Plant growth depends on tightly coordinated auxin signaling and directional auxin transport,yet the molecular feedback mechanism that directly links these processes during root gravitropism has remained mechanisticall...Plant growth depends on tightly coordinated auxin signaling and directional auxin transport,yet the molecular feedback mechanism that directly links these processes during root gravitropism has remained mechanistically unresolved.The recent study by Rodriguez et al.(Cell,2025)reveals a novel cell-surface auxin signaling pathway.It is shown that gravity perception-induced initial auxin asymmetry activates transmembrane kinase 1(TMK1)in the lower side cells of the root.The activated TMK1 then interacts with pin-formed 2(PIN2)and phosphorylates its hydrophilic loop,thereby stabilizing the PIN2 protein.This asymmetric distribution of PIN2 further enhances the auxin flow on the lower side,thus forming a self-reinforcing positive feedback loop that drives force for root tip gravitropic bending.This study provides an updated perspective on the auxin signal and transport feedback,signifying a new advancement in our comprehension of the mechanisms underlying plant adaptive growth.展开更多
Clathrin-mediated endocytosis(CME)is the major endocytic pathway in eukaryotic cells that directly regulates abundance of plasma membrane proteins.Clathrin triskelia are composed of clathrin heavy chains(CHCs)and ligh...Clathrin-mediated endocytosis(CME)is the major endocytic pathway in eukaryotic cells that directly regulates abundance of plasma membrane proteins.Clathrin triskelia are composed of clathrin heavy chains(CHCs)and light chains(CLCs),and the phytohormone auxin differentially regulates membraneassociated CLCs and CHCs,modulating the endocytosis and therefore the distribution of auxin efflux transporter PIN-FORMED2(PIN2).However,the molecular mechanisms by which auxin regulates clathrin are still poorly understood.Transmembrane kinase(TMKs)family proteins are considered to contribute to auxin signaling and plant development;it remains unclear whether they are involved in PIN transport by CME.We assessed TMKs involvement in the regulation of clathrin by auxin,using genetic,pharmacological,and cytological approaches including live-cell imaging and immunofluorescence.In tmk1 mutant seedlings,auxin failed to rapidly regulate abundance of both CHC and CLC and to inhibit PIN2 endocytosis,leading to an impaired asymmetric distribution of PIN2 and therefore auxin.Furthermore,TMK3 and TMK4 were shown not to be involved in regulation of clathrin by auxin.In summary,TMK1 is essential for auxin-regulated clathrin recruitment and CME.TMK1therefore plays a critical role in the establishment of an asymmetric distribution of PIN2 and an auxin gradient during root gravitropism.展开更多
基金supported by the National Natural Science Foundation of China(32372599)the Agricultural Science and Technology Innovation Program(No.CAAS-BRC-GLCA-2025-01).
文摘Plant growth depends on tightly coordinated auxin signaling and directional auxin transport,yet the molecular feedback mechanism that directly links these processes during root gravitropism has remained mechanistically unresolved.The recent study by Rodriguez et al.(Cell,2025)reveals a novel cell-surface auxin signaling pathway.It is shown that gravity perception-induced initial auxin asymmetry activates transmembrane kinase 1(TMK1)in the lower side cells of the root.The activated TMK1 then interacts with pin-formed 2(PIN2)and phosphorylates its hydrophilic loop,thereby stabilizing the PIN2 protein.This asymmetric distribution of PIN2 further enhances the auxin flow on the lower side,thus forming a self-reinforcing positive feedback loop that drives force for root tip gravitropic bending.This study provides an updated perspective on the auxin signal and transport feedback,signifying a new advancement in our comprehension of the mechanisms underlying plant adaptive growth.
基金supported by grants to Jianwei Pan from the National Natural Science Foundation of China (91754104,31820103008,and 31670283)grants to Chao Wang from the Youth Program of National Natural Science Foundation of China (31801193)grants to Haijun Wu from the Startup Foundation for Introducing Talent of Lanzhou University (No.561120206)。
文摘Clathrin-mediated endocytosis(CME)is the major endocytic pathway in eukaryotic cells that directly regulates abundance of plasma membrane proteins.Clathrin triskelia are composed of clathrin heavy chains(CHCs)and light chains(CLCs),and the phytohormone auxin differentially regulates membraneassociated CLCs and CHCs,modulating the endocytosis and therefore the distribution of auxin efflux transporter PIN-FORMED2(PIN2).However,the molecular mechanisms by which auxin regulates clathrin are still poorly understood.Transmembrane kinase(TMKs)family proteins are considered to contribute to auxin signaling and plant development;it remains unclear whether they are involved in PIN transport by CME.We assessed TMKs involvement in the regulation of clathrin by auxin,using genetic,pharmacological,and cytological approaches including live-cell imaging and immunofluorescence.In tmk1 mutant seedlings,auxin failed to rapidly regulate abundance of both CHC and CLC and to inhibit PIN2 endocytosis,leading to an impaired asymmetric distribution of PIN2 and therefore auxin.Furthermore,TMK3 and TMK4 were shown not to be involved in regulation of clathrin by auxin.In summary,TMK1 is essential for auxin-regulated clathrin recruitment and CME.TMK1therefore plays a critical role in the establishment of an asymmetric distribution of PIN2 and an auxin gradient during root gravitropism.
