Different evolutionary pathways to generate plant fructan exohydrolases

Fructans are fructose-based oligo- and polysaccharides serving as a carbohydrate reserve but also acting as prebiotics and potential signaling molecules. More than two decades ago, the scientific community first hypothesized that plant fructan exohydrolases (FEHs) could have evolved from vacuolar invertases, since plant fructans reside in the vacuole. However, it was found that FEHs resembled cell wall invertases instead. Oku et al. (2022) have now characterized a novel fructan 1-exohydrolase (1-FEH) from onion, an economically important species. This enzyme fits well within the vacuolar invertase subgroup, demonstrating that plant FEHs may be recruited from different types of ancestral invertases. This finding will inspire further research into the evolution of plant FEHs in general, shedding more light on their puzzling functions in both fructan-accumulating and non-fructan-accumulating plants.

Automated summary

Researchers have discovered a novel fructan 1-exohydrolase (1-FEH) in onions, which belongs to the vacuolar invertase subgroup and suggests that plant fructan exohydrolases could have originated from different ancestral invertases. This finding will contribute to further understanding the evolution and functions of plant FEHs in fructan-accumulating and non-fructan-accumulating plants.