Ustilago maydis induced accumulation of putrescine in maize leaves

Abstract

Polyamines are implicated in the regulation of many processes in the plant cell, including functioning of ion channels, DNA replication, gene transcription, mRNA translation, cell proliferation and programmed cell death. Plant polyamines occur either in free form, covalently bound to proteins, or conjugated to hydroxycinnamic acids forming phenol amides. Ustilago maydis is a dimorphic and biotrophic pathogenic fungus responsible for common smut or “huitlacoche” in maize; and it is considered an excellent model for the study of plant-pathogen interactions. Recently, we reported alterations in polyamine metabolism of maize tumors induced on leaf blades by Ustilago maydis infection. Our data revealed a striking increase in maize polyamine biosynthesis, mainly free and conjugated putrescine in the tumors and in the green plant tissue surrounding the tumor. In this addendum, we describe that changes in polyamine metabolism take place even in earlier stages of maize plant infection with Ustilago maydis.

Keywords: Ustilago maydis; Zea mays; early stages; polyamines.

Figure 1

Determination of free and conjugated polyamine contents in 8 and 11 d-old maize plants infected (2 and 5 dpi) or not with U. maydis. (A and D) Put; (B and E) Spd; and (C and F) Spm. C, control plant; W, wounded plant; Chl, chlorosis; I, inoculated plant. Data are mean ± SE (n = 6) from two repeated experiments. ND, no detected. Different letters indicate significant differences between samples according to Tukey's multiple comparison tests at p < 0.05. Asterisks (* and **) indicate values that differ at p < 0.01 and p < 0.001 respecting control plants.

Figure 2

Expression of Adc, Samdc (isoforms 1–3), Zmspds1 and Zmspms genes in leaf blades of 11 d-old maize plants infected (5 dpi) or not with U. maydis. Total RNA was isolated from leaf blades of C and Chl samples as in Figure 1.