OsRAN2, essential for mitosis, enhances cold tolerance in rice by promoting export of intranuclear tubulin and maintaining cell division under cold stress

Abstract

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.

Potential involvement of drought-induced Ran GTPase CLRan1 in root growth enhancement in a xerophyte wild watermelon

“…Our data are consistent with a previous report that OsRan2-overexpressing transgenic rice acquired cold resistance by maintaining cell division under stress conditions. 18) We observed that transgenic Arabidopsis with higher CLRan1 transgene expression (lines T6 and T11) exhibited enhanced root growth in both unstressed and PEG-stressed conditions ( Fig. 5(C)).…”

“…[11][12][13] In plants, Ran GTPase is encoded by small gene family in Arabidopsis. [14][15][16] Overexpression of Ran GTPase genes from wheat (TaRan1) and rice (OsRan2) resulted in an increase in the mitotic index in root apical meristems and enhanced growth in transgenic rice and Arabidopsis, 17,18) indicating that the function of Ran GTPase is strongly associated with meristem activity and cellular proliferation in plants. External stimuli such as cold stress 18) and jasmonic acid 19) are known to induce Ran GTPase expression in plants, but to the best of our knowledge, a connection between drought response and Ran GTPase in plants has not been described thus far.…”

Cold tolerance in rice germinating seeds revealed by deep RNAseq analysis of contrasting indica genotypes

“…Recently, Endo et al [27] showed that OsCDKB2;1 (the same gene we identified) is involved in mitosis and DNA damage response in rice, which prevents delay mitotic cell-cycle progression in response to DNA damage checkpoints. Yet, Chen et al [28] over-expressed OsRAN2 gene, which is essential for mitosis and can promote intranuclear tubulin export at the end of mitosis. The transgenic rice plants maintained cell division under cold condition and enhanced cold tolerance (up to 80% survival, compared to 14% survival in WT plants).…”

Overexpressing components of the nuclear transport apparatus causes severe growth symptoms in tobacco leaves

“…16 Use of RNAi to knockdown expression of RAN1 in rice cause significant growth changes including reduced viability, changes in the response to ABA/salt stress and cell cycle defects. 17,18 Opposingly, when RAN from rice or wheat is overexpressed either in its native plant or in Arabidopsis it causes a range of phenotypic changes. Overexpression of OsRAN1, TaRAN1 or OsRAN2 in rice causes resistance to cold stress, 18,19 while overexpression of TaRAN1 or OsRAN1 in Arabidopsis alters apical dominance and plant stature.…”

“…17,18 Opposingly, when RAN from rice or wheat is overexpressed either in its native plant or in Arabidopsis it causes a range of phenotypic changes. Overexpression of OsRAN1, TaRAN1 or OsRAN2 in rice causes resistance to cold stress, 18,19 while overexpression of TaRAN1 or OsRAN1 in Arabidopsis alters apical dominance and plant stature. 19,20 Therefore given this breadth of information it is not surprising that when AtRAN1 is overexpressed in tobacco there is such a severe phenotype.…”