Abstract
To elucidate the molecular mechanism of the shoot gravitropism, we have isolated many shoot-gravitropism(sgr) mutants in Arabidopsis. The zigzag (zig/sgr4) mutant exhibited abnormal gravitropism in both infloresence stems and hypocotyls. Additionally, the stems elongated in a zigzag fashion. The ZIG gene encodes a SNARE, AtVTI11 that is homologous to yeast Vti1p involved in vesicle transport to vacuoles. To understand how vesicle traffic to vacuoles are involved in morphogenesis and gravitropism, we have isolated some suppressor mutants of zig-1. A dominant mutation zig suppressor 1(zip1) could almost completely suppress the defects of zig-1 mutant in both morphogenesis and gravitropism. Based on the map positon, we find a point mutation in AtVTI12 of zip1 zig-1. AtVTI12 is homologous to ZIG/AtVTI11, but both are functionally different. To understand how zip1 suppress the defect of zig-1 at a molecular level, biochemical and cytological analyses are now in progress.
