title: Isolation of New Gravitropic Mutants under Hypergravity Conditions.
abstract: Forward genetics is a powerful approach used to link genotypes and phenotypes, and mutant screening/analysis has provided deep insights into many aspects of plant physiology. Gravitropism is a tropistic response in plants, in which hypocotyls and stems sense the direction of gravity and grow upward. Previous studies of gravitropic mutants have suggested that shoot endodermal cells inArabidopsisstems and hypocotyls are capable of sensing gravity (i.e., statocytes). In the present study, we report a new screening system using hypergravity conditions to isolate enhancers of gravitropism mutants, and we also describe a rapid and efficient genome mapping method, using next-generation sequencing (NGS) and single nucleotide polymorphism (SNP)-based markers. Using theendodermal-amyloplast less 1(eal1) mutant, which exhibits defective development of endodermal cells and gravitropism, we found that hypergravity (10 g) restored the reduced gravity responsiveness ineal1hypocotyls and could, therefore, be used to obtain mutants with further reduction in gravitropism in theeal1background. Using the new screening system, we successfully isolated sixene(enhancer of eal1) mutants that exhibited little or no gravitropism under hypergravity conditions, and using NGS and map-based cloning with SNP markers, we narrowed down the potential causative genes, which revealed a new genetic network for shoot gravitropism inArabidopsis.
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University Nagoya, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Mori
authors.affiliation: Department of Botany, University of WisconsinMadison, MadisonWI, USA; Japan Science and Technology Agency, Precursory Research for Embryonic Science and TechnologySaitama, Japan.
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Toyota
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology Ikoma, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Shimada
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology Ikoma, Japan.
authors.forename: Mika
authors.initials: M
authors.lastname: Mekata
authors.affiliation: Graduate School of Life Sciences, Tohoku University Sendai, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Kurata
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology Ikoma, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Tasaka
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya UniversityNagoya, Japan; CREST, Japan Science and Technology AgencyTokyo, Japan.
authors.forename: Miyo T
authors.initials: MT
authors.lastname: Morita
keywords: Arabidopsis thaliana; enhancer mutant; gravitropism; hypergravity; whole genome sequencing