title: Enhanced tolerance to chilling stress in OsMYB3R-2 transgenic rice is mediated by alteration in cell cycle and ectopic expression of stress genes.
abstract: MYB transcription factors play central roles in plant responses to abiotic stresses. How stress affects development is poorly understood. Here, we show that OsMYB3R-2 functions in both stress and developmental processes in rice (Oryza sativa). Transgenic plants overexpressing OsMYB3R-2 exhibited enhanced cold tolerance. Cold treatment greatly induced the expression of OsMYB3R-2, which encodes an active transcription factor. We show that OsMYB3R-2 specifically bound to a mitosis-specific activator cis-element, (T/C)C(T/C)AACGG(T/C)(T/C)A, a conserved sequence that was found in promoters of cyclin genes such as OsCycB1;1 and OsKNOLLE2. In addition, overexpression of OsMYB3R-2 in rice led to higher transcript levels of several G2/M phase-specific genes, including OsCycB1;1, OsCycB2;1, OsCycB2;2, and OsCDC20.1, than those in OsMYB3R-2 antisense lines or wild-type plants in response to cold treatment. Flow cytometry analysis revealed an increased cell mitotic index in overexpressed transgenic lines of OsMYB3R-2 after cold treatment. Furthermore, resistance to cold stress in the transgenic plants overexpressing OsCycB1;1 was also enhanced. The level of cellular free proline was increased in the overexpressed rice lines of OsMYB3R-2 and OsCycB1;1 transgenic plants compared with wild-type plants under the cold treatment. These results suggest that OsMYB3R-2 targets OsCycB1;1 and regulates the progress of the cell cycle during chilling stress. OsCPT1, which may be involved in the dehydration-responsive element-binding factor 1A pathway, showed the same transcription pattern in response to cold as did OsCycB1;1 in transgenic rice. Therefore, a cold resistance mechanism in rice could be mediated by regulating the cell cycle, which is controlled by key genes including OsMYB3R-2.
authors.affiliation: Research Center for Molecular and Developmental Biology, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
authors.forename: Qibin
authors.initials: Q
authors.lastname: Ma
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Dai
authors.forename: Yunyuan
authors.initials: Y
authors.lastname: Xu
authors.forename: Jing
authors.initials: J
authors.lastname: Guo
authors.forename: Yaju
authors.initials: Y
authors.lastname: Liu
authors.forename: Na
authors.initials: N
authors.lastname: Chen
authors.forename: Jun
authors.initials: J
authors.lastname: Xiao
authors.forename: Dajian
authors.initials: D
authors.lastname: Zhang
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Xu
authors.forename: Xiansheng
authors.initials: X
authors.lastname: Zhang
authors.forename: Kang
authors.initials: K
authors.lastname: Chong
mesh_terms: D002453:Cell Cycle; D003080:Cold Temperature; D016213:Cyclins / Q000378:metabolism; D012275:Oryza / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D030821:Plants, Genetically Modified / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D013312:Stress, Physiological; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D014158:Transcription, Genetic
chemical_list: D016213:Cyclins; D010940:Plant Proteins; D012333:RNA, Messenger; D015534:Trans-Activators