Human survival is dependent on plant mitochondria and chloroplasts. These crucial plant cell compartments are well-known for collecting sunlight and fueling plant life, providing all the food we eat. However, there's a minor catch the Mitochondria and chloroplasts store instructions for their building blocks in their own 'organelle' DNA, or oDNA, that can be changed.
Mild consequences of this could be observed in some 'variegated' plants, where the leaves get bleached and lose their power to photosynthesise. This effect could be beautiful in your garden however bad for crops.
How do plants prevent the accumulation of mutational harm over time? To understand the entire topic, the University of Bergen and Colorado State University collaborated, and surprisingly, the answer is found partly by exploiting randomness.
Generating diversity with randomness
Suppose a plant inherits some mutation from its mother and transmits the same mutation onto each offspring. In that case, mutations will eventually build up over generations and the plant's descendants will die off.
Plants instead spread out the harm they inherit, such that while some offspring receive many mutations, others acquire significantly fewer. This process, which occurs in animals and humans, is known as segregation. It also relies on the plant producing random variances in its offspring.
"The segregation process is known to be very fast in humans and has a big effect on the inheritance of human genetic diseases," said Dan Sloan, the head of the Colorado research team. "Remarkably, we've found that it's even faster in plants."
Agricultural implications
"Our work is really exciting because until now, we had very little information about how these mutations behave in plants," added Amanda Broz, first author on the study. "Agricultural scientists have recently become interested in understanding variation in oDNA because mitochondria and chloroplasts are so critically essential to plant growth and yield; our results are good news for crop breeders wanting to introduce new beneficial mutations."
Researchers generated plants with high mutations
To understand the segregation of oDNA, the team generated plants that inherited high levels of mutations and tracked how these mutations were distributed through the plant over time. They then used mathematical and statistical modelling to translate these experimental observations into theory, describing how the plant was randomly spreading its inherited damage. They found that a combination of processes, random distribution of oDNA when cells divide and random overwriting of some oDNA molecules with others, could explain all their observations of plant segregation over time and from mothers to daughters.
They also found some support for the idea that plants 'set aside' some cells early in their lives that will end up responsible for producing the next generation, an idea currently actively debated in plant science.
"I've dreamed for years of exploring this process," said Iain Johnston, corresponding author and leader of the Bergen research team. "It's the combination of these beautiful new plant lines, detailed experiments, and modern maths and statistics that have made it possible."
Team research backs the latest ideas
The team's results support recent theories about how many other lifeforms maintain their power plants and could be a step towards manipulating oDNA in plants, an essential aspect of crop breeding and yield enhancement. The European Research Council, the National Science Foundation, and the Peder Sather Fund supported the research.
(With inputs from ANI)
