Molecular Mechanism Of Glycosylphosphatidylinositol-anchored Proteins-mediated Transport Of Receptor Kinases In Plants

Plants growth is sessile and has to defense fluctuating biotic and abiotic stress environment.The cytoplasmic membrane-localized receptor kinase proteins act as receptors to sense and transmit extracellular signals into intracellular to active cascade in cell.Althrough the signal sensing and transduction about receptor kinases are extensive investigated,little is known about their regulatory mechanisms.Glycosylphosphatidylinositol-anchored protein(GPI-AP)was confirmed to be involved in the trafficking of receptor kinases from endoplasmic reticulum(ER)to plasma memberane.In the previous research,it revealed that LORELEI like GPI-AP1(LLG1),a member of GPI-AP LORELEI(LRE)family,acts as chaperone for FERONIA(FER)receptor kinase and assists FER trafficking from ER to plasma membrane in Arabidopsis.Then the LLG1/FER complex senses and transmits external signals to downstream,resulting in a series of intracellular biochemical cascades.In this work,we investigated the molecular mechanism of plant GPI-AP for receptor kinase transport by combination assay in molecular biology,genetics,cell biology and biochemistry.We found that the FER homolog ANXUR1/ANXUR2 could not display polar localization to the plasma membrane at the tip of the pollen tube from RNAi materials of two other members of LLOREI family,LLG2 and LLG3.This indicates that LLG2/LLG3 assists in the transport of receptor kinase ANXUR1/ANXUR2.To further investigate the molecular mechanism of LRE family-mediated transport of Cr RLK1 L receptor-like kinases in plants,we found the LLG1 with the motif deletion of GPI modification could not assist the FER transport to the plasma membrane.It indicates that LLG1 relies on the GPI-modification to assist in the secretion of receptor-like kinases into the plasma membrane.In addition,the treatment of GPI ceramide remodeling inhibitor Myn and the mutation of p24 family protein EP24 affected FER receptor kinase transport and caused plant root hairs growth defective.All the results suggest that structural remodeling of GPI affects the specific transport of plant GPI-AP and FER receptor kinase.In summary,our study provided a theoretical basis for the analysis of the molecular mechanisms by which GPI-AP assists receptor-like kinase transport.