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Stress regulated members of the plant organic cation transporter family are localized to the vacuolar membrane.

Küfner I, Koch W - BMC Res Notes (2008)

Bottom Line: Expression analysis with RNA Gel Blots showed a distinct, organ-specific expression pattern of the individual genes.In experiments with salt, drought and cold stress, we could show that AtOCT4, 5 and 6 are up-regulated during drought stress, AtOCT3 and 5 during cold stress and AtOCT 5 and 6 during salt stress treatments.Localisation of the proteins at the tonoplast and regulation of the gene expression under stress conditions suggests a specific role for the transporters in plant adaptation to environmental stress.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Plant Molecular Biology-Plant Physiology, Auf der Morgenstelle 1, 72076 Tübingen, Germany. isabell.kuefner@zmbp.uni-tuebingen.de

ABSTRACT

Background: In Arabidopsis six genes group into the gene family of the organic cation transporters (OCTs). In animals the members of the OCT-family are mostly characterized as polyspecific transporters involved in the homeostasis of solutes, the transport of monoamine neurotransmitters and the transport of choline and carnitine. In plants little is known about function, localisation and regulation of this gene family. Only one protein has been characterized as a carnitine transporter at the plasma membrane so far.

Findings: We localized the five uncharacterized members of the Arabidopsis OCT family, designated OCT2-OCT6, via GFP fusions and protoplast transformation to the tonoplast. Expression analysis with RNA Gel Blots showed a distinct, organ-specific expression pattern of the individual genes. With reporter gene fusion of four members we analyzed the tissue specific distribution of OCT2, 3, 4, and 6. In experiments with salt, drought and cold stress, we could show that AtOCT4, 5 and 6 are up-regulated during drought stress, AtOCT3 and 5 during cold stress and AtOCT 5 and 6 during salt stress treatments.

Conclusion: Localisation of the proteins at the tonoplast and regulation of the gene expression under stress conditions suggests a specific role for the transporters in plant adaptation to environmental stress.

No MeSH data available.


Related in: MedlinePlus

Specific expression of vacuolar AtOCTs during drought, cold and salt stress. A) Expression of AtOCTs in response to drought stress. Expression was monitored in seedlings at indicated time points by RNA-Gel-blot analysis. 20 minutes after initiation of desiccation transcripts of AtOCT4 5and 6 start to accumulate over a period of 8 hours, with a maximum around 2–4 hours. AtOCT5 and AtOCt6 respond with a strong accumulation of transcripts whereas AtOCT2 and AtOCT3 do not respond at all. B) Expression of AtOCTs in response to cold stress. Expression was monitored in seedlings at indicated time points by RNA-Gel-blot analysis after transfer of seedling to 4°C. Increased levels of transcript were found 20 minutes after induction for AtOCT3 and AtOCT5 with a transient increase over 2 hours and decreasing after 4 hours. AtOCT2, 4 and 6 do not respond to cold stress. C) Expression of AtOCTs in respond to salt stress. Transcripts of AtOCT4, 5 and 6 respond to salt stress, AtOCT5 and AtOC6 expression shows a maximum level of transcripts after 6 hours and AtOCT4 after 24 hours. The expression of AtOCT2 and 3 does not respond to salt stress.
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Figure 5: Specific expression of vacuolar AtOCTs during drought, cold and salt stress. A) Expression of AtOCTs in response to drought stress. Expression was monitored in seedlings at indicated time points by RNA-Gel-blot analysis. 20 minutes after initiation of desiccation transcripts of AtOCT4 5and 6 start to accumulate over a period of 8 hours, with a maximum around 2–4 hours. AtOCT5 and AtOCt6 respond with a strong accumulation of transcripts whereas AtOCT2 and AtOCT3 do not respond at all. B) Expression of AtOCTs in response to cold stress. Expression was monitored in seedlings at indicated time points by RNA-Gel-blot analysis after transfer of seedling to 4°C. Increased levels of transcript were found 20 minutes after induction for AtOCT3 and AtOCT5 with a transient increase over 2 hours and decreasing after 4 hours. AtOCT2, 4 and 6 do not respond to cold stress. C) Expression of AtOCTs in respond to salt stress. Transcripts of AtOCT4, 5 and 6 respond to salt stress, AtOCT5 and AtOC6 expression shows a maximum level of transcripts after 6 hours and AtOCT4 after 24 hours. The expression of AtOCT2 and 3 does not respond to salt stress.

