AUTHOR=Mori Akiko , Toyota Masatsugu , Shimada Masayoshi , Mekata Mika , Kurata Tetsuya , Tasaka Masao , Morita Miyo T. 

TITLE=Isolation of New Gravitropic Mutants under Hypergravity Conditions

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.01443

DOI=10.3389/fpls.2016.01443

ISSN=1664-462X

ABSTRACT=<p>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 in <italic>Arabidopsis</italic> stems 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 the <italic>endodermal-amyloplast less 1</italic> (<italic>eal1</italic>) mutant, which exhibits defective development of endodermal cells and gravitropism, we found that hypergravity (10 g) restored the reduced gravity responsiveness in <italic>eal1</italic> hypocotyls and could, therefore, be used to obtain mutants with further reduction in gravitropism in the <italic>eal1</italic> background. Using the new screening system, we successfully isolated six <italic>ene</italic> (<italic>enhancer of eal1</italic>) 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 in <italic>Arabidopsis</italic>.</p>