Mystery solved: how plant cells know when to stop growing

This is an A long-term mystery in biology: how do cells know how big they are?

It turns out that the answer is hidden in Robert Sablowski’s computer files, who have been collecting virtual dust since 2013. “I have had this data for years, but I didn’t look for it in the right way,” said Sablowski, a plant cell biologist at the John Innes Center in Norwich, England. In an early project, he has been working on a protein called KRP4. By fusing it with fluorescent jellyfish protein to make it glow, Sablowski can study it in plant cells, but he didn’t know that this would be the key to understanding cell size regulation.

For organisms to develop, their cells must undergo a pattern of growth, DNA replication, and division. But scientists who study this process (called the cell cycle) have long noticed that divisions are not necessarily the same-cells usually divide asymmetrically, and their size is later corrected in some way.in a Research published in science Last month, Sablowski and his colleagues revealed how plants do this: cells use their own DNA as a kind of measuring cup.Although this discovery was made by researching something called Arabidopsis, It may have a wide-ranging impact on the understanding of cell size regulation in animals and humans, and may even affect the future of crop production.

Determining how a cell evaluates its size has always been complicated, because most cellular proteins change with the size of the cell itself. Sablowski compares this situation to trying to measure himself with his arm. “You can’t do this because your arms grow in proportion to your body,” he said. “You need an external reference to know how old you are.” However, what does not change as the cell grows is its DNA. Scientists have long speculated that cells can use their DNA as an indicator to measure their size, but Sablowski’s team was the first to prove this process.

“Biology has been a deep mystery for decades, how cells can accomplish this task, knowing their size almost magically,” said Martin Howard of the John Innes Center, who helped develop the required mathematical models. breakthrough. Shape and size adjustment are important because they are closely related to the function of the cell: too large, the cell may have difficulty quickly retrieving the information contained in its own DNA; too small, the cell does not have enough space to divide properly, leading to division and growth errors May cause disease.

Arabidopsis According to Sablovsky, it is actually a weed, but it is considered a model organism in plant biology because it grows easily and matures quickly. This means that other researchers in the field have already conducted in-depth research on it. “The community is Arabidopsis It’s always been crucial,” said Marco D’Ario, a graduate student at the John Innes Center who designed and helped execute the experiment. 15 years. “

Team growth Arabidopsis Leave it in the pot for about six weeks, then cut off the tiny growth tips of the plant, that is, the part where new leaves and flowers appear, and observe its continued growth under a microscope. They can track the position and size of each cell in the growth tip at different stages of the cell cycle at a magnification of approximately 1,000 times. Sablowski and D’Ario changed shifts, inspecting the cells every hour for two days. “We have the equipment, we have the materials. We only need to roll up our sleeves and conduct 48-hour experiments to get data that no one else has,” Sablovsky said.