Analysis of genomic DNA of DcACS1, a 1-aminocyclopropane-1-carboxylate synthase gene, expressed in senescing petals of carnation (Dianthus caryophyllus) and its orthologous genes in D. superbus var. longicalycinus

Abstract

Carnation (Dianthus caryophyllus) flowers exhibit climacteric ethylene production followed by petal wilting, a senescence symptom. DcACS1, which encodes 1-aminocyclopropane-1-carboxylate synthase (ACS), is a gene involved in this phenomenon. We determined the genomic DNA structure of DcACS1 by genomic PCR. In the genome of 'Light Pink Barbara', we found two distinct nucleotide sequences: one corresponding to the gene previously shown as DcACS1, designated here as DcACS1a, and the other novel one designated as DcACS1b. It was revealed that both DcACS1a and DcACS1b have five exons and four introns. These two genes had almost identical nucleotide sequences in exons, but not in some introns and 3'-UTR. Analysis of transcript accumulation revealed that DcACS1b is expressed in senescing petals as well as DcACS1a. Genomic PCR analysis of 32 carnation cultivars showed that most cultivars have only DcACS1a and some have both DcACS1a and DcACS1b. Moreover, we found two DcACS1 orthologous genes with different nucleotide sequences from D. superbus var. longicalycinus, and designated them as DsuACS1a and DsuACS1b. Petals of D. superbus var. longicalycinus produced ethylene in response to exogenous ethylene, accompanying accumulation of DsuACS1 transcripts. These data suggest that climacteric ethylene production in flowers was genetically established before the cultivation of carnation.

Possible Origin of Two Variants of a Carnation 1-Aminocyclopropane-1-carboxylate Synthase Gene, DcACS1a and DcACS1b, as Suggested by Intron Structure in Homologous Genes in Dianthus Species

“…Carnation (Dianthus caryophyllus L.) 'Light Pink Barbara (LPB)' and D. superbus L. var. longicalycinus 'Metia Pink' (Sakata Seeds Corp., Yokohama, Japan) were the same as used previously (Harada et al, 2011). The other two accessions of D. superbus var.…”

“…DcACS1 was shown to be mainly responsible 444 for autocatalytic ethylene production in the petals (Jones, 2003;Jones and Woodson, 1999;Satoh, 2011;Shibuya and Ichimura, 2010;ten Have and Woltering, 1997); however, the genomic DNA structure of carnation ACS genes had not been reported until fairly recently when Harada et al (2011) investigated the structure of DcACS1 gene. Harada et al (2011) examined the genomic DNA structure of DcACS1 isolated from 'Light Pink Barbara' carnation, and showed that DcACS1 has two variants, distinguishing DcACS1a from DcACS1b. DcACS1a and DcACS1b genes consisted of five exons and four introns.…”

“…Furthermore, Harada et al (2011) identified orthologous ACS1 genes, DsuACS1a and DsuACS1b [hereafter, DsACS1a(MP) and DsACS1b(MP)], which are involved in autocatalytic ethylene production in petals of D. superbus var. longicalycinus 'Metia Pink'.…”

“…longicalycinus 'Metia Pink' (Harada et al, 2011), we considered the possible origin of two DcACS1 variants in carnation.…”

Flower senescence: some molecular aspects

“…exogenously applied ethylene has been found to induce autocatalytic ethylene production in petals of D. superbus var. longicalycinus with simultaneous accumulation of transcripts of DsuACS1 (Harada et al 2011a). ACC oxidase gene has been isolated from carnation (wang and woodson 1991).…”