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Auxin regulates SNARE-dependent vacuolar morphology restricting cell size.

Löfke C, Dünser K, Scheuring D, Kleine-Vehn J - Elife (2015)

Bottom Line: Here, we reveal that the phytohormone auxin impacts on the shape of the biggest plant organelle, the vacuole.Genetic and pharmacological interference with the auxin effect on vacuolar SNAREs interrelates with auxin-resistant vacuolar morphogenesis and cell size regulation.Vacuolar SNARE VTI11 is strictly required for auxin-reliant vacuolar morphogenesis and loss of function renders cells largely insensitive to auxin-dependent growth inhibition.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Vienna, Austria.

ABSTRACT
The control of cellular growth is central to multicellular patterning. In plants, the encapsulating cell wall literally binds neighbouring cells to each other and limits cellular sliding/migration. In contrast to its developmental importance, growth regulation is poorly understood in plants. Here, we reveal that the phytohormone auxin impacts on the shape of the biggest plant organelle, the vacuole. TIR1/AFBs-dependent auxin signalling posttranslationally controls the protein abundance of vacuolar SNARE components. Genetic and pharmacological interference with the auxin effect on vacuolar SNAREs interrelates with auxin-resistant vacuolar morphogenesis and cell size regulation. Vacuolar SNARE VTI11 is strictly required for auxin-reliant vacuolar morphogenesis and loss of function renders cells largely insensitive to auxin-dependent growth inhibition. Our data suggests that the adaptation of SNARE-dependent vacuolar morphogenesis allows auxin to limit cellular expansion, contributing to root organ growth rates.

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Induction of a single SNARE component is not sufficient to affect vacuolar morphology.(A–D) Estradiol induction of VAMP711. pMDC7::citrus-flag (control) after DMSO (A) or estradiol (B) (2 µM) treatment. VAMP711 expression under control of an estradiol inducible promoter after DMSO (C) or estradiol (D) (2 µM) incubation. Vacuoles were decorated with FM4-64 (orange). (E) Semi-quantitative RT-PCR of VAMP711 in pMDC7::citrus-flag and pMDC7::VAMP711 expressing plants with (+) and without (−) estradiol induction (2 µM; 20 hr). UBQ-5 expression was used for normalisation. Depicted values represent quantification of mean grey values of corresponding bands. (F) Vacuolar morphology (vac. morph. [µm2]) index of estradiol induced pMDC7::citrus-flag and pMDC7::VAMP711 expressing seedlings compared to the uninduced control. Scale bar, 15 µm.DOI:http://dx.doi.org/10.7554/eLife.05868.012
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fig4s3: Induction of a single SNARE component is not sufficient to affect vacuolar morphology.(A–D) Estradiol induction of VAMP711. pMDC7::citrus-flag (control) after DMSO (A) or estradiol (B) (2 µM) treatment. VAMP711 expression under control of an estradiol inducible promoter after DMSO (C) or estradiol (D) (2 µM) incubation. Vacuoles were decorated with FM4-64 (orange). (E) Semi-quantitative RT-PCR of VAMP711 in pMDC7::citrus-flag and pMDC7::VAMP711 expressing plants with (+) and without (−) estradiol induction (2 µM; 20 hr). UBQ-5 expression was used for normalisation. Depicted values represent quantification of mean grey values of corresponding bands. (F) Vacuolar morphology (vac. morph. [µm2]) index of estradiol induced pMDC7::citrus-flag and pMDC7::VAMP711 expressing seedlings compared to the uninduced control. Scale bar, 15 µm.DOI:http://dx.doi.org/10.7554/eLife.05868.012

Mentions: Induction of a single SNARE component, such as VAMP711, did not affect vacuolar morphogenesis (Figure 4—figure supplement 3), possibly indicating the joint requirement of several complex components. Furthermore, auxin modulated SNARE proteins also when expressed under constitutive promoters (Figure 4A–D,I–N). This data implies that auxin affects the vacuolar SNAREs posttranslationally.


