Cell wall targeted in planta iron accumulation enhances biomass conversion and seed iron concentration in Arabidopsis and rice.

Haibing Yang,Wendy A Peer,Mauricio S Antunes,Michael E Himmel,Xiping Liu,Stefan Vogt,Guojie Ma,Lintao Bu,Xiao Zhang,Joseph Cox,Lee Makowski,Angus S Murphy,S Charlotte Gleber,Melvin P Tucker,Nicholas C Carpita,Maureen C Mccann,Hui Wei

doi:10.1111/pbi.12557

Abstract

SummaryConversion of nongrain biomass into liquid fuel is a sustainable approach to energy demands as global population increases. Previously, we showed that iron can act as a catalyst to enhance the degradation of lignocellulosic biomass for biofuel production. However, direct addition of iron catalysts to biomass pretreatment is diffusion‐limited, would increase the cost and complexity of biorefinery unit operations and may have deleterious environmental impacts. Here, we show a new strategy for in planta accumulation of iron throughout the volume of the cell wall where iron acts as a catalyst in the deconstruction of lignocellulosic biomass. We engineered CBM‐IBP fusion polypeptides composed of a carbohydrate‐binding module family 11 (CBM11) and an iron‐binding peptide (IBP) for secretion into Arabidopsis and rice cell walls. CBM‐IBP transformed Arabidopsis and rice plants show significant increases in iron accumulation and biomass conversion compared to respective controls. Further, CBM‐IBP rice shows a 35% increase in seed iron concentration and a 40% increase in seed yield in greenhouse experiments. CBM‐IBP rice potentially could be used to address iron deficiency, the most common and widespread nutritional disorder according to the World Health Organization.

Highlights

As the world population continues to increase and fossil resources are finite, alternative feedstocks for fuels and other chemicals are being developed to meet this growing demand (Hill et al, 2006)
Translation of Ni2+ hyperaccumulation mechanisms to Fe2+, Cu2+ and Mn2+ accumulation is limited as cytosolic Fe2+, Cu2+ and Mn2+ levels required for effective cell wall catalysis are toxic to living plants
Two iron-binding peptides (IBP) were synthesized and analysed for metal binding: a minimal ferritin-binding peptide based on the ferritin monomer and a synthetic iron-binding motif based on the blood iron-binding peptide that we had previously isolated and found that it bound iron across a wide range of pH

Summary

Conversion of nongrain biomass into liquid fuel is a sustainable approach to energy demands as global population increases. We showed that iron can act as a catalyst to enhance the degradation of lignocellulosic biomass for biofuel production. Direct addition of iron catalysts to biomass pretreatment is diffusion-limited, would increase the cost and complexity of biorefinery unit operations and may have deleterious environmental impacts. We show a new strategy for in planta accumulation of iron throughout the volume of the cell wall where iron acts as a catalyst in the deconstruction of lignocellulosic biomass. We engineered CBM-IBP fusion polypeptides composed of a carbohydrate-binding module family 11 (CBM11) and an iron-binding peptide (IBP) for secretion into Arabidopsis and rice cell walls. CBM-IBP transformed Arabidopsis and rice plants show significant increases in iron accumulation and biomass conversion compared to respective controls. CBM-IBP rice shows a 35% increase in seed iron concentration and a 40% increase in seed yield in greenhouse experiments.

Introduction

Results and discussion

Experimental procedures