Auxin regulates SNARE-dependent vacuolar morphology restricting cell size

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.DOI: http://dx.doi.org/10.7554/eLife.05868.001

Actin-dependent vacuolar occupancy of the cell determines auxin-induced growth repression

“…LatB treatment also reduced the size (width × length) of the largest luminal structure, which defines the vacuolar morphology index (Fig. S3D) (15). Similarly, Jasplakinolide (JASP)-dependent stabilization of actin affected the vacuolar shape and increased the vacuolar morphology index (Fig.…”

“…We recently reported that auxin controls the morphogenesis of the largest plant organelle, the vacuole in a TIR1/AFBs-dependent manner that is required for auxin-induced growth repression (15). Using confocal microscopy, we detected the actin cytoskeleton in the vicinity of the vacuole (Fig.…”

“…As previously reported, control of vacuolar morphology is required for auxin-dependent growth repression (15). We therefore tested whether the subcellular resistance to auxin would also lead to auxin-resistant cellular elongation in actin and myosin mutants.…”

“…Exogenous application of auxin leads to a significantly lower vacuolar morphology index in meristematic cells of the root epidermis ( Fig. 1 G, H, and J) (15). We also depleted cellular auxin by applying the auxin biosynthesis inhibitor kynurenine (Kyn), which leads to a significantly higher vacuolar morphology index in wildtype cells (15) (Fig.…”

“…1 G, H, and J) (15). We also depleted cellular auxin by applying the auxin biosynthesis inhibitor kynurenine (Kyn), which leads to a significantly higher vacuolar morphology index in wildtype cells (15) (Fig. 1 G, I, and J).…”