Responses of Polyamine-Metabolic Genes to Polyamines and Plant Stress Hormones in Arabidopsis Seedlings.

Yusaku Yariuchi,Yoshiteru Noutoshi,Takashi Okamoto,Taku Takahashi

doi:10.3390/cells10123283

Abstract

In plants, many of the enzymes in polyamine metabolism are encoded by multiple genes, whose expressions are differentially regulated under different physiological conditions. For comprehensive understanding of their regulation during the seedling growth stage, we examined the expression of polyamine metabolic genes in response to polyamines and stress-related plant hormones in Arabidopsis thaliana. While confirming previous findings such as induction of many of the genes by abscisic acid, induction of arginase genes and a copper amine oxidase gene, CuAOα3, by methyl jasmonate, that of an arginine decarboxylase gene, ADC2, and a spermine synthase gene, SPMS, by salicylic acid, and negative feedback regulation of thermospermine biosynthetic genes by thermospermine, our results showed that expressions of most of the genes are not responsive to exogenous polyamines. We thus examined expression of OsPAO6, which encodes an apoplastic polyamine oxidase and is strongly induced by polyamines in rice, by using the promoter-GUS fusion in transgenic Arabidopsis seedlings. The GUS activity was increased by treatment with methyl jasmonate but neither by polyamines nor by other plant hormones, suggesting a difference in the response to polyamines between Arabidopsis and rice. Our results provide a framework to study regulatory modules directing expression of each polyamine metabolic gene.

Highlights

IntroductionMany of the enzymes in polyamine biosynthetic and catabolic pathways are encoded by multiple genes, which show differential expression patterns under different physiological conditions and in different tissues
Polyamines function in various aspects of plant development and stress responses.In land plants, many of the enzymes in polyamine biosynthetic and catabolic pathways are encoded by multiple genes, which show differential expression patterns under different physiological conditions and in different tissues
We examined expressions of all 27 genes directly involved in polyamine biosynthesis and degradation in 7-day-old seedlings of Arabidopsis grown in liquid media

Summary

Introduction

Many of the enzymes in polyamine biosynthetic and catabolic pathways are encoded by multiple genes, which show differential expression patterns under different physiological conditions and in different tissues. In Arabidopsis thaliana, there are two genes encoding arginine decarboxylase (ADC), a key enzyme for putrescine biosynthesis, ADC1 and ADC2. The Arabidopsis genome has two genes encoding a dual functional arginase/agmatinase, ARGAH1 and ARGAH2. Expression of both genes is co-regulated with ADC2 in response to abscisic acid (ABA), methyl jasmonate (MeJA), drought, cold, and high salinity, suggesting that the agmatinase pathway may be a major contributor to putrescine biosynthesis under stress conditions [10]. ABA upregulates the expression of a gene for spermine synthase, SPMS [11]. Biosynthesis of spermidine, spermine, and thermospermine requires decarboxylated S-adenosyl methionine as an aminopropyl donor, which is supplied by

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