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Oxidative stress and NO signalling in the root apex as an early response to changes in gravity conditions.

Mugnai S, Pandolfi C, Masi E, Azzarello E, Monetti E, Comparini D, Voigt B, Volkmann D, Mancuso S - Biomed Res Int (2014)

Bottom Line: The same results were obtained by ROS measurement.The detrimental effect of D'orenone, disrupting the polarised auxin transport, on the onset of the oxygen peaks during the microgravity period was also evaluated.Results indicates an active role of NO and ROS as messengers during the gravitropic response, with probable implications in the auxin redistribution.

View Article: PubMed Central - PubMed

Affiliation: DISPAA, University of Florence, Viale delle Idee 30, 50019 Sesto Fiorentino, Italy ; HSO-USB, ESTEC, European Space Agency, Keplerlaan 1, 2200 AG Noordwijk, The Netherlands.

ABSTRACT
Oxygen influx showed an asymmetry in the transition zone of the root apex when roots were placed horizontally on ground. The influx increased only in the upper side, while no changes were detected in the division and in the elongation zone. Nitric oxide (NO) was also monitored after gravistimulation, revealing a sudden burst only in the transition zone. In order to confirm these results in real microgravity conditions, experiments have been set up by using parabolic flights and drop tower. The production of reactive oxygen species (ROS) was also monitored. Oxygen, NO, and ROS were continuously monitored during normal and hyper- and microgravity conditions in roots of maize seedlings. A distinct signal in oxygen and NO fluxes was clearly detected only in the apex zone during microgravity, with no significant changes in normal and in hypergravity conditions. The same results were obtained by ROS measurement. The detrimental effect of D'orenone, disrupting the polarised auxin transport, on the onset of the oxygen peaks during the microgravity period was also evaluated. Results indicates an active role of NO and ROS as messengers during the gravitropic response, with probable implications in the auxin redistribution.

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Related in: MedlinePlus

Respiration rate in roots incubated in D'orenone for the different groups related to the oxygen concentration in the solution.
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fig7: Respiration rate in roots incubated in D'orenone for the different groups related to the oxygen concentration in the solution.

Mentions: Interesting results have been also obtained from the measurement of the respiration rate by oximeters. The respiration rate inside a single parabola has been divided into five segments, each segment being related to a different gravity level: 1 g, 2 g, 0 g, 2 g (after microgravity), and 1 g (after microgravity). Negative values indicate oxygen influx. Respiration by root apices led to an unavoidable reduction of the oxygen content in the solution due to the plant metabolism; thus the parabolas have been divided into different groups by taking into account the real oxygen concentration because the respiration rate is directly related to the amount of oxygen present in the solution. Four groups related to different [O2] in the solution have been therefore created: >1500 nM, 1000–1500 nM, 500–1000 nM, and <500 nM. The values relative to the control (Figure 6) show no significant differences among the different gravity levels in each parabola for every oxygen concentration group, except for the last group ([O2] < 500 nM) with an increased respiration rate during the second period of hypergravity. On the contrary, the presence of D'orenone in the solution did not lead to any variation neither in the respiration rate among the different gravity levels nor compared to the control (Figure 7). D'orenone has been utilized in this experiment because it increases PIN2 protein abundance without affecting PIN2 transcripts, with the consequence that the PIN2 expression domain enlarges and shifts basipetally, resulting in more active auxin transport. To deeply analyse the previous results, the behaviour of the respiration rate during a single parabola has been evaluated. It has been noted that when [O2] was < 700 nM, a sudden burst of oxygen was produced only in the control a few seconds after the onset of microgravity (Figure 8). This large amount of oxygen was quickly absorbed by the roots for respiration, thus explaining the increased respiration rate during the second hypergravity period. This phenomenon was clearly evident during each parabola with [O2] < 700 nM. The fact that the bursts were evident only when [O2] < 700 nM was probably due to the electrode sensitivity, which was not able to discriminate very low differences in the respiration rate (around 25 nM) with higher oxygen concentrations in the solution. These oxygen bursts have been characterised by calculating the area inside the curve (Figure 9). The values of area, response time after the onset of microgravity, peak duration, and peak amplitude are reported in Figure 10, with a discrimination based on the parabolas' groups. No significant differences among the groups were noted in the peak area, with an average value of 274.73 nM representing the moles of oxygen produced during the microgravity period and then consumed, in the response time after the onset of microgravity (average value of 0.79 seconds) and the timing of the maximum peak (11.03 seconds). On the contrary, significant differences among groups were registered in the peak duration. The first 20 parabolas had an average peak duration of 20-21 seconds, while the last 10 parabolas had a longer duration (average value around 30 seconds). Finally, peak amplitude showed no significant differences. As expected, when no roots were present in the oximeter, a stable signal was registered (data not shown).