Mentions: Since the vacuole is involved in many processes related to osmoregulation and homeostasis of solutes, we tested whether the expression of the AtOCTs responds to stress situations that are known to affect the homeostasis of the cytosol. Cold, drought and salt stress induce processes that involve the vacuole as an important buffering "tank". In the stress experiments we could show that the vacuolar AtOCTs respond differentially with enhanced expression in timing and strength to the treatments. Drought stress causes a rapid increase of AtOCT4, 5 and 6 transcripts within 20 minutes of the initiation of desiccation (Figure 5A). A maximum expression level was reached ~2 h after the start of treatment. AtOCT2 and 3 gene expression was not induced after drought. Cold treatment of the seedlings resulted in an increased expression level of AtOCT3 and 5 again within 20 minutes (Figure 5B). AtOCT2, 4 and 6 do not respond to cold stress treatment. In the salt stress experiment timing of the induction is slower but here AtOCT5 and AtOCT6 respond with increased expression levels six hours after exposure to salinity (Figure 5C). AtOCT2 and 3 do not respond and AtOCT4 expression is increased after 3 h and decreases with a second peak after 24 h. In all three experiments AtOCT5 expression responds with the strongest increase of transcript levels. AtOCT3 expression is only increased during cold stress treatment. The expression of AtOCT1, the plasmamembrane localized member of this family, is not induced after the stress treatments, but rather reduced upon drought and salt stress.


Stress regulated members of the plant organic cation transporter family are localized to the vacuolar membrane.

Küfner I, Koch W - BMC Res Notes (2008)

