Interactions between polyamines and abiotic stress pathway responses unraveled by transcriptome analysis of polyamine overproducers

Abstract

Plant development and productivity are negatively regulated by adverse environmental conditions. The identification of stress-regulatory genes, networks, and signaling molecules should allow the development of novel strategies to obtain tolerant plants. Polyamines (PAs) are polycationic compounds with a recognized role in plant growth and development, as well as in abiotic and biotic stress responses. During the last years, knowledge on PA functions has been achieved using genetically modified plants with altered PA levels. In this review, we combine the information obtained from global transcriptome analyses in transgenic Arabidopsis plants with altered putrescine or spermine levels. Comparison of common and specific gene networks affected by elevation of endogenous PAs, support the view that these compounds actively participate in stress signaling through intricate crosstalks with abscisic acid (ABA), Ca(2+) signaling and other hormonal pathways in plant defense and development.

FIG. 1.

Polyamine biosynthesis pathway in Arabidopsis thaliana. Effects of ADC2, SAMDC1, or SPMS overexpression: overexpressed genes on studies cited in this review are highlighted in boxes; arrows indicate the effects on PA levels driven by overexpression of different PA biosynthesis genes. ACL5, ACAULIS5; ADC: arginine decarboxylase; AIH: agmatine iminohydrolase; CPA: N-carbamoylputrescine amidohydrolase; dcSAM: decarboxylated S-adenosylmethionine; SAM: S-adenosylmethionine; SAMDC: S-adenosylmethionine decarboxylase; SPDS: spermidine synthase; SPMS: spermine synthase. tSPMS: thermospermine synthase.

FIG. 2.

Expression profiles of common upregulated genes in PA overproducer plants. Left: Venn diagram analysis of common up- and downregulated genes from ADC2, SAMDC1, and SPMS overexpressor plants. Values represent the number of transcripts over and underexpressed in transgenic plants relative to wild-type Col-0 plants. Red box: E-northern heat map analysis of the 71 common upregulated genes in the three PA overproducer plants using abiotic stress series from BAR (Toufighi et al., 2005). Rows represent genes and columns represent experimental conditions. The color at a point represents the log2 of the ratio of the average of replicate treatments relative to the average of corresponding controls. The scale is shown in the figures.

FIG. 3.

Comparative analysis of expression profiles of common differentially expressed genes from ADC2, SAMDC1, and SPMS overexpressing plants. Only hormone-related genes are shown. Left: MAPMAN analysis (Thimm et al., ; Usadel et al., 2005). The signal from transgenic plants is expressed as a ratio relative to the signal in wild-type Col-0 plants converted to a log2 scale, and displayed. Right: Heatmap expression analysis using abiotic stress series from BAR (Toufighi et al., 2005). Rows represent genes and columns represent experimental conditions. The colour at a point represents the log2 of the ratio of the average of replicate treatments relative to the average of corresponding controls. The scale is shown in the figures. Orange boxes: ADC2 overexpressing plants. Blue boxes: SAMDC1 overexpressing plants; yellow boxes: SPMS overexpressing plants.

FIG. 4.

Comparative analysis of expression profiles of common differentially expressed genes from ADC2, SAMDC1, and SPMS overexpressing plants. Only signaling-related genes are shown. Left: MAPMAN analysis (Thimm et al., ; Usadel et al., 2005). The signal from transgenic plants is expressed as a ratio relative to the signal in wild-type Col-0 plants converted to a log2 scale, and displayed. Right: Heatmap expression analysis using abiotic stress series from BAR (Toufighi et al., 2005). Rows represent genes and columns represent experimental conditions. The colour at a point represents the log2 of the ratio of the average of replicate treatments relative to the average of corresponding controls. The scale is shown in the figures. Orange boxes: ADC2 overexpressing plants. Blue boxes: SAMDC1 overexpressing plants; yellow boxes: SPMS overexpressing plants.