title: The overexpression of OsNAC9 alters the root architecture of rice plants enhancing drought resistance and grain yield under field conditions.
abstract: Drought conditions limit agricultural production by preventing crops from reaching their genetically predetermined maximum yields. Here, we present the results of field evaluations of rice overexpressing OsNAC9, a member of the rice NAC domain family. Root-specific (RCc3) and constitutive (GOS2) promoters were used to overexpress OsNAC9 and produced the transgenic RCc3:OsNAC9 and GOS2:OsNAC9 plants. Field evaluations over two cultivating seasons showed that grain yields of the RCc3:OsNAC9 and the GOS2:OsNAC9 plants were increased by 13%-18% and 13%-32% under normal conditions, respectively. Under drought conditions, RCc3:OsNAC9 plants showed an increased grain yield of 28%-72%, whilst the GOS2:OsNAC9 plants remained unchanged. Both transgenic lines exhibited altered root architecture involving an enlarged stele and aerenchyma. The aerenchyma of RCc3:OsNAC9 roots was enlarged to a greater extent than those of GOS2:OsNAC9 and non-transgenic (NT) roots, suggesting the importance of this phenotype for enhanced drought resistance. Microarray experiments identified 40 up-regulated genes by more than threefold (P < 0.01) in the roots of both transgenic lines. These included 9-cis-epoxycarotenoid dioxygenase, an ABA biosynthesis gene, calcium-transporting ATPase, a component of the Ca(2+) signalling pathway involved in cortical cell death and aerenchyma formation, cinnamoyl CoA reductase 1, a gene involved in lignin biosynthesis, and wall-associated kinases¸ genes involved in cell elongation and morphogenesis. Interestingly, O-methyltransferase, a gene necessary for barrier formation, was specifically up-regulated only in the RCc3:OsNAC9 roots. Such up-regulated genes that are commonly and specifically up-regulated in OsNAC9 transgenic roots may account for the altered root architecture conferring increased drought resistance phenotype.
authors.affiliation: School of Biotechnology and Environmental Engineering, Myongji University, Yongin, Korea.
authors.forename: Mark C F R
authors.initials: MC
authors.lastname: Redillas
authors.forename: Jin S
authors.initials: JS
authors.lastname: Jeong
authors.forename: Youn S
authors.initials: YS
authors.lastname: Kim
authors.forename: Harin
authors.initials: H
authors.lastname: Jung
authors.forename: Seung W
authors.initials: SW
authors.lastname: Bang
authors.forename: Yang D
authors.initials: YD
authors.lastname: Choi
authors.forename: Sun-Hwa
authors.initials: SH
authors.lastname: Ha
authors.forename: Christophe
authors.initials: C
authors.lastname: Reuzeau
authors.forename: Ju-Kon
authors.initials: JK
authors.lastname: Kim
mesh_terms: D000222:Adaptation, Physiological; D000383:Agriculture; D055864:Droughts; D018506:Gene Expression Regulation, Plant; D012275:Oryza / Q000235:genetics / Q000254:growth & development* / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000033:anatomy & histology* / Q000254:growth & development; D030821:Plants, Genetically Modified; D060888:Real-Time Polymerase Chain Reaction; D012639:Seeds / Q000254:growth & development*; D013312:Stress, Physiological; D015854:Up-Regulation / Q000235:genetics
chemical_list: D010940:Plant Proteins