Engineering plants tolerant to the toxic proline mimic azetidine-2-carboxylic acid through co-option of a bacterial detoxification mechanism

Azetidine-2-carboxylic acid (Aze) is a dangerous, non-proteinogenic amino acid that can contaminate our food and cause brain damage due to its tendency to substitute for proline during protein synthesis. While some bacteria have developed ways to break down Aze, these methods have never been used to make plants resistant to this toxic substance.

In a new study, scientists inserted a bacterial enzyme called HAS into Arabidopsis thaliana plants to create a process for plants to tackle Aze. When the transgenic plants were exposed to Aze, they showed better root growth, healthier cotyledon development, and greater survival rates when compared to regular plants. The HAS enzyme was found to be located in the plant cells' cytosol, where it converted Aze into a harmless compound called 2-hydroxy-4-aminobutyrate (HAB).

Tests in both plants and a lab setting confirmed that HAS kept working and effectively neutralized Aze. The enzyme was also found to be very selective for L-Aze and showed no activity toward its mirror image, D-Aze. By studying the plants' gene activity and protein production, researchers discovered that the transgenic plants incorporated less Aze, which helped them tolerate the toxin better.

This research demonstrates that the bacterial HAS enzyme can be used as a successful method to make plants resistant to toxic non-proteinogenic amino acids like Aze, potentially providing a new approach to protect crops from harmful contaminants.