抄録
Auxinic herbicide, 2, 4-D is a chemical analogue of auxin, IAA. Traditionally it is believed that IAA and 2, 4-D share a common signaling pathway. However, the isolation of 2, 4-D resistant mutant aar1-1, identification of the gene SMAP1, which confers only 2, 4-D sensitivity, and 2,4-D specific degradation of root actin cytoskeleton and inhibition of cell division strongly suggest that 2, 4-D and IAA use both distinct and overlapping pathways to regulate Arabidopsis root growth. To provide a molecular explanation of 2, 4-D specific action, here we characterize the novel protein SMAP1. Our results revealed that SMAP1 acts as a positive regulator for 2, 4-D induced degradation of actin, cell division and cell elongation processes. The ubiquitin proteasome mutants,tir1-1 and axr1-12, which show enhanced resistance to 2, 4-D compared with IAA in root growth, were found to be resistant to 2, 4-D mediated actin degradation. Genetic interaction between SMAP1 and ubiquitin pathway was confirmed by analyzing the double mutant aar1 x tir1, which shows enhanced resistance to 2, 4-D for both root growth and actin degradation compared with their respective parental lines.
