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Stimulation of Cell Elongation by Tetraploidy in Hypocotyls of Dark-Grown Arabidopsis Seedlings.

Narukawa H, Yokoyama R, Komaki S, Sugimoto K, Nishitani K - PLoS ONE (2015)

Bottom Line: The longer hypocotyl in the tetraploid seedlings developed as a result of enhanced cell elongation rather than by an increase in cell number.DNA microarray analysis showed that genes involved in the transport of cuticle precursors were downregulated in a defined region of the tetraploid hypocotyl when compared to the diploid hypocotyl.Taken together, these data indicate that promotion of cell elongation is responsible for ploidy-dependent size determination in the Arabidopsis hypocotyl, and that this process is directly or indirectly related to cuticular function.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Plant Cell Wall Biology, Graduate School of Life Sciences, Tohoku University, Sendai, Japan.

ABSTRACT
Plant size is largely determined by the size of individual cells. A number of studies showed a link between ploidy and cell size in land plants, but this link remains controversial. In this study, post-germination growth, which occurs entirely by cell elongation, was examined in diploid and autotetraploid hypocotyls of Arabidopsis thaliana (L.) Heynh. Final hypocotyl length was longer in tetraploid plants than in diploid plants, particularly when seedlings were grown in the dark. The longer hypocotyl in the tetraploid seedlings developed as a result of enhanced cell elongation rather than by an increase in cell number. DNA microarray analysis showed that genes involved in the transport of cuticle precursors were downregulated in a defined region of the tetraploid hypocotyl when compared to the diploid hypocotyl. Cuticle permeability, as assessed by toluidine-blue staining, and cuticular structure, as visualized by electron microscopy, were altered in tetraploid plants. Taken together, these data indicate that promotion of cell elongation is responsible for ploidy-dependent size determination in the Arabidopsis hypocotyl, and that this process is directly or indirectly related to cuticular function.

No MeSH data available.


Global gene expression profiles in diploid and tetraploid dark-grown hypocotyls.(A) Scatter plot showing diploid and tetaraploid gene expression data in the apical growing region of 7-day-old dark-grown hypocotyls. Black dots represent genes whose expression levels differ by at least twofold between diploid and tetraploid. Gray dots represent genes below the twofold threshold. Genes with low signal-to-noise ratios were removed from analysis. (B) Significantly enriched Gene Ontology terms for genes whose expressions levels were at least twofold lower in tetraploid than in diploid plants. 2x, diploid plants; 4x, tetraploid plants.
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pone.0134547.g003: Global gene expression profiles in diploid and tetraploid dark-grown hypocotyls.(A) Scatter plot showing diploid and tetaraploid gene expression data in the apical growing region of 7-day-old dark-grown hypocotyls. Black dots represent genes whose expression levels differ by at least twofold between diploid and tetraploid. Gray dots represent genes below the twofold threshold. Genes with low signal-to-noise ratios were removed from analysis. (B) Significantly enriched Gene Ontology terms for genes whose expressions levels were at least twofold lower in tetraploid than in diploid plants. 2x, diploid plants; 4x, tetraploid plants.

Mentions: Microarray transcriptome profiles of diploid and tetraploid plants were compared to identify ploidy-related genes involved in the determination of cell size. We noted that the cell elongation zone in the etiolated hypocotyl of Arabidopsis was restricted to the apical region (S2 Fig), as observed previously by Gendreau et al. [11]. Microarray analysis was therefore performed using total RNA obtained from the apical 4 mm region of 7-day-old etiolated hypocotyls. The analysis identified 416 genes that were differentially expressed between diploid and tetraploid plants using a significance threshold of FDR < 0.1 and a twofold differential cutoff (Fig 3A; S2 and S3 Tables). Approximately three-quarters (305) of the differentially expressed transcripts were more abundant in the tetraploid plants, and one quarter (111) was more abundant in diploid plants. Genes associated with three Gene Ontology (GO) terms (lipid transport, lipid localization and lipid binding) were enriched in the subset of genes repressed in tetraploid plants (Fig 3B). Five of these genes encode lipid transfer proteins (LTPs) (S4 Table), which are putatively implicated in cuticle formation [20]. Downregulated expression of these LTP genes in tetraploid plants was confirmed by real time RT-PCR analysis (S3 Fig). No enriched GO terms were found for genes upregulated in tetraploid plants, and no GO terms associated with plant hormones or cell wall metabolism were found in the upregulated or repressed gene sets in tetraploid plants.


