Auxin regulates aquaporin function to facilitate lateral root emergence

Abstract

Aquaporins are membrane channels that facilitate water movement across cell membranes. In plants, aquaporins contribute to water relations. Here, we establish a new link between aquaporin-dependent tissue hydraulics and auxin-regulated root development in Arabidopsis thaliana. We report that most aquaporin genes are repressed during lateral root formation and by exogenous auxin treatment. Auxin reduces root hydraulic conductivity both at the cell and whole-organ levels. The highly expressed aquaporin PIP2;1 is progressively excluded from the site of the auxin response maximum in lateral root primordia (LRP) whilst being maintained at their base and underlying vascular tissues. Modelling predicts that the positive and negative perturbations of PIP2;1 expression alter water flow into LRP, thereby slowing lateral root emergence (LRE). Consistent with this mechanism, pip2;1 mutants and PIP2;1-overexpressing lines exhibit delayed LRE. We conclude that auxin promotes LRE by regulating the spatial and temporal distribution of aquaporin-dependent root tissue water transport.

Assessment of the requirement for aquaporins in the thylakoid membrane of plant chloroplasts to sustain photosynthetic water oxidation

“…When it comes to the regulation of MIPs activity, a number of factors have been proposed, including cGMP, divalent cations (e.g., Ca 2+ , Mn 2+ ), pH, phosphorylation, and voltage dependence [12]. Recent studies point to new modes of regulation for plasma membrane intrinsic protein's (PIPs), namely by auxin-mediated trafficking between plasma membrane and cytoplasm, indicating a dynamic control of their density in membranes [13,14]. Most recently, interaction of Arabidopsis PIPs with TIPs has been demonstrated when expressed in yeast and proposed to play a role in their targeting and activity regulation in plants [15].…”

Spatiotemporal Analysis of Localized Circadian Arrhythmias in Plant Roots

“…Voß et al (2015) reported that the phase reset might be necessary to ensure hydraulic isolation of cells in the branching root from other cells. Auxin, which is channeled via the lateral root primordium into overlying cells, represses the expression of genes encoding water channel proteins known as aquaporins, leading to complex spatiotemporal changes in hydraulic properties that are necessary for organ emergence (Péret et al, 2012). In addition, lateral root formation is known to be associated with differences in auxin and cytokinin concentrations (Laplaze et al, 2007), and cytokinin suppresses the expression of the clock gene TOC1 (Salomé et al, 2006).…”

Lateral root morphogenesis is dependent on the mechanical properties of the overlaying tissues

“…Biomechanical properties targeted by auxin include production of cell wall remodeling enzymes (21) through the IDA-HAE/HSL2 signalling pathway (24,25) and down-regulation of water channels termed aquaporins to alter hydraulic properties of overlaying tissues (23). Mutants lacking these auxin targets exhibit altered LRP shape (23).…”

“…Recent studies have highlighted the importance of the localized auxin signal originating from the tip of the LRP to induce specific physiological responses in overlaying tissues (22,23). Biomechanical properties targeted by auxin include production of cell wall remodeling enzymes (21) through the IDA-HAE/HSL2 signalling pathway (24,25) and down-regulation of water channels termed aquaporins to alter hydraulic properties of overlaying tissues (23).…”