Arabidopsis Acetyl Xylan Esterase (AXE) overexpression improves lignocellulosic biomass digestibility

Xylan O-acetylation is critical for stable interaction with cellulose and other polymers in the cell wall. Its alteration improves cellulose as well as xylan digestibility. Xylan acetyl pool is regulated by Golgi and membrane localized esterase but they are not well characterized in plants. In this study, we have identified and characterized first plasma membrane localized xylan acetyl esterase and showed that its overexpression improves digestibility of polysaccharide.

In our study, initially, we tested the expression of selected members from the AtGELP family in AtMYB46 overexpressor (OE) lines which is a well-known regulator of xylan biosynthesis. AtGELP7 expression was 55 fold higher in 35S::AtMYB46 lines suggesting that it could be involved in xylan de- esterification. To test this, we further generated three independent OE transgenic lines of AtGELP7, which showed an increase in AXE activity and a decrease in xylan acetylation as compared to wild-type plants. We confirmed its AXE activity by heterologously expressing AtGELP7 in E. Coli. Immunoblot and confocal studies showed that the AtGELP7 is associated with the plasma membrane and its extracellular catalytic domain is performing de-esterification of xylan which might be necessary for stable xylan-cellulose interactions or cell wall recycling. More importantly, Arabidopsis lines expressing AtGELP7 exhibited efficient cellulose and xylan digestibility suggesting that it could be an attractive target for lignocellulosic biomass improvement in other bioenergy crops.

Rastogi et al., 2022. “Arabidopsis GELP7 Functions as a Plasma Membrane ‑ Localized Acetyl Xylan Esterase , and Its Overexpression Improves Saccharification Efficiency.” Plant Molecular Biology, 109, pages 781–797 (2022)