Gravity affects sex in plants
12 Apr 2013 by Evoluted New Media
Changes in gravity affect reproduction in plants, reveals a University of Montreal study. Their findings, published in PLOS ONE, offer new insight into how life evolved on Earth.
Gravity was found to modulate the vesicle traffic that ensures the growth and functionality of plant pollen tubes – the male reproductive organ. Within the pollen tube cells, an intracellular transport system transports vesicles of cell wall material in the direction of the growing tube for the continuous assembly of the structure.
“Researchers already knew that humans, animals and plants have evolved in response to Earth’s gravity and that they are able to sense it. What we are still discovering is how the processes occurring within the cells of humans and plants are affected by the more intense gravity, or hypergravity that would be found on a large planet, or the microgravity that resembles the conditions on a space craft,” said Professor Anja Geitmann from the University’s Department of Botany.
Intracellular transport processes are particularly sensitive to disturbances which can have dramatic consequence for the functions of the cell. But how these processes are affected by a change in gravity is poorly understood.
To combat this, the team decided to study pollen tubes because of their extraordinary rapid growth which would enable the researchers to observe the effects of hyper gravity within seconds.
The scientists placed pollen tube cells from camellias into the Large Diameter Centrifuge at the European Space Agency, with a camera attached to a microscope. This enabled the researchers to track in real time how the cells were developing in the intense gravity generated by the centrifuge.
To study microgravity, the researchers exposed the pollen tubes to conditions that resemble zero gravity, by placing them in a Random Positioning Machine at the ESTE.
The team stained for vesicles within the cells to reveal how cellular trafficking responds to the changing gravity environment.
The researchers were able to demonstrate that vesicular trafficking is reduced under hyper-gravity and micro-gravity conditions. They say a possible explanation for this effect is that in response to gravity induced stress, the pollen tube responds by modifying cell well assembly to compensate for the altered mechanical load.
They also found that the effect was reversible within a few minutes demonstrating the pollen tube has evolved to quickly adapt to changing stress conditions.
Dr Youssef Chebli, a researcher in Geitmann’s lab said: “This work allows us not only to understand general principles of the reproductive mechanism in plants but, more importantly, how the intracellular transport machinery in eukaryotic cells responds to altered gravity conditions. Our findings have implications for human health as similar effects are likely to occur in human cells such as neurons where long distance intracellular transport is crucial.”
