Delineating the roles of the Arabidopsis sku11 and wvd7 genes in root cell expansion.

摘要

The overall goal of this study was to elucidate molecular mechanisms controlling organ shape during plant growth and development, focusing on cell expansion processes in the Arabidopsis root. While wild type roots grow in a downward direction on tilted hard-agar surfaces and exhibit a sinusoidal waving pattern of growth, Arabidopsis cell expansion mutants often times have altered root-waving patterns and can grow askew. Here, we describe the phenotypic, genetic, and molecular characterization of two Arabidopsis cell expansion mutants we identified named sku11 and wvd7 (wave dampened 7).;sku11 roots skew to the right while waving down hard agar surfaces and exhibit abnormally slow bending kinetics upon gravistimulation. sku11 plants have additional cell expansion phenotypes including misshapen trichomes, flowers, leaves, and cotyledons. We found that sku11 roots responded abnormally to exogenously applied auxin-interfering drugs. We also determined that auxin transport and accumulation were altered in sku11 roots. Positional cloning of the EMS generated sku11-1 mutation uncovered a nonsense mutation in the ANGUSTIFOLIA (AN) gene. The AN gene is predicted to encode a protein with significant amino acid sequence identity to C-terminal Binding Protein/Brefeldin Adenosin Ribosylated Substrates (CtBP/BARS) proteins. In animals, CtBP/BARS function as regulators of vesicle budding from Golgi stacks. Consistent with a similar function for AN in plants, we identified defects in vesicle trafficking within the root cells of sku11 plants treated with the fungal toxin Brefeldin A. Taken together, our data suggest that SKU11 regulates the trafficking of proteins involved in auxin transport, which in turn affects cell expansion and organ growth.;The wvd7 mutant produces roots that are significantly shorter than wild type and do not wave on tilted agar surfaces. We determined that the wvd7 mutation resulted from a T-DNA insertion in the CAND1 gene. CAND1 encodes a negative regulator of the SCFtir system, which targets the ubiquitination and degradation of proteins involved in auxin signaling. It had been found that the CAND1 protein transiently sequesters one of the SCFtir core proteins, CULLIN1. Given that wvd7 roots lack the cyclic changes in cell expansion that produce the root-waving growth pattern, we hypothesized that the CAND1 protein is a master regulator of a circumnutation process regulating auxin response genes and organ growth. Our tests of that hypothesis are presented herein.