title: Root hair-specific EXPANSIN A7 is required for root hair elongation in Arabidopsis.
abstract: Expansins are non-hydrolytic cell wall-loosening proteins that are involved in the cell wall modifications that underlie many plant developmental processes. Root hair growth requires the accumulation of cell wall materials and dynamic cell wall modification at the tip region. Although several lines of indirect evidence support the idea that expansin-mediated wall modification occurs during root hair growth, the involvement of these proteins remains to be demonstrated in vivo. In this study, we used RNA interference (RNAi) to examine the biological function of Arabidopsis thaliana EXPANSIN A7 (AtEXPA7), which is expressed specifically in the root hair cell. The root hairspecific AtEXPA7 promoter was used to drive RNAi expression, which targeted two independent regions in the AtEXPA7 transcript. Quantitative reverse transcriptase-PCR analyses were used to examine AtEXPA7 transcript levels. In four independent RNAi transformant lines, RNAi expression reduced AtEXPA7 transcript levels by 25-58% compared to controls. Accordingly, the root hairs of RNAi transformant lines were 25-48% shorter than control plants and exhibited a broader range of lengths than the controls. Our results provide in vivo evidence that expansins are required for root hair tip growth.
authors.affiliation: Department of Biological Sciences and Genomics and Breeding Institute, Seoul National University, Seoul 151-742, Korea.
authors.forename: Changfa
authors.initials: C
authors.lastname: Lin
authors.forename: Hee-Seung
authors.initials: HS
authors.lastname: Choi
authors.forename: Hyung-Taeg
authors.initials: HT
authors.lastname: Cho
mesh_terms: D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D022081:Cell Surface Extensions / Q000502:physiology*; D003001:Cloning, Molecular; D008969:Molecular Sequence Data; D019441:Plant Epidermis / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D018517:Plant Roots / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D034622:RNA Interference; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; C560927:EXPANSIN A7 protein, Arabidopsis