The phenomenon of root elongation and high respiration activity in the rolB-gene-enhanced FSL#35 variant of Lotus corniculatus FOX-SR line

Abstract

For systematic functional analysis of genes, we attempted the application of the FOX-hunting system to super growing-roots (SR) of legume species Lotus corniculatus which was previously reported by Himuro et al. (2011). In this study, we investigated the functional analysis of FSL#35, which was expressed by the rolB gene derived from the Agrobacterium rhizogenes Ri plasmid. In monoculture roots grown in liquid media, the FSL#35 showed specific phenotypes that increased root length, lateral root number and root surface area compared with SR. These enhanced phenotypes of FSL#35 were caused by cell profile alteration, while increased total root length and increased lateral root number were caused by the expansion of cortex cells and increased pericycle cells, respectively. In addition, the FSL#35 root showed high and specific respiration activity compared with SR. These results suggest that distinct cell profiles of FSL#35 were induced by the alteration of respiration activity in root tissue. The enhanced root growth in the FSL#35 root might be induced by alteration of ROS metabolisms. Investigating the details of the rolB gene function, for example by phytohormone analysis, will elucidate the novel benefits of the rolB gene for agriculture.