The nucleus follows an internal cellular scale during polarized root hair cell development

The root hair cell is a product of asymmetric cell division, which grows in a polar manner, and thus is an attractive model cell type from a cellular biology aspect. Beyond the fundamental cell biology context, the root hair is involved in water and nutrient acquisition, making it important for agronomic applications. Nuclear positioning in the cell is crucial during root hair development. Often, textbooks demonstrate illustrations of the nucleus located at a fixed position from the tip of a root hair or at the very end of a root hair. The fundamental question is whether the nucleus follows a cellular scale during polarized growth. Maintaining the scale is a rudimentary biological process during development at the organismal and cellular levels. In this study, we altered root hairs through hormonal, nutrient, and environmental factors to decipher the cellular scale (no scale, universal scale, or internal scale) maintained by the nucleus. We utilized the live cell imaging combined with a quantitative cell biology approach and, surprisingly discovered that the nucleus always follows an internal scale in the root hair cell. This finding dramatically shifted our view about the nuclear position in a polarized cell and will have a potential to test across the tree of life. Altogether, understanding the cellular scale involved with nucleus positioning will have broad implications. It encourages a reexamination of textbooks and reinforces the agricultural importance in a changing climate.