RAN1 is involved in plant cold resistance and development in rice (Oryza sativa).

Peipei Xu,Weiming Cai

doi:10.1093/jxb/eru178

Abstract

Of the diverse abiotic stresses, low temperature is one of the major limiting factors that lead to a series of morphological, physiological, biochemical, and molecular changes in plants. Ran, an evolutionarily conserved small G-protein family, has been shown to be essential for the nuclear translocation of proteins. It also mediates the regulation of cell cycle progression in mammalian cells. However, little is known about Ran function in rice (Oryza sativa). We report here that Ran gene OsRAN1 is essential for the molecular improvement of rice for cold tolerance. Ran also affects plant morphogenesis in transgenic Arabidopsis thaliana. OsRAN1 is ubiquitously expressed in rice tissues with the highest expression in the spike. The levels of mRNA encoding OsRAN1 were greatly increased by cold and indoleacetic acid treatment rather than by addition of salt and polyethylene glycol. Further, OsRAN1 overexpression in Arabidopsis increased tiller number, and altered root development. OsRAN1 overexpression in rice improves cold tolerance. The levels of cellular free Pro and sugar levels were highly increased in transgenic plants under cold stress. Under cold stress, OsRAN1 maintained cell division and cell cycle progression, and also promoted the formation of an intact nuclear envelope. The results suggest that OsRAN1 protein plays an important role in the regulation of cellular mitosis and the auxin signalling pathway.

Highlights

Rasrelated nuclear protein (Ran) is a small GTPase that is essential for nuclear transport, nuclear assembly, mRNA processing, and cell cycle control, and is the only known member of the family of small GTP-binding proteins primarily localized inside the nucleus (Ciciarello et al, 2007; Di Fiore et al, 2004)
The data suggest that OsRAN1 predominantly responds to low temperature and indoleacetic acid (IAA) treatment compared with salt and drought stress
Exogenous applications of IAA addressed the phenotype of fewer lateral roots (Fig. 4). These results demonstrated that OsRAN1 controls development of shoots and the roots probably by affecting IAA signalling in the transgenic Arabidopsis

Summary

Introduction

Ran is a small GTPase that is essential for nuclear transport, nuclear assembly, mRNA processing, and cell cycle control, and is the only known member of the family of small GTP-binding proteins primarily localized inside the nucleus (Ciciarello et al, 2007; Di Fiore et al, 2004). As RanGAP and RanBP1 (Ran binding protein 1) are excluded from the nucleus, they cooperate in the cytoplasm to deplete RanGTP (Bischoff and Ponstingl, 1991; Bischoff and Ponstingl, 1995; Ramdas et al., 1991). Owing to the high similarity in amino acid sequence and subcellular localization, plant Ran proteins are probably highly conserved with their mammalian and yeast counterparts in nucleo-cytoplasmic trafficking and mitotic processes (Wang et al, 2006)

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