Plant Hormones: The Mystery of Beta-Carotene's Role

Plants have a clever way of responding to their environment. They use special chemicals called hormones. Two of these, abscisic acid and strigolactones, come from a substance called beta-carotene. Abscisic acid helps plants handle drought and keeps seeds from sprouting too early. Strigolactones, on the other hand, are made when nutrients are scarce. They control how plants branch out and even help some plants germinate by tricking parasites. Both of these hormones start from beta-carotene. They go through similar steps to become what they are. One key step is an isomerization reaction, where the shape of a molecule is changed. An enzyme called D27 helps with this in strigolactones. But for abscisic acid, the enzyme doing this job is still a mystery. Arabidopsis thaliana, a small plant often used in research, has two versions of the D27 enzyme, called D27LIKE1 and D27LIKE2. D27LIKE1 seems to do some of what D27 does. But D27LIKE2? Its job is still unknown. To figure this out, scientists created plants with one, two, or all three of these genes removed. They then studied how these plants grew and made hormones. The results were surprising. These genes seem to work together to make strigolactones. This means they can be turned on and off as needed in different plant parts. However, these genes don't seem to help make abscisic acid. This is a big deal. It shows that these enzyme versions are picky. They only help make strigolactones, not abscisic acid. This could change how we think about how plants make these important hormones.