Mutational Analysis of Root Gravitropism and Phototropism of Arabidopsis thaliana Seedlings

Abstract

Root gravitropism and phototropism were analysed in young seedlings of Arabidopsis thaliana by a simple procedure using agar plates, by changing the position of plates or by covering the plates with black opaque sheet. Roots of A. thaliana seedlings growing on the surface of agar medium showed clear responses to gravity and light stimuli. A set of mutants with abnormal gravitropism or phototropism was isolated. Gravitropic mutants were separated into two types, reduced-response type and non-response type. The mutants were genetically divided into two complementation groups, aux1 and agr1. In both groups the reduced-response type mutants carried weaker genetic lesions, whereas the non-response type mutants carried heavier genetic lesions. Mutants with no phototropic response were classified into two complementation groups, rpt1 and rpt2. The root tropism mutants showed normal tropic responses in shoots, indicating that genetic regulation pathways are different in roots and shoots.