No abstract

Ran is an evolutionarily conserved eukaryotic GTPase. We previously identified a cDNA of TaRAN1, a novel Ran GTPase homologous gene in wheat (Triticum aestivum) and demonstrated that TaRAN1 is associated with regulation of genome integrity and cell division in yeast (Saccharomyces cerevisiae) systems. However, much less is known about the function of RAN in plant development. To analyze the possible biological roles of Ran GTPase, we overexpressed TaRAN1 in transgenic Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa). TaRAN1 overexpression increased the proportion of cells in the G2 phase of the cell cycle, which resulted in an elevated mitotic index and prolonged life cycle. Furthermore, it led to increased primordial tissue, reduced number of lateral roots, and stimulated hypersensitivity to exogenous auxin. The results suggest that Ran protein was involved in the regulation of mitotic progress, either in the shoot apical meristem or the root meristem zone in plants, where auxin signaling is involved. This article determines the function of RAN in plant development mediated by the cell cycle and its novel role in meristem initiation mediated by auxin signaling.

With global climate change, abnormally low temperatures have affected the world's rice production. Many genes have been shown to be essential for molecular improvement of rice cold-tolerance traits. However, less is known about the molecular cellular mechanism of their response to cold stress. Here, we investigated OsRAN2 involved in regulation of cell division during cold stress in rice. Expression of OsRAN2 was increased under cold treatment, but not during salt and drought stress. The mean root mitotic index was closely related to the expression level of OsRAN2. Knockdown transgenic rice lines showed an aberrant organization of spindles during mitosis and stunted growth during development. Overexpression of OsRAN2 enhanced cold tolerance in rice. The transgenic rice overexpressing OsRAN2 showed maintained cell division, decreased proportion of cells with intranuclear tubulin and formation of a normal nuclear envelope under the cold condition. Our study suggests a mechanism for OsRAN2 in regulating cold resistance in rice by maintaining cell division through promoting the normal export of intranuclear tubulin at the end of mitosis. This insight could help improve the cold-tolerance trait in rice.