Specific expression of vacuolar AtOCTs during drought, cold and salt stress. A) Expression of AtOCTs in response to drought stress. Expression was monitored in seedlings at indicated time points by RNA-Gel-blot analysis. 20 minutes after initiation of desiccation transcripts of AtOCT4 5and 6 start to accumulate over a period of 8 hours, with a maximum around 2–4 hours. AtOCT5 and AtOCt6 respond with a strong accumulation of transcripts whereas AtOCT2 and AtOCT3 do not respond at all. B) Expression of AtOCTs in response to cold stress. Expression was monitored in seedlings at indicated time points by RNA-Gel-blot analysis after transfer of seedling to 4°C. Increased levels of transcript were found 20 minutes after induction for AtOCT3 and AtOCT5 with a transient increase over 2 hours and decreasing after 4 hours. AtOCT2, 4 and 6 do not respond to cold stress. C) Expression of AtOCTs in respond to salt stress. Transcripts of AtOCT4, 5 and 6 respond to salt stress, AtOCT5 and AtOC6 expression shows a maximum level of transcripts after 6 hours and AtOCT4 after 24 hours. The expression of AtOCT2 and 3 does not respond to salt stress.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 5: Specific expression of vacuolar AtOCTs during drought, cold and salt stress. A) Expression of AtOCTs in response to drought stress. Expression was monitored in seedlings at indicated time points by RNA-Gel-blot analysis. 20 minutes after initiation of desiccation transcripts of AtOCT4 5and 6 start to accumulate over a period of 8 hours, with a maximum around 2–4 hours. AtOCT5 and AtOCt6 respond with a strong accumulation of transcripts whereas AtOCT2 and AtOCT3 do not respond at all. B) Expression of AtOCTs in response to cold stress. Expression was monitored in seedlings at indicated time points by RNA-Gel-blot analysis after transfer of seedling to 4°C. Increased levels of transcript were found 20 minutes after induction for AtOCT3 and AtOCT5 with a transient increase over 2 hours and decreasing after 4 hours. AtOCT2, 4 and 6 do not respond to cold stress. C) Expression of AtOCTs in respond to salt stress. Transcripts of AtOCT4, 5 and 6 respond to salt stress, AtOCT5 and AtOC6 expression shows a maximum level of transcripts after 6 hours and AtOCT4 after 24 hours. The expression of AtOCT2 and 3 does not respond to salt stress.
Mentions: Since the vacuole is involved in many processes related to osmoregulation and homeostasis of solutes, we tested whether the expression of the AtOCTs responds to stress situations that are known to affect the homeostasis of the cytosol. Cold, drought and salt stress induce processes that involve the vacuole as an important buffering "tank". In the stress experiments we could show that the vacuolar AtOCTs respond differentially with enhanced expression in timing and strength to the treatments. Drought stress causes a rapid increase of AtOCT4, 5 and 6 transcripts within 20 minutes of the initiation of desiccation (Figure 5A). A maximum expression level was reached ~2 h after the start of treatment. AtOCT2 and 3 gene expression was not induced after drought. Cold treatment of the seedlings resulted in an increased expression level of AtOCT3 and 5 again within 20 minutes (Figure 5B). AtOCT2, 4 and 6 do not respond to cold stress treatment. In the salt stress experiment timing of the induction is slower but here AtOCT5 and AtOCT6 respond with increased expression levels six hours after exposure to salinity (Figure 5C). AtOCT2 and 3 do not respond and AtOCT4 expression is increased after 3 h and decreases with a second peak after 24 h. In all three experiments AtOCT5 expression responds with the strongest increase of transcript levels. AtOCT3 expression is only increased during cold stress treatment. The expression of AtOCT1, the plasmamembrane localized member of this family, is not induced after the stress treatments, but rather reduced upon drought and salt stress.

Bottom Line: Expression analysis with RNA Gel Blots showed a distinct, organ-specific expression pattern of the individual genes.In experiments with salt, drought and cold stress, we could show that AtOCT4, 5 and 6 are up-regulated during drought stress, AtOCT3 and 5 during cold stress and AtOCT 5 and 6 during salt stress treatments.Localisation of the proteins at the tonoplast and regulation of the gene expression under stress conditions suggests a specific role for the transporters in plant adaptation to environmental stress.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Plant Molecular Biology-Plant Physiology, Auf der Morgenstelle 1, 72076 Tübingen, Germany. isabell.kuefner@zmbp.uni-tuebingen.de

ABSTRACT

Background: In Arabidopsis six genes group into the gene family of the organic cation transporters (OCTs). In animals the members of the OCT-family are mostly characterized as polyspecific transporters involved in the homeostasis of solutes, the transport of monoamine neurotransmitters and the transport of choline and carnitine. In plants little is known about function, localisation and regulation of this gene family. Only one protein has been characterized as a carnitine transporter at the plasma membrane so far.

Findings: We localized the five uncharacterized members of the Arabidopsis OCT family, designated OCT2-OCT6, via GFP fusions and protoplast transformation to the tonoplast. Expression analysis with RNA Gel Blots showed a distinct, organ-specific expression pattern of the individual genes. With reporter gene fusion of four members we analyzed the tissue specific distribution of OCT2, 3, 4, and 6. In experiments with salt, drought and cold stress, we could show that AtOCT4, 5 and 6 are up-regulated during drought stress, AtOCT3 and 5 during cold stress and AtOCT 5 and 6 during salt stress treatments.

Conclusion: Localisation of the proteins at the tonoplast and regulation of the gene expression under stress conditions suggests a specific role for the transporters in plant adaptation to environmental stress.

No MeSH data available.


Related in: MedlinePlus