Phenotypic Characterization, Fine Mapping, and Altered Expression Profiling of Roses1 Mutation That Affects Organ Size and Water Loss Through Regulating Stomatal Density in Rice

Organ size is an important agronomic trait that directly affects the biomass of rice (Oryza sativa L.), thus identification and characterization of genes involved in organ size control would contribute to basic biology, as well as provide target genes for genetic manipulation of rice yield potential. Although organism or organ size is of pivotal importance, the molecular and genetic mechanisms underlying it remain far from understood. Here we report the isolation and characterization of reduced organ size with early senescence1 (roses1) mutant in rice. The roses1 mutant was obtained by ethyl methanesulfonate mutagenesis, and genetic analysis revealed that roses1 mutation is controlled by a single recessive nuclear gene. Distinct reduction in the size of organs in roses1 mutant plants was attributed to decreased cell number and cell size detected by histological analysis and the early leaf senescence with green and pale brown stripes, probably due to elevated stomata density detected by microscopy analysis. The ROSES1 gene was isolated by using map-based cloning strategy, encoding a BEL1-like homeobox transcription factor containing a plant-specific peroxidase (POX) domain of unknown function. The b-glucuronidase (GUS) activity driven by the ROSES1 promoter was strongly detected at the root meristem and elongation zone, shoot meristem, node, intercalary meristem of internode, leaf, inflorescence branch, and developing caryopsis and embryo. Differential gene expression analysis revealed potential regulatory networks involved in organ size control and stomata functioning that could be affected by the expression of the ROSES1 protein. X. Gong, Z. Zeng, and Y. Liu, College of Life Sciences, Chongqing Univ., Chongqing 400030, China; X. Gong and Z. Zhang, Yudongnan Academy of Agricultural Sciences, Chongqing 408000, China; J. Yue, W. Tang, X. Tang, X. Niu, D. Chen, and Y. Liu, College of Food Science and Engineering, Hefei Univ. of Technology, Hefei 230009, China; W. Tang and Y. Liu, Ministry of Education Key Laboratory for Bio-resource and Eco-environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan Univ., Chengdu 610064, China; X. Sang and G. He, Rice Research Institute, Southwest Univ., Chongqing 400716, China; F. Xiao, Dep. of Plant, Soil, and Entomological Sciences, Univ. of Idaho, Moscow, ID 83844. X. Gong, Z. Zhang, and J. Yue contributed equally to this work. Received 27 Oct. 2016. Accepted 22 Aug. 2017. *Corresponding author (liu_ys@scu.edu.cn, hegh@swu.edu.cn). Assigned to Associate Editor Lee Tarpley. Abbreviations: DEG, differentially expressed gene; DGE, differential gene expression; EMS, ethyl methanesulfonate; GFP, green fluorescent protein; GO, gene ontology; GUS, b-glucuronidase; LRI, Leaf-rolling index; OD649, optical density at 649 nm; OD665, optical density at 665 nm; PCR, polymerase chain reaction; POX, peroxidase; roses1, reduced organ size with early senescence1; SEM, scanning electron microscopy; SSR, simple sequence repeat; TEM, transmission electron microscopy; TF, transcription factor; WOX, WUSCHEL-related homeobox; WT, wild-type. Published in Crop Sci. 58:486–506 (2018). doi: 10.2135/cropsci2016.10. 0910 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA This is an open access article distributed under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Published January 12, 2018