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In plant cells, as in other cells, genetic information is stored within structures known as chromosomes. Most of the cells in a plant contain a duplicated set of chromosomes that the plant needs to survive. However, plants also produce some cells known as sex cells that only have a single set of chromosomes. This ensures that, when plants sexually reproduce, a male and female sex cell will fuse together and eventually grow into a new plant that carries a doubled set of chromosomes.
Cells known as meiocytes make sex cells by dividing through a process known as meiosis. Previous studies have identified several genes that regulate meiosis in plants. For example, a gene known as TAM is required to make sex cells in a small weed known as Arabidopsis thaliana, which is often used as a model plant in research studies.
During meiosis, meiocytes need to copy and move their chromosomes at precisely the right time to ensure that each sex cell they produce has a complete set of chromosomes. Studies of how chromosomes behave during meiosis in plants have so far almost exclusively relied on traditional microscopy techniques that kill the cells in the process of preparing them for imaging. Before being placed under a microscope, the dead cell material is often spread out to make it easier to see the chromosomes. These techniques provide snapshots of meiosis that provide good spatial resolution of chromosome behavior, but information about how chromosomes and other cellular components behave in the course of meiosis is lost.
Prusicki et al. developed a new microscopy approach to observe meiosis in living A. thaliana cells. The experiments found that the structure of all the cells changed during meiosis in several distinct stages (referred to as ‘landmarks’). Some of these landmarks were absent or happened at a different time in mutant plant cells that lacked the TAM gene. As a result, a structure called the spindle that is required to move chromosomes during meiosis formed at the wrong time in the mutant cells.
The findings of Prusicki et al. reveal new insights into the role of TAM in meiosis. The next step following on from this work is to use the same approach to study other mutant plants with defects in meiosis and analyze the effects of a changing environment on meiosis.