New research finds evolutionary missing link between pollen and bacteria

Plants and bacteria diverged billions of years ago, but a new study at Washington University claims to have found the missing link between the two.

In the study, Dr. Elizabeth Haswell, associate professor of biology at the university, illustrates that an ancient protein, called MSL8, is critical to reproduction. According to a news release, The protein is responsible for regulating pressure during pollen’s potentially problematic rehydration process.

The discovery was made after an undergraduate in Haswell’s lab noticed that dry pollen without the MSL8 safety protein burst as a result of taking in water too quickly. Without the protein, the reproductive tubes in pollen rupture due to the pressure that powers their growth.

Pollen loses hydration during maturation, causing it to enter a state of suspended animation. During the reproductive process, pollen becomes rehydrated by sugary fluids secreted by the female organs of a flower.

The way in which the protein regulates pressure within the pollen, acting as a sort of safety valve, is highly reminiscent of the way in which bacteria uses stretch-activated channels to relieve excessive internal pressure.

The bacterial channel protects the bacteria from random environmental stress,” Dr. Haswell said. “In the pollen a related channel is also protecting the cell, but from stresses it must withstand in order to reproduce.”

Additionally, bacteria and pollen are similar in the sense that they are both single celled organisms without support from a mother plant. Dr. Haswell points out that, although there are billions of years of evolution between them, pollen and bacteria use similar stretch-activated safety cells as a means of regulating internal pressure.

“The study indicates how important mechanical signals are in biology,” Haswell said. “They are not just signals from the environment, but also signals that are part of normal developmental processes. Mechanotransduction is important to every aspect of an organism’s life.”



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