Oxidative stress and NO signalling in the root apex as an early response to changes in gravity conditions.

Mugnai S, Pandolfi C, Masi E, Azzarello E, Monetti E, Comparini D, Voigt B, Volkmann D, Mancuso S - Biomed Res Int (2014)

Respiration rate in roots incubated in D'orenone for the different groups related to the oxygen concentration in the solution.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4150467&req=5

fig7: Respiration rate in roots incubated in D'orenone for the different groups related to the oxygen concentration in the solution.
Mentions: Interesting results have been also obtained from the measurement of the respiration rate by oximeters. The respiration rate inside a single parabola has been divided into five segments, each segment being related to a different gravity level: 1 g, 2 g, 0 g, 2 g (after microgravity), and 1 g (after microgravity). Negative values indicate oxygen influx. Respiration by root apices led to an unavoidable reduction of the oxygen content in the solution due to the plant metabolism; thus the parabolas have been divided into different groups by taking into account the real oxygen concentration because the respiration rate is directly related to the amount of oxygen present in the solution. Four groups related to different [O2] in the solution have been therefore created: >1500 nM, 1000–1500 nM, 500–1000 nM, and <500 nM. The values relative to the control (Figure 6) show no significant differences among the different gravity levels in each parabola for every oxygen concentration group, except for the last group ([O2] < 500 nM) with an increased respiration rate during the second period of hypergravity. On the contrary, the presence of D'orenone in the solution did not lead to any variation neither in the respiration rate among the different gravity levels nor compared to the control (Figure 7). D'orenone has been utilized in this experiment because it increases PIN2 protein abundance without affecting PIN2 transcripts, with the consequence that the PIN2 expression domain enlarges and shifts basipetally, resulting in more active auxin transport. To deeply analyse the previous results, the behaviour of the respiration rate during a single parabola has been evaluated. It has been noted that when [O2] was < 700 nM, a sudden burst of oxygen was produced only in the control a few seconds after the onset of microgravity (Figure 8). This large amount of oxygen was quickly absorbed by the roots for respiration, thus explaining the increased respiration rate during the second hypergravity period. This phenomenon was clearly evident during each parabola with [O2] < 700 nM. The fact that the bursts were evident only when [O2] < 700 nM was probably due to the electrode sensitivity, which was not able to discriminate very low differences in the respiration rate (around 25 nM) with higher oxygen concentrations in the solution. These oxygen bursts have been characterised by calculating the area inside the curve (Figure 9). The values of area, response time after the onset of microgravity, peak duration, and peak amplitude are reported in Figure 10, with a discrimination based on the parabolas' groups. No significant differences among the groups were noted in the peak area, with an average value of 274.73 nM representing the moles of oxygen produced during the microgravity period and then consumed, in the response time after the onset of microgravity (average value of 0.79 seconds) and the timing of the maximum peak (11.03 seconds). On the contrary, significant differences among groups were registered in the peak duration. The first 20 parabolas had an average peak duration of 20-21 seconds, while the last 10 parabolas had a longer duration (average value around 30 seconds). Finally, peak amplitude showed no significant differences. As expected, when no roots were present in the oximeter, a stable signal was registered (data not shown).

Bottom Line: The same results were obtained by ROS measurement.The detrimental effect of D'orenone, disrupting the polarised auxin transport, on the onset of the oxygen peaks during the microgravity period was also evaluated.Results indicates an active role of NO and ROS as messengers during the gravitropic response, with probable implications in the auxin redistribution.

View Article: PubMed Central - PubMed

Affiliation: DISPAA, University of Florence, Viale delle Idee 30, 50019 Sesto Fiorentino, Italy ; HSO-USB, ESTEC, European Space Agency, Keplerlaan 1, 2200 AG Noordwijk, The Netherlands.

ABSTRACT
Oxygen influx showed an asymmetry in the transition zone of the root apex when roots were placed horizontally on ground. The influx increased only in the upper side, while no changes were detected in the division and in the elongation zone. Nitric oxide (NO) was also monitored after gravistimulation, revealing a sudden burst only in the transition zone. In order to confirm these results in real microgravity conditions, experiments have been set up by using parabolic flights and drop tower. The production of reactive oxygen species (ROS) was also monitored. Oxygen, NO, and ROS were continuously monitored during normal and hyper- and microgravity conditions in roots of maize seedlings. A distinct signal in oxygen and NO fluxes was clearly detected only in the apex zone during microgravity, with no significant changes in normal and in hypergravity conditions. The same results were obtained by ROS measurement. The detrimental effect of D'orenone, disrupting the polarised auxin transport, on the onset of the oxygen peaks during the microgravity period was also evaluated. Results indicates an active role of NO and ROS as messengers during the gravitropic response, with probable implications in the auxin redistribution.

Show MeSH
Related in: MedlinePlus