Inositol 1,4,5-trisphosphate and Ran expression during simulated and real microgravity

Abstract

In order to gain further insight into the signal transduction pathway concerning gravitropism, we studied the expression profiles of mRNA in etiolated sunflower (Helianthus annuus L.) seedlings. Differential-display reverse transcriptase PCR product assayed by capillary electrophoresis revealed the small GTPase Ran, regulating nuclear import and export of proteins. Parallel analysis of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) release by a highly advanced system of metal-dye detection combined with high-performance liquid chromatography provided evidence that the second messenger Ins(1,4,5)P3 is modulated by changes of the gravity vector. Investigations by fast clinorotation and sounding rockets established a positive correlation between the Ins(1,4,5)P3 level and the expression rate of Ran mRNA during simulated and real microgravity. Since an asymmetric distribution of auxin during graviresponse is suggested to induce differential cell elongation, additional information on the perception and transduction pathways was achieved by auxin stimulation experiments. While we were able to demonstrate an auxin-dependent production of Ins(1,4,5)P3, the expression of Ran mRNA was not affected by auxin. Finally, besides the phosphoinositide system as one element of the signal transduction chain linking graviperception to graviresponse, a Ran-mediated interaction model of extracellular microgravity signal perception and intercellular transduction pathway is proposed.

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

“…2c,d). Ran GTPase in plants was shown to be involved in cell cycle regulation and response to phytohormones such as indoleacetic acid, jasmonic acid, and even to gravitropism (Kriegs et al . 2006; Miche et al .…”

“…2010). RAN probably acts as a mediator of signalling molecules in gravitropism (Kriegs, Theisen & Schnabl 2006). However, little is known about how Ran GTPase works in regulating the cellular biological response of plants to cold stress.…”

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

“…In fact, overexpression of OsRan2 was shown to rescue the impairment of intranuclear tubulin export and sustain cell division under cold stress in transgenic rice. 18) Furthermore, the levels of plant Ran GTPase were shown to respond to external physicochemical stimuli, such as auxin, jasmonic acid, and gravitropism, 17,19,29) raising a possibility that Ran GTPase may function as one of the factors integrating various intrinsic and extrinsic information for the regulation of cell cycle progression, which is a susceptible cellular processes under environmental stress condition. 18,30) In this study, we observed that roots of wild watermelon and vector-transformed Arabidopsis control plants showed contrasting responses to the PEG treatments.…”

Analysis of Differential Transcript Expression Reveals Time-Dependent Leaf Responses to Sclerotinia sclerotiorum in Wild and Cultivated Sunflower

“…In total, 20 anchored oligo-dT and arbitrary-primer combinations were performed with a PCR reaction as follows: 92°C for 5 min, ten cycles of 92°C for 30 s, 33°C for 1 min and 72°C for 1 min, 30 cycles of 95°C for 30 s, 64°C for 1 min and 72°C for 1 min, and a final extension at 72°C for 10 min. Modifications of oligo-dT-primer and random primer were used according to Kriegs et al (2006).…”

“…The modern technique of separating DNA molecules within gel-filled capillaries known as capillary gel electrophoresis (CE) is currently used for separation of nucleic acids. Although separation of nucleic acid fragments by CE is meanwhile routinely used, an application for separation of differential display fragments in plants is merely described so far (Kriegs et al 2006). One advantage of separation of cDNA fragments with CE is the possibility to analyse the peak data.…”