Auxin regulates SNARE-dependent vacuolar morphology restricting cell size.

Löfke C, Dünser K, Scheuring D, Kleine-Vehn J - Elife (2015)

Induction of a single SNARE component is not sufficient to affect vacuolar morphology.(A–D) Estradiol induction of VAMP711. pMDC7::citrus-flag (control) after DMSO (A) or estradiol (B) (2 µM) treatment. VAMP711 expression under control of an estradiol inducible promoter after DMSO (C) or estradiol (D) (2 µM) incubation. Vacuoles were decorated with FM4-64 (orange). (E) Semi-quantitative RT-PCR of VAMP711 in pMDC7::citrus-flag and pMDC7::VAMP711 expressing plants with (+) and without (−) estradiol induction (2 µM; 20 hr). UBQ-5 expression was used for normalisation. Depicted values represent quantification of mean grey values of corresponding bands. (F) Vacuolar morphology (vac. morph. [µm2]) index of estradiol induced pMDC7::citrus-flag and pMDC7::VAMP711 expressing seedlings compared to the uninduced control. Scale bar, 15 µm.DOI:http://dx.doi.org/10.7554/eLife.05868.012
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fig4s3: Induction of a single SNARE component is not sufficient to affect vacuolar morphology.(A–D) Estradiol induction of VAMP711. pMDC7::citrus-flag (control) after DMSO (A) or estradiol (B) (2 µM) treatment. VAMP711 expression under control of an estradiol inducible promoter after DMSO (C) or estradiol (D) (2 µM) incubation. Vacuoles were decorated with FM4-64 (orange). (E) Semi-quantitative RT-PCR of VAMP711 in pMDC7::citrus-flag and pMDC7::VAMP711 expressing plants with (+) and without (−) estradiol induction (2 µM; 20 hr). UBQ-5 expression was used for normalisation. Depicted values represent quantification of mean grey values of corresponding bands. (F) Vacuolar morphology (vac. morph. [µm2]) index of estradiol induced pMDC7::citrus-flag and pMDC7::VAMP711 expressing seedlings compared to the uninduced control. Scale bar, 15 µm.DOI:http://dx.doi.org/10.7554/eLife.05868.012
Mentions: Induction of a single SNARE component, such as VAMP711, did not affect vacuolar morphogenesis (Figure 4—figure supplement 3), possibly indicating the joint requirement of several complex components. Furthermore, auxin modulated SNARE proteins also when expressed under constitutive promoters (Figure 4A–D,I–N). This data implies that auxin affects the vacuolar SNAREs posttranslationally.

Bottom Line: Here, we reveal that the phytohormone auxin impacts on the shape of the biggest plant organelle, the vacuole.Genetic and pharmacological interference with the auxin effect on vacuolar SNAREs interrelates with auxin-resistant vacuolar morphogenesis and cell size regulation.Vacuolar SNARE VTI11 is strictly required for auxin-reliant vacuolar morphogenesis and loss of function renders cells largely insensitive to auxin-dependent growth inhibition.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Vienna, Austria.

ABSTRACT
The control of cellular growth is central to multicellular patterning. In plants, the encapsulating cell wall literally binds neighbouring cells to each other and limits cellular sliding/migration. In contrast to its developmental importance, growth regulation is poorly understood in plants. Here, we reveal that the phytohormone auxin impacts on the shape of the biggest plant organelle, the vacuole. TIR1/AFBs-dependent auxin signalling posttranslationally controls the protein abundance of vacuolar SNARE components. Genetic and pharmacological interference with the auxin effect on vacuolar SNAREs interrelates with auxin-resistant vacuolar morphogenesis and cell size regulation. Vacuolar SNARE VTI11 is strictly required for auxin-reliant vacuolar morphogenesis and loss of function renders cells largely insensitive to auxin-dependent growth inhibition. Our data suggests that the adaptation of SNARE-dependent vacuolar morphogenesis allows auxin to limit cellular expansion, contributing to root organ growth rates.

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