By Shao-Li Yang and Chin-Min Kimmy Ho
Background: The plant epidermis is composed of functionally specialized cells, such as the valves on the leaf surface known as stomata, and is covered by the cuticle to prevent water loss. When stomata are open to take in CO2 for photosynthesis, water evaporates from the leaf. Therefore, stomata and the cuticle are two important characters for terrestrialization, a critical event in which organisms moved from the ocean to the land. Several studies have uncovered the link between stomatal patterning and cuticle development. However, the underlying mechanism was not clear.
Question: How is cuticle formation integrated with stomatal development during leaf morphogenesis? We addressed this question by misregulating MYB16, a positive controller of cuticle development.
Findings: We observed that MYB16 was preferentially expressed in cells that did not become guard cells (a pair of guard cells form a stomate). This observation suggested that stomatal cells prevent cuticle accumulation during the early stage of leaf development. When we forced MYB16 to be expressed in stomatal cells, an increased stomatal number and an abnormal stomatal pattern were observed. We further found that the polarity protein that is required for the correct stomatal fate was mis-orientated. These results indicate that producing the cuticle too early during development altered the mechanical properties of the leaf epidermis and led to incorrect stomatal patterning.
Next steps: Finding the downstream genes of MYB16 will help us understand the formation of the leaf cuticle. Our results provide a strategy to modulate the cuticle and stomatal number on the leaf epidermis to improve crop growth and production in adverse environments.
Shao-Li Yang, Ngan Tran, Meng-Ying Tsai and Chin-Min Kimmy Ho (2022). Misregulation of MYB16 expression causes stomatal cluster formation by disrupting polarity during asymmetric cell divisions. Plant Cell. https://doi.org/10.1093/plcell/koab260