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Gene expression analysis in cadmium-stressed roots of a low cadmium-accumulating solanaceous plant, Solanum torvum.

Yamaguchi H, Fukuoka H, Arao T, Ohyama A, Nunome T, Miyatake K, Negoro S - J. Exp. Bot. (2009)

Bottom Line: In addition to induction of heavy metal chaperone proteins, antioxidative and sulphur-assimilating enzymes were induced, confirming that oxidative stress developed even using a mild Cd concentration.Rapid repression of dehydration-related transcription factors and aquaporin isoforms suggests that dehydration stress is a potential constituent of Cd-induced biochemical impediments.These transcriptional changes were also confirmed by real-time reverse transcription-PCR.

View Article: PubMed Central - PubMed

Affiliation: Molecular Genetics and Physiology Research Team, National Institute of Vegetable and Tea Science, 360 Kusawa, Ano-cho, Tsu, Mie, Japan. hyamagu@affrc.go.jp

ABSTRACT
Solanum torvum Sw. cv. Torubamubiga (TB) is a low cadmium (Cd)-accumulating plant. To elucidate the molecular mechanisms of the Cd acclimation process in TB roots, transcriptional regulation was analysed in response to mild Cd treatment: 0.1 muM CdCl(2) in hydroponic solution. A unigene set consisting of 6296 unigene sequences was constructed from 18 816 TB cDNAs. The distribution of functional categories was similar to tomato, while 330 unigenes were suggested to be TB specific. For expression profiling, the SuperSAGE method was adapted for use with Illumina sequencing technology. Expression tag libraries were constructed from Cd-treated (for 3 h, 1 d, and 3 d) and untreated roots, and 34 269 species of independent tags were collected. Moreover, 6237 tags were ascribed to the TB or eggplant (aubergine) unigene sequences. Time-course changes were examined, and 2049 up- and 2022 down-regulated tags were identified. Although no tags annotated to metal transporter genes were significantly regulated, a tag annotated to AtFRD3, a xylem-loading citrate transporter, was down-regulated. In addition to induction of heavy metal chaperone proteins, antioxidative and sulphur-assimilating enzymes were induced, confirming that oxidative stress developed even using a mild Cd concentration. Rapid repression of dehydration-related transcription factors and aquaporin isoforms suggests that dehydration stress is a potential constituent of Cd-induced biochemical impediments. These transcriptional changes were also confirmed by real-time reverse transcription-PCR. Further additions of TB unigene sequences and functional analysis of the regulated tags will reveal the molecular basis of the Cd acclimation process, including the low Cd-accumulating characteristics of TB.

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Cadmium and other metal contents in the roots and leaves of Cd-treated and untreated plants. (A) Cadmium, (B) iron, (C) manganese, and (D) zinc contents in the roots and leaves of Cd-treated and untreated TB plants. Cd0 indicates untreated plants and Cd3h, Cd1d, and Cd3d indicate plants treated with 0.1 μM for 3 h, 1 d, and 3 d, respectively. The same letters at the top of the bar indicate non-significant differences (P <0.05). Significance was evaluated by Tukey–Cramer's test. Bars indicate standard errors; n=8 (n=7 for leaves of plants treated for 3 d).
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fig3: Cadmium and other metal contents in the roots and leaves of Cd-treated and untreated plants. (A) Cadmium, (B) iron, (C) manganese, and (D) zinc contents in the roots and leaves of Cd-treated and untreated TB plants. Cd0 indicates untreated plants and Cd3h, Cd1d, and Cd3d indicate plants treated with 0.1 μM for 3 h, 1 d, and 3 d, respectively. The same letters at the top of the bar indicate non-significant differences (P <0.05). Significance was evaluated by Tukey–Cramer's test. Bars indicate standard errors; n=8 (n=7 for leaves of plants treated for 3 d).

Mentions: To investigate the time-course of transcriptional regulation in TB roots during physiologically mild Cd stress, 60-day-old TB plants were treated with 0.1 μM CdCl2 in hydroponic solution for either 3 h, 1 d, or 3 d. A very mild condition was employed to observe transcriptional changes in the Cd acclimation process, minimizing a vast range of the secondary effects caused by Cd stress. Plants treated for 3 d showed no apparent symptomatic changes in either roots or shoots. In Cd-treated TB plants, Cd accumulation in the roots was observed after just 3 h of treatment (Fig. 3A). Cd content in the roots continued to increase during Cd treatment, indicating the progression of Cd stress severity. In the leaves, however, it was not until after 1 d of treatment that Cd was detected in the tissue (less than the quantitative limit). Even after 3 d of treatment, Cd content in the leaves remained at quite a low level (0.12 mg kg−1 dry weight) compared with that in the roots. For other transition metal elements (Fig. 3B, C, D), slight increases in iron and/or manganese content in the roots were observed after 3 h (for manganese) and after 3 d (for iron and manganese), whereas zinc content in roots did not significantly change (P <0.05). The content of these metal elements in the leaves was not significantly changed. It was concluded that the early events of Cd-responsive transcriptional changes and subsequent responses during the acclimation process in root tissues could be captured with minimal disturbing side effects.


