Structure and Function of Auxin Transporters

Extracellular auxin maxima and minima are important to control plant developmental programs. Auxin gradients are provided by the concerted action of proteins from the three major plasma membrane auxin transporter classes AUX1/LAX, PIN and ABCB transporters. But neither genetic nor biochemical nor modelling approaches have been able to reliably assign the individual roles and interplay of these transporter types. Based on the thermodynamic properties of the transporters, we show here by mathematical modeling and computational simulations that the concerted action of different auxin transporter types allow the adjustment of specific transmembrane auxin gradients. The dynamic flexibility of the "auxin homeostats" comes at the cost of an energy-consuming "auxin cycling" across the membrane. An unexpected finding was that functional ABCB-PIN coupling appears to allow an optimization of the trade-off between the speed of auxin gradient adjustment on the one hand and ATP consumption and disturbance of general anion homeostasis on the other. In conclusion, our analyses provide fundamental insights into the thermodynamic constraints and flexibility of transmembrane auxin transport in plants.

show abstract

Comparative analysis of STP6 and STP10 rationalizes molecular selectivity in Sugar Transport Proteins

Andersen,

Bavnhøj,

Brag

et al. 2024

Preprint

Self Cite

View full text Add to dashboard Cite

Sugar distribution plays essential roles in plant energy, signaling, and defense mechanisms. Sugar Transport Proteins (STPs) are responsible for proton-driven cellular uptake of glucose, derived from sucrose in the apoplast. Few STPs also facilitate uptake of fructose, the other constituent of sucrose but the molecular features that define differences in specificity are unknown. Here we present a 3.2 Å crystal structure ofArabidopsis thalianaSTP6 in an inward occluded conformational state with glucose bound and show that it is both a glucose and fructose transporter. We perform a comparative analysis with the glucose-selective STP10 usingin-vivoandin-vitrobased systems and disclose how the kinetic transport properties are influenced by different experimental setup. Our work provides detailed insights into the fine-tuned dynamics of affinity-induced specificity for hexose uptake, ultimately showing how the position of a single methyl group in the binding site is sufficient to direct substrate specificity. These findings advance the understanding of hexose trafficking by STPs and extend the framework for engineering STP, and more broadly sugar transport, in the future.

show abstract

Structure and Function of Auxin Transporters

Cited by 4 publications

References 164 publications

Deciphering the auxin-ethylene crosstalk in petal abscission through auxin influx carrier IpAUX1 of Itoh peony ‘Bartzella’

Deciphering the auxin-ethylene crosstalk in petal abscission through auxin influx carrier IpAUX1 of Itoh peony ‘Bartzella’

An auxin homeostat allows plant cells to establish and control defined transmembrane auxin gradients

Comparative analysis of STP6 and STP10 rationalizes molecular selectivity in Sugar Transport Proteins

Contact Info

Product

Resources

About