Abstract
PIN-FORMED (PIN) proteins localize asymmetrically at the plasma membrane and mediate intercellular polar transport of the plant hormone auxin that is crucial for a multitude of developmental processes in plants. PIN localization is under extensive control by environmental or developmental cues, but mechanisms regulating PIN localization are not fully understood. Here we show that early endosomal components ARF GEF BEN1 and newly identified Sec1/Munc18 family protein BEN2 are involved in distinct steps of early endosomal trafficking. BEN1 and BEN2 are collectively required for polar PIN localization, for their dynamic repolarization, and consequently for auxin activity gradient formation and auxin-related developmental processes including embryonic patterning, organogenesis, and vasculature venation patterning. These results show that early endosomal trafficking is crucial for cell polarity and auxin-dependent regulation of plant architecture.
Highlights
Plant hormone auxin locally accumulates in plant tissues and regulates multiple processes of plant growth and development [1,2]
PIN proteins are rapidly shuttling between the plasma membrane and intracellular compartments, potentially allowing dynamic changes of the asymmetric localization according to developmental and environmental cues
By genetic and pharmacological inhibition of early endosomal trafficking, we revealed that another early endosomal protein, ARF GEF BEN1, is involved in early endosomal trafficking at a distinct step
Summary
Plant hormone auxin locally accumulates in plant tissues and regulates multiple processes of plant growth and development [1,2]. Directional intercellular transport of auxin underlies most of known auxin-dependent control of development, including embryogenesis, root and shoot organogenesis, vascular tissue formation and asymmetric phototropic and gravitropic growths [3]. This polar auxin transport is achieved by collective actions of auxin efflux and influx transporters [4,5,6]. Manipulation of polar PIN localization causes changes in auxin distribution and altered developmental and/or growth responses [7,9] Supported by these lines of evidence, it is widely accepted that polar localization of PIN proteins is essential in regulating auxin distribution in plant tissues
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