Stimulation of Cell Elongation by Tetraploidy in Hypocotyls of Dark-Grown Arabidopsis Seedlings.

Narukawa H, Yokoyama R, Komaki S, Sugimoto K, Nishitani K - PLoS ONE (2015)

Global gene expression profiles in diploid and tetraploid dark-grown hypocotyls.(A) Scatter plot showing diploid and tetaraploid gene expression data in the apical growing region of 7-day-old dark-grown hypocotyls. Black dots represent genes whose expression levels differ by at least twofold between diploid and tetraploid. Gray dots represent genes below the twofold threshold. Genes with low signal-to-noise ratios were removed from analysis. (B) Significantly enriched Gene Ontology terms for genes whose expressions levels were at least twofold lower in tetraploid than in diploid plants. 2x, diploid plants; 4x, tetraploid plants.
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pone.0134547.g003: Global gene expression profiles in diploid and tetraploid dark-grown hypocotyls.(A) Scatter plot showing diploid and tetaraploid gene expression data in the apical growing region of 7-day-old dark-grown hypocotyls. Black dots represent genes whose expression levels differ by at least twofold between diploid and tetraploid. Gray dots represent genes below the twofold threshold. Genes with low signal-to-noise ratios were removed from analysis. (B) Significantly enriched Gene Ontology terms for genes whose expressions levels were at least twofold lower in tetraploid than in diploid plants. 2x, diploid plants; 4x, tetraploid plants.
Mentions: Microarray transcriptome profiles of diploid and tetraploid plants were compared to identify ploidy-related genes involved in the determination of cell size. We noted that the cell elongation zone in the etiolated hypocotyl of Arabidopsis was restricted to the apical region (S2 Fig), as observed previously by Gendreau et al. [11]. Microarray analysis was therefore performed using total RNA obtained from the apical 4 mm region of 7-day-old etiolated hypocotyls. The analysis identified 416 genes that were differentially expressed between diploid and tetraploid plants using a significance threshold of FDR < 0.1 and a twofold differential cutoff (Fig 3A; S2 and S3 Tables). Approximately three-quarters (305) of the differentially expressed transcripts were more abundant in the tetraploid plants, and one quarter (111) was more abundant in diploid plants. Genes associated with three Gene Ontology (GO) terms (lipid transport, lipid localization and lipid binding) were enriched in the subset of genes repressed in tetraploid plants (Fig 3B). Five of these genes encode lipid transfer proteins (LTPs) (S4 Table), which are putatively implicated in cuticle formation [20]. Downregulated expression of these LTP genes in tetraploid plants was confirmed by real time RT-PCR analysis (S3 Fig). No enriched GO terms were found for genes upregulated in tetraploid plants, and no GO terms associated with plant hormones or cell wall metabolism were found in the upregulated or repressed gene sets in tetraploid plants.

Bottom Line: The longer hypocotyl in the tetraploid seedlings developed as a result of enhanced cell elongation rather than by an increase in cell number.DNA microarray analysis showed that genes involved in the transport of cuticle precursors were downregulated in a defined region of the tetraploid hypocotyl when compared to the diploid hypocotyl.Taken together, these data indicate that promotion of cell elongation is responsible for ploidy-dependent size determination in the Arabidopsis hypocotyl, and that this process is directly or indirectly related to cuticular function.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Plant Cell Wall Biology, Graduate School of Life Sciences, Tohoku University, Sendai, Japan.

ABSTRACT
Plant size is largely determined by the size of individual cells. A number of studies showed a link between ploidy and cell size in land plants, but this link remains controversial. In this study, post-germination growth, which occurs entirely by cell elongation, was examined in diploid and autotetraploid hypocotyls of Arabidopsis thaliana (L.) Heynh. Final hypocotyl length was longer in tetraploid plants than in diploid plants, particularly when seedlings were grown in the dark. The longer hypocotyl in the tetraploid seedlings developed as a result of enhanced cell elongation rather than by an increase in cell number. DNA microarray analysis showed that genes involved in the transport of cuticle precursors were downregulated in a defined region of the tetraploid hypocotyl when compared to the diploid hypocotyl. Cuticle permeability, as assessed by toluidine-blue staining, and cuticular structure, as visualized by electron microscopy, were altered in tetraploid plants. Taken together, these data indicate that promotion of cell elongation is responsible for ploidy-dependent size determination in the Arabidopsis hypocotyl, and that this process is directly or indirectly related to cuticular function.

No MeSH data available.