Transcriptomic Analysis Reveals That Reactive Oxygen Species and Genes Encoding Lipid Transfer Protein Are Associated with Tobacco Hairy Root Growth and Branch Development

Abstract

The hairy root, a specialized plant tissue that emerges from a cell transformed with transfer DNA (T-DNA) from Agrobacterium rhizogenes, can be used to study root biology and utilized in biotechnological applications. The rol genes are known to participate in the generation of hairy roots; however, the means by which the rol genes contribute to the initiation and the maintenance of hairy roots remains largely unknown. We demonstrated that tobacco hairy roots lacking either rolB or rolC exhibited fewer branch roots and lost their growth ability in long-term subculture. Additionally, a microarray analysis revealed that the expression of several genes encoding lipid transfer proteins (LTP) and reactive oxygen species (ROS)-related genes was significantly suppressed in rolB- or rolC-deficient hairy roots. We found that hairy root clones that exhibited greater branching expressed higher levels of RolB or RolC and the genes encoding LTP identified from the microarray. When hairy roots were compared with intact roots, the expression levels of LTP-encoding genes were dramatically different. In addition, ROS were present at lower levels in rolB- and rolC-deficient hairy roots. We therefore suggest that upregulating LTP and increasing the level of ROS is important for hairy root growth.