A novel FC17/CESA4 mutation causes increased biomass saccharification and lodging resistance by remodeling cell wall in rice

Fengcheng Li,Quan Xu,Hai Xu,Sitong Liu

doi:10.1186/s13068-018-1298-2

Fengcheng Li, Quan Xu + Show 2 more

Open Access

https://doi.org/10.1186/s13068-018-1298-2

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Abstract

BackgroundRice not only produces grains for human beings, but also provides large amounts of lignocellulose residues, which recently highlighted as feedstock for biofuel production. Genetic modification of plant cell walls can potentially enhance biomass saccharification; however, it remains a challenge to maintain a normal growth with enhanced lodging resistance in rice.ResultsIn this study, rice (Oryza sativa) mutant fc17, which harbors the substitution (F426S) at the plant-conserved region (P-CR) of cellulose synthase 4 (CESA4) protein, exhibited slightly affected plant growth and 17% higher lodging resistance compared to the wild-type. More importantly, the mutant showed a 1.68-fold enhancement in biomass saccharification efficiency. Cell wall composition analysis showed a reduction in secondary wall thickness and cellulose content, and compensatory increase in hemicelluloses and lignin content. Both X-ray diffraction and calcofluor staining demonstrated a significant reduction in cellulose crystallinity, which should be a key factor for its high saccharification. Proteomic profiling of wild-type and fc17 plants further indicated a possible mechanism by which mutation induces cellulose deposition and cell wall remodeling.ConclusionThese results suggest that CESA4 P-CR site mutation affects cell wall features especially cellulose structure and thereby causes enhancement in biomass digestion and lodging resistance. Therefore, CESA4 P-CR region is promising target for cell wall modification to facilitate the breeding of bioenergy rice.

Highlights

Rice produces grains for human beings, and provides large amounts of lignocellulose residues, which recently highlighted as feedstock for biofuel production
We report on a novel cellulose synthase 4 (CESA4) conserved site mutation that leads to increased lignocellulose enzymatic hydrolysis and lodging resistance by reducing cellulose Crystallinity index (CrI) and remodeling cell wall
The fc17 mutant has a brittleness phenotype caused by a CESA4 conserved site mutation A fragile culm 17 mutant was isolated from a natural population of the Japonica cultivar ShenNong265 (Fig. 1a)

Summary

Introduction

Rice produces grains for human beings, and provides large amounts of lignocellulose residues, which recently highlighted as feedstock for biofuel production. Genetic modification of plant cell walls can potentially enhance biomass saccharification; it remains a challenge to maintain a normal growth with enhanced lodging resistance in rice. Plant cell walls are essential for plant growth and development and provide renewable biomass feedstock for biofuels production [1]. Genetic modifications of wall polymers have been applied to enhance biomass saccharification [2,3,4]. Plant cells are surrounded by a strong yet adaptable primary cell wall, which is mainly composed of cellulose, hemicelluloses, pectins, and proteins [6]. Through intra- and inter-chain hydrogen bonding, parallel linear glucan chains are crystalized to form cellulose microfibrils that provide plants with excellent toughness for normal plant growth [1]

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