Pattern

---

Pattern

The stomata in the leaf of a plant are more or less equally distributed. They are forming a pattern. But not at the moment of germination, then there are no stomata. Afterwards they are formed supper quickly. Researchers from America now discovered that already during embryo development this stomata pattern is being formed.

The stomata of a plant are the results of series of well-ordered cell divisions. These result in the end in two cells that together enclose an opening in the leave, forming the stomata. The managers of this process are SPEACHLESS, which takes care of the first half of the process, and MUTE and FAMA, who together regulate the second part.

Although an embryo does not contain any stomata, its managers are present. This gave the researchers the idea to study what these stomata managers are doing in the embryo. To be able to see what these managers were doing in the embryo, the researchers attached to them a fluorescent protein.

In this way the researchers noticed that SPEACHLESS was active early on during embryo development. In the beginning in groups of cells, located where the embryogenic leaves develop. But with the maturation of the embryo SPEACHLESS was more and more located in single cells surrounded by cells that did not had any SPEACHLESS.

---

Without the early influence of SPEACHLESS the plant loses its overview of its stomata

---

In contrast to SPEACHLESS, of the managers of the second half of stomata development only MUTE was seen, and only at the end of embryo development. Then MUTE was seen in the same cells in which SPEACHLESS was observed. From FAMA, needed for the final step in stomata development, no trace was seen. The stomata developed only partially during embryo development.

Even though the stomata are not developing completely, the pattern these pre-stomata form is important. In seedlings in which SPEACHLESS could not do its job during embryo development, the researchers noticed that stomata are formed in clusters. The stomata were not equally distributed on the leaf.

The early activity of SPEACHLESS during embryo development enables the plant to develop an equally distributed stomata pattern. Without the early influence of SPEACHLESS this did not work. Then the plant loses its overview. Then the stomata become clustered.

Literature

Margot E. Smit, Anne Vatén, Andrea Mair, Carrie A.M. Northover, and Dominique C. Bergmann (2023) Extensive embryonic patterning without cellular differentiation primes the plant epidermis for efficient post-embryonic stomatal activities, Developmental Cell (2023), https://doi.org/10.1016/j.devcel.2023.02.014