Explore The Cytological Function Of Arf-like GTPase ARLA1A In Arabidopsis And The Roles In Aba Response

ARL8B is a conserved Arf-like small G protein during evolution.In animal cells,the cytological function of ARL8 B has been studied relatively widely.ARL8 B can mediate the fusion of late endosomes and lysosomes and the transport of lysosomes to the periphery of the cell by regulating the HOPS subunit VPS41.However,whether the homologous protein ARLA1 A in Arabidopsis preserves the conserved functions remains unknown.In this study,we demonstrate that ARLA1 A can also interact and co-localize with VPS41 at some puncta in plants and a part of VPS41 transfers to the plasma membrane under overexpression of the constitutively activated ARLA1 A through biochemical,genetic and cell biology experiments.However,the co-localization analysis and pharmacological experiments show that ARLA1 A does not localize on the typical late endosomes/prevacuolar compartments and has cytological characteristics independent of VPS41,which is different from the subcelluar localization and function of ARL8 B in animal cell,implying that the ARL8 B homologous protein in plants may evolve plant-specific features.Physiological experiments show that the subcellular distribution of ARLA1 A is regulated by ABA.A part of ARLA1 A transfers to the plasma membrane and vacuole membrane under ABA treatment.The main root growth of plant overexpressing the constitutively activated ARLA1 A protein is more resistant to ABA treatment and the constitutively activated ARLA1 A significantly inhibits the response of the downstream effector genes in ABA signaling pathway.These results show ARLA1 A may participate in the ABA stress response.In summary,our work shows that the ARL8 B homologous protein ARLA1 A in plants not only has conserved functions,but also develops plant-specific roles during the evolutionary process.