Gene expression analysis in cadmium-stressed roots of a low cadmium-accumulating solanaceous plant, Solanum torvum.

Yamaguchi H, Fukuoka H, Arao T, Ohyama A, Nunome T, Miyatake K, Negoro S - J. Exp. Bot. (2009)

Cadmium and other metal contents in the roots and leaves of Cd-treated and untreated plants. (A) Cadmium, (B) iron, (C) manganese, and (D) zinc contents in the roots and leaves of Cd-treated and untreated TB plants. Cd0 indicates untreated plants and Cd3h, Cd1d, and Cd3d indicate plants treated with 0.1 μM for 3 h, 1 d, and 3 d, respectively. The same letters at the top of the bar indicate non-significant differences (P <0.05). Significance was evaluated by Tukey–Cramer's test. Bars indicate standard errors; n=8 (n=7 for leaves of plants treated for 3 d).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2803209&req=5

fig3: Cadmium and other metal contents in the roots and leaves of Cd-treated and untreated plants. (A) Cadmium, (B) iron, (C) manganese, and (D) zinc contents in the roots and leaves of Cd-treated and untreated TB plants. Cd0 indicates untreated plants and Cd3h, Cd1d, and Cd3d indicate plants treated with 0.1 μM for 3 h, 1 d, and 3 d, respectively. The same letters at the top of the bar indicate non-significant differences (P <0.05). Significance was evaluated by Tukey–Cramer's test. Bars indicate standard errors; n=8 (n=7 for leaves of plants treated for 3 d).
Mentions: To investigate the time-course of transcriptional regulation in TB roots during physiologically mild Cd stress, 60-day-old TB plants were treated with 0.1 μM CdCl2 in hydroponic solution for either 3 h, 1 d, or 3 d. A very mild condition was employed to observe transcriptional changes in the Cd acclimation process, minimizing a vast range of the secondary effects caused by Cd stress. Plants treated for 3 d showed no apparent symptomatic changes in either roots or shoots. In Cd-treated TB plants, Cd accumulation in the roots was observed after just 3 h of treatment (Fig. 3A). Cd content in the roots continued to increase during Cd treatment, indicating the progression of Cd stress severity. In the leaves, however, it was not until after 1 d of treatment that Cd was detected in the tissue (less than the quantitative limit). Even after 3 d of treatment, Cd content in the leaves remained at quite a low level (0.12 mg kg−1 dry weight) compared with that in the roots. For other transition metal elements (Fig. 3B, C, D), slight increases in iron and/or manganese content in the roots were observed after 3 h (for manganese) and after 3 d (for iron and manganese), whereas zinc content in roots did not significantly change (P <0.05). The content of these metal elements in the leaves was not significantly changed. It was concluded that the early events of Cd-responsive transcriptional changes and subsequent responses during the acclimation process in root tissues could be captured with minimal disturbing side effects.

Bottom Line: In addition to induction of heavy metal chaperone proteins, antioxidative and sulphur-assimilating enzymes were induced, confirming that oxidative stress developed even using a mild Cd concentration.Rapid repression of dehydration-related transcription factors and aquaporin isoforms suggests that dehydration stress is a potential constituent of Cd-induced biochemical impediments.These transcriptional changes were also confirmed by real-time reverse transcription-PCR.

View Article: PubMed Central - PubMed

Affiliation: Molecular Genetics and Physiology Research Team, National Institute of Vegetable and Tea Science, 360 Kusawa, Ano-cho, Tsu, Mie, Japan. hyamagu@affrc.go.jp

ABSTRACT
Solanum torvum Sw. cv. Torubamubiga (TB) is a low cadmium (Cd)-accumulating plant. To elucidate the molecular mechanisms of the Cd acclimation process in TB roots, transcriptional regulation was analysed in response to mild Cd treatment: 0.1 muM CdCl(2) in hydroponic solution. A unigene set consisting of 6296 unigene sequences was constructed from 18 816 TB cDNAs. The distribution of functional categories was similar to tomato, while 330 unigenes were suggested to be TB specific. For expression profiling, the SuperSAGE method was adapted for use with Illumina sequencing technology. Expression tag libraries were constructed from Cd-treated (for 3 h, 1 d, and 3 d) and untreated roots, and 34 269 species of independent tags were collected. Moreover, 6237 tags were ascribed to the TB or eggplant (aubergine) unigene sequences. Time-course changes were examined, and 2049 up- and 2022 down-regulated tags were identified. Although no tags annotated to metal transporter genes were significantly regulated, a tag annotated to AtFRD3, a xylem-loading citrate transporter, was down-regulated. In addition to induction of heavy metal chaperone proteins, antioxidative and sulphur-assimilating enzymes were induced, confirming that oxidative stress developed even using a mild Cd concentration. Rapid repression of dehydration-related transcription factors and aquaporin isoforms suggests that dehydration stress is a potential constituent of Cd-induced biochemical impediments. These transcriptional changes were also confirmed by real-time reverse transcription-PCR. Further additions of TB unigene sequences and functional analysis of the regulated tags will reveal the molecular basis of the Cd acclimation process, including the low Cd-accumulating characteristics of TB.

Show MeSH
Related in: MedlinePlus