Arabidopsis thalina Yellow Stripe1-Like4 and Yellow Stripe1-Like6 localize to internal cellular membranes and are involved in metal ion homeostasis

Several members of the Yellow Stripe1-Like (YSL) family of transporter proteins are able to transport metalniotian amine(NA) complexes. Substantial progress has been made in understanding the roles of the ArabidopsisYSLs that are most closely related to the founding member of the family, ZmYS1(e.g., AtYSL1, AtYSL2andAtYSL3), but there is little information concerning members of the other two well conserved YSL clades. Here, we provide evidence that At YSL4 and AtYSL6, which are the only genes in Arabidopsis belong toYSL Group II, are localized to vacuole membranes and to internal membranes rese mblingendo plasmic reticulum. Both single and double mutants for YSL4 and YSL6 were rigorously analyzed, and have surprisingly mild phenotypes, inspite of the strong and wider anging expression of YSL6. However, in the presence of toxic levels of Mn and Ni, plants with mutations in YSL4 and YSL6 and plants over expressingGFP-tagged YSL6 showed growth defects, indicating a role for these transporters in heavy metal stress responses.