Abstract
To elucidate the molecular mechanism of the shoot gravitropism, we have isolated many shoot gravitropism (sgr) mutants in Arabidopsis. Previously we have described zig/sgr-4 mutant exhibited abnormal shoot gravitropism and morphological defects in stems and leaves. In zig-1, defective vacuoles were formed in the gravity-sensing endodermal cells, while the fragmented vacuoles or abnormal vesicles were observed in other tissues. ZIG encodes AtVTI11, a Qb-SNARE that is likely to function in the trans Golgi network-vacuole vesicle transport pathway. Thus, the vesicle transport mediated by ZIG may have pleiotropic functions in planta. To dissect ZIG function genetically, we performed a screening for the second mutation that can suppress defects of zig-1. The suppressor lines were isolated from zig-1 seeds mutagenized by EMS. The zig suppressor 3 (zip3) partially suppressed both abnormal gravitropism and morphology of zig-1. We have cloned the ZIP3 gene and its functional analysis is in progress.
