The author highlights his group’s research on the mechanistic characterizations of auxin exporters and importers in plants, with particular emphasis on the structure determination of these transporters using cryo-electron microscopy (cryo-EM). Auxin, the first plant hormone to be identified, is involved in nearly all aspects of plant growth, development, and responses to environmental cues. The biological activity of auxin depends on the establishment of local concentration gradients, which are generated through the process of polar auxin transport (PAT). Members of the PIN-FORMED (PIN) protein family and the AUXIN1/LIKE-AUXIN1 (AUX1/LAX) family are key components of PAT, mediating cellular auxin efflux and influx, respectively. Using cryo-EM single particle analysis, high-resolution structures of PIN1 and AUX1 were determined, revealing the overall architecture of each transporter as well as their modes of auxin and inhibitor binding. Biochemical analyses further demonstrated distinct transport mechanisms, showing that PIN1 functions as an auxin uniporter, whereas AUX1 acts as an auxin and proton symporter. Together, these findings advance our understanding of the molecular basis of PAT in plants, and provide a foundation for future agricultural applications targeting auxin transporters.
We acknowledge support from the National Natural Science Foundation of China (32322041, 32321001, and W2412029), the Scientific Research Innovation Capability Support Project for Young Faculty (ZYGXQNJSKYCXNLZCXM-B8 to L.S.), and Natural Science Foundation of Anhui Province (2408085JX005 to L.S.).
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