15 h post inoculation) and it showed a weak negative correlation with disease severity (R= – 0.53). The activation of PSPAL1 gene occurred not only in infected pea leaves but also in stems and – to a much lower degree – in roots (with the relative level of PSPAL1 transcripts amounting to 0.15 in roots and 38.75 in leaves), indicating some kind of signal transmission beyond the infected plant tissues.