Thanks a lot, worked perfectly with no complications:
library(biomaRt)
host="plants.ensembl.org"
mysets<-listDatasets(useMart("plants_mart", host = host))
myusemart <- useDataset("zmays_eg_gene", mart = useMart("plants_mart", host = host))
resultTable <- getBM(attributes=c("go_id", "ensembl_gene_id"), mart = myusemart, filters = "ensembl_gene_id", values = c("Zm00001d002426"), uniqueRows=F)
# to get more info about available attributes and filters
listFilters(mart = myusemart, what = c("name", "description"))
listAttributes(myusemart)
Thanks