Induction of the Arginine Decarboxylase ADC2 Gene Provides Evidence for the Involvement of Polyamines in the Wound Response in Arabidopsis

Abstract

Polyamines are small ubiquitous molecules that have been involved in nearly all developmental processes, including the stress response. Nevertheless, no direct evidence of a role of polyamines in the wound response has been described. We have studied the expression of genes involved in polyamine biosynthesis in response to mechanical injury. An increase in the expression of the arginine decarboxylase 2 (ADC2) gene in response to mechanical wounding and methyl jasmonate (JA) treatment in Arabidopsis was detected by using DNA microarray and RNA gel-blot analysis. No induction was observed for the ADC1 gene or other genes coding for spermidine and spermine synthases, suggesting that ADC2 is the only gene of polyamine biosynthesis involved in the wounding response mediated by JA. A transient increase in the level of free putrescine followed the increase in the mRNA level for ADC2. A decrease in the level of free spermine, coincident with the increase in putrescine after wounding, was also observed. Abscisic acid effected a strong induction on ADC2 expression and had no effect on ADC1 expression. Wound-induction of ADC2 mRNA was not prevented in the JA-insensitive coi1 mutant. The different pattern of expression of ADC2 gene in wild-type and coi1 mutant might be due to the dual regulation of ADC2 by abscisic acid and JA signaling pathways. This is the first direct evidence of a function of polyamines in the woundresponse, and it opens a new aspect of polyamines in plant biology.In contrast to animals, plants are unable to mobilize specialized cells devoted to wound healing after herbivore attach. Plant cells have evolved the capacity to activate defense responses that include wound healing and protection against further damage. Wound-activated repair/defense responses largely rely on the transcriptional activation of specific genes. These wound-inducible genes encode proteins implicated in activating wound signaling pathways, repairing damaged tissue, adjusting the metabolism for the production of toxins against the herbivore insect, and in the regulation of the internal nutritional demands (Leó n et al., 2001). In Arabidopsis, two different wound signaling pathways have been characterized (Titarenko et al., 1997). Upon wounding, expression of several genes is mediated by jasmonic acid (JA), whereas expression of others is independent of JA, but is activated by oligogalacturonides (Rojo et al., 1999). Very recently, a new mechanism, independent of JA or oligogalacturonides, has been reported to control the expression of the S-like RNase gene RNS1 (Taylor and Green, 1991) in systemically wounded tissue (LeBrasseur et al., 2002).The diamine putrescine and polyamines spermidine and spermine are small, ubiquitous compounds, positively charged at cytosolic pH, so they can interact with anionic macromolecules such as DNA, RNA, phospholipids, and proteins. Polyamines have been implicated in a variety of plant growth and developmental processes involving cell proliferation and differentiation, morphogenesis, dormancy and ge...

The Potassium-Dependent Transcriptome of Arabidopsis Reveals a Prominent Role of Jasmonic Acid in Nutrient Signaling

“…ADC2 induction has been reported for various stresses (Urano et al, 2003) and various growth regulators including JA (PerezAmador et al, 2002). By contrast, transcript levels of AtADC1 (spe1, At2g16500), which is not regulated by JA (Perez-Amador et al, 2002), remained unchanged in our treatments. Transcripts of the two arginase genes implicated in Orn production (usually a polyamine precursor) responded to K 1 treatments in Arabidopsis (compare Tables II and III).…”

BUD2, encoding an S-adenosylmethionine decarboxylase, is required for Arabidopsis growth and development

“…So far, two members of ADC, SPDS and SPMS genes [6,19,24,47], and four members of SAMDC genes have been identified in the Arabidopsis genome [29]. Previous studies indicated that ADC and SPDS members are functionally redundant, because a mutation in either gene member does not cause significant phenotypic changes [20,21,24,47].…”

“…At the cellular level, polyamines are organic cations, interacting with the macromolecules that possess anionic groups such as DNA, RNA, lipids and proteins, thereby influencing DNA conformation, gene expression and protein synthesis, and modulating enzyme activity. In higher plants, polyamines are able to affect membrane fluidity by binding to phospholipids in membrane [4] and mediate biotic and abiotic stress responses, such as pathogen infection, osmotic stress, potassium deficiency and wounding [5][6][7][8][9]. Previous observations revealed that polyamines may be involved in a variety of plant developmental processes, such as cell division, root initiation, somatic embryogenesis, xylogenesis, flower development, fruit ripening and senescence [3].…”

Polyamines: potent modulators of plant responses to stress

“…Therefore, it was concluded that ADC2 gene is responsible for the induction of ADC and PA biosynthesis under osmotic stress, since ADC1 gene expression was not affected in mutants. Perez-Amador et al (2002) have also shown that ADC2 gene expression is induced in response to mechanical wounding and methyl jasmonate treatment in A. thaliana. Other ADC1 mutant alleles (adc1-2, adc1-3) and ADC2 (adc2-3, adc2-4) are more sensitive to freezing but this phenotype is partially overcome by exogenous application of Put (Cuevas et al 2008).…”