Abstract
The evolutionarily conserved small G-protein Ran plays important role in nuclear translocation of proteins, cell cycle regulation, and nuclear envelope maintenance in mammalian cells and yeast. Arabidopsis Ran proteins are encoded by a family of four genes and are highly conserved at the protein level. However, their biological functions are poorly understood. We report here that AtRAN1 plays an important role in vegetative growth and the molecular improvement of stress tolerance in Arabidopsis. AtRAN1 overexpression promoted vegetative growth and enhanced abiotic tolerance, while the atran1 atran3 double mutant showed higher freezing sensitivity than WT. The AtRAN1 gene is ubiquitously expressed in plants, and the expression levels are higher in the buds, flowers and siliques. Subcellular localization results showed that AtRAN1 is mainly localized in the nucleus, with some present in the cytoplasm. AtRAN1 could maintain cell division and cell cycle progression and promote the formation of an intact nuclear envelope, especially under freezing conditions.
Highlights
The small soluble GTP-binding protein Ran has been shown to be important for the nuclear translocation of proteins and cell cycle regulation in mammalian and yeast cells [1,2,3]
We found that the gene was ubiquitously expressed in plants, and the AtRAN1 expression levels were higher in the buds, flowers, leaves, and siliques, than in the other organs examined (Fig 1A)
The subcellular localization of AtRAN1::green fluorescent protein (GFP) was traced to the root cells of transgenic Arabidopsis steadily overexpressing the AtRAN1::GFP gene
Summary
The small soluble GTP-binding protein Ran has been shown to be important for the nuclear translocation of proteins and cell cycle regulation in mammalian and yeast cells [1,2,3]. Ran exerts its biological function by binding and hydrolyzing GTP. Intrinsic nucleotide exchange and GTP hydrolysis involving Ran are very low [4,5]. Many types of regulatory proteins have been identified that interact with Ran and stimulate its nucleotide exchange and GTP hydrolysis rates for thousands of times [6]. The identification of RanBP1 (Ran binding protein) and RanGAP (Ran GTPase-activating protein) made the function of Ran more clear in plants [5, 7]. RanGAP and its co-activator RanBP are excluded from the nucleus and deplete RanGTP from the cytoplasm
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