Abstract
Seed storage proteins, which are largely synthesized during maturation, are sorted to the protein storage vacuole (PSV) by the recognition of their vacuolar sorting determinants (VSD). We determine by transient expression assays in maturing soybean cotyledons that A1aB1b, one of soybean 11S globulin (glycinin) subunits, has C-terminal and physical-structure vacuolar sorting determinants (ctVSD and psVSD). In the study, we examined the PSV sorting of green fluorescent protein (GFP) fused to the VSD of A1aB1b (GFP-ctVSD or GFP-psVSD) by drug treatment and expression of dominant negative mutants of small GTPases experiments. The PSV sorting of GFP-ctVSD and GFP-psVSD was blocked by the treatment of brefeldin A or wortmanin. They colocalized with a ER or prevacuolar compartment marker in the presence of brefeldin A or wortmannin, respectively. Coexpression of sar1 or arf1 dominant negative mutants also inhibited their PSV sorting. We discussed the sorting mechanism of A1aB1b to the PSV.
