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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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Auxin affects cellular abundance of vacuolar SNAREs.(A–H) Maximum projection of tonoplast localised SNAREs and marker protein NET4A under high auxin conditions. pUBQ10::VAMP711-YFP expressing seedlings treated with DMSO (A) or NAA (B) (500 nM; 20 hr). 35S::SYP21-YFP expressing seedlings treated with DMSO (C) or NAA (D) (500 nM; 20 hr). SYP22::SYP22-GFP (in syp22) expressing seedlings treated with DMSO (E) or NAA (F) (500 nM; 20 hr). NET4A::NET4A-GFP expressing seedlings treated with DMSO (G) or NAA (H) (500 nM; 20 hr). 17–20 steps of 1 µm size were used for image acquisition. (I) Mean grey value of vacuolar SNAREs and tonoplast marker NET4A in DMSO control and auxin treatments (500 nM; 20 hr). Error bars represent s.e.m. For statistical analysis DMSO and NAA treatments were compared. Student's t-test p-values: **p < 0.01, ***p < 0.001. Scale bar: 15 µm.DOI:http://dx.doi.org/10.7554/eLife.05868.011
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fig4s2: Auxin affects cellular abundance of vacuolar SNAREs.(A–H) Maximum projection of tonoplast localised SNAREs and marker protein NET4A under high auxin conditions. pUBQ10::VAMP711-YFP expressing seedlings treated with DMSO (A) or NAA (B) (500 nM; 20 hr). 35S::SYP21-YFP expressing seedlings treated with DMSO (C) or NAA (D) (500 nM; 20 hr). SYP22::SYP22-GFP (in syp22) expressing seedlings treated with DMSO (E) or NAA (F) (500 nM; 20 hr). NET4A::NET4A-GFP expressing seedlings treated with DMSO (G) or NAA (H) (500 nM; 20 hr). 17–20 steps of 1 µm size were used for image acquisition. (I) Mean grey value of vacuolar SNAREs and tonoplast marker NET4A in DMSO control and auxin treatments (500 nM; 20 hr). Error bars represent s.e.m. For statistical analysis DMSO and NAA treatments were compared. Student's t-test p-values: **p < 0.01, ***p < 0.001. Scale bar: 15 µm.DOI:http://dx.doi.org/10.7554/eLife.05868.011

Mentions: To assess whether auxin treatments affect the overall cellular abundance of vacuolar SNAREs, we performed defined z-stack imaging. Subsequent maximum projections and intensity measurements confirmed that auxin increases cellular SNARE abundance at the tonoplast (Figure 4—figure supplement 2A–I). To further emphasize on this finding, we also performed western blots on excised root tips, similarly confirming our conclusion that auxin increases vacuolar SNARE abundance (Figure 4M,P).


Auxin regulates SNARE-dependent vacuolar morphology restricting cell size.

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

Auxin affects cellular abundance of vacuolar SNAREs.(A–H) Maximum projection of tonoplast localised SNAREs and marker protein NET4A under high auxin conditions. pUBQ10::VAMP711-YFP expressing seedlings treated with DMSO (A) or NAA (B) (500 nM; 20 hr). 35S::SYP21-YFP expressing seedlings treated with DMSO (C) or NAA (D) (500 nM; 20 hr). SYP22::SYP22-GFP (in syp22) expressing seedlings treated with DMSO (E) or NAA (F) (500 nM; 20 hr). NET4A::NET4A-GFP expressing seedlings treated with DMSO (G) or NAA (H) (500 nM; 20 hr). 17–20 steps of 1 µm size were used for image acquisition. (I) Mean grey value of vacuolar SNAREs and tonoplast marker NET4A in DMSO control and auxin treatments (500 nM; 20 hr). Error bars represent s.e.m. For statistical analysis DMSO and NAA treatments were compared. Student's t-test p-values: **p < 0.01, ***p < 0.001. Scale bar: 15 µm.DOI:http://dx.doi.org/10.7554/eLife.05868.011
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fig4s2: Auxin affects cellular abundance of vacuolar SNAREs.(A–H) Maximum projection of tonoplast localised SNAREs and marker protein NET4A under high auxin conditions. pUBQ10::VAMP711-YFP expressing seedlings treated with DMSO (A) or NAA (B) (500 nM; 20 hr). 35S::SYP21-YFP expressing seedlings treated with DMSO (C) or NAA (D) (500 nM; 20 hr). SYP22::SYP22-GFP (in syp22) expressing seedlings treated with DMSO (E) or NAA (F) (500 nM; 20 hr). NET4A::NET4A-GFP expressing seedlings treated with DMSO (G) or NAA (H) (500 nM; 20 hr). 17–20 steps of 1 µm size were used for image acquisition. (I) Mean grey value of vacuolar SNAREs and tonoplast marker NET4A in DMSO control and auxin treatments (500 nM; 20 hr). Error bars represent s.e.m. For statistical analysis DMSO and NAA treatments were compared. Student's t-test p-values: **p < 0.01, ***p < 0.001. Scale bar: 15 µm.DOI:http://dx.doi.org/10.7554/eLife.05868.011
Mentions: To assess whether auxin treatments affect the overall cellular abundance of vacuolar SNAREs, we performed defined z-stack imaging. Subsequent maximum projections and intensity measurements confirmed that auxin increases cellular SNARE abundance at the tonoplast (Figure 4—figure supplement 2A–I). To further emphasize on this finding, we also performed western blots on excised root tips, similarly confirming our conclusion that auxin increases vacuolar SNARE abundance (Figure 4M,P).

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.

Show MeSH
Related in: MedlinePlus