# Investigation of Arabidopsis root skototropism with different distance settings

## TL;DR

This study explores how Arabidopsis roots respond to darkness by bending, and how this behavior changes with distance from the light source.

## Contribution

The study reveals the weakening of positive skototropism with increased distance and identifies GLR3.7 and PIN2 as key players in this process.

## Key findings

- Root positive skototropism weakens as the distance from darkness increases.
- GLR3.7 and PIN2 are involved in root skototropic behavior.
- Different Arabidopsis lines show varied root bending tendencies under skototropism.

## Abstract

Plants can activate protective and defense mechanisms under biotic and abiotic stresses. Their roots naturally grow in the soil, but when they encounter sunlight in the top-soil layers, they may move away from the light source to seek darkness. Here we investigate the skototropic behavior of roots, which promotes their fitness and survival. Glutamate-like receptors (GLRs) of plants play roles in sensing and responding to signals, but their role in root skototropism is not yet understood. Light-induced tropisms are known to be affected by auxin distribution, mainly determined by auxin efflux proteins (PIN proteins) at the root tip. However, the role of PIN proteins in root skototropism has not been investigated yet. To better understand root skototropism and its connection to the distance between roots and light, we established five distance settings between seedlings and darkness to investigate the variations in root bending tendencies. We compared differences in root skototropic behavior across different expression lines of Arabidopsis thaliana seedlings (atglr3.7 ko, AtGLR3.7 OE, and pin2 knockout) to comprehend their functions. Our research shows that as the distance between roots and darkness increases, the root’s positive skototropism noticeably weakens. Our findings highlight the involvement of GLR3.7 and PIN2 in root skototropism.