Exposing enzymes
It was proposed that CSE functioned in the monolignol pathway in Arabidopsis thaliana in 2014, indicating that loss of function of CSE leads to a reduction in lignin content and a small decrease in plant growth, although the phenotypes are much less severe than in those observed with loss of function of the two preceding enzymes in the lignin pathway in Arabidopsis. Since then, the role of CSE in lignin biosynthesis has been questioned in several species, in part through the inability to demonstrate the activity of the enzyme. The pathway via CSE is certainly counter-intuitive, as it involves the cleavage of a thioester linkage and its subsequent re-formation, involving the hydrolysis of an extra molecule of ATP.
Shedding light on the role of caffeoyl shikimate esterase (CSE) in lignin biosynthesis in different plants
An essential role of caffeoyl shikimate esterase in monolignol biosynthesis in Medicago truncatula The Plant Journal, Vol 86, pages 363–375, Ha, Chan Man; Escamilla-Tresino, Luis; Serrani Yarce, Juan Carlos ; Kim, Hoon; Ralph, John; Chen, Fang; Dixon, Richard
http://onlinelibrary.wiley.com/doi/10.1111/tpj.13177/abstract
It was proposed that CSE functioned in the monolignol pathway in Arabidopsis thaliana in 2014, indicating that loss of function of CSE leads to a reduction in lignin content and a small decrease in plant growth, although the phenotypes are much less severe than in those observed with loss of function of the two preceding enzymes in the lignin pathway in Arabidopsis. Since then, the role of CSE in lignin biosynthesis has been questioned in several species, in part through the inability to demonstrate the activity of the enzyme. The pathway via CSE is certainly counter-intuitive, as it involves the cleavage of a thioester linkage and its subsequent re-formation, involving the hydrolysis of an extra molecule of ATP. In this manuscript Ha et al. showed the presence of CSE genes and associated enzyme activity in barrel medic (Medicago truncatula, dicot, Leguminosae), poplar (Populus deltoides, dicot, Salicaceae), and switchgrass (Panicum virgatum, monocot, Poaceae), shedding important insight into monolignol biosythesis in the context of CSE function and how its role in lignification differs significantly among species. By examining the presence of CSE genes in the genomes of 61 plant species, both monocot and dicot, they showed that its role in lignification differs from totally dispensable (Brachypodium) through significantly involved (Arabidopsis) to critically involved (Medicago). These results provide clarity to the role of an enzyme whose function has not been previously universally accepted.
Jim Ruddock, Managing Editor
