Analysis of pectin mutants and natural accessions of Arabidopsis highlights the impact of de-methyl-esterified homogalacturonan on tissue saccharification.
BACKGROUND
Plant biomass is a potentially important renewable source of energy and industrial products. The natural recalcitrance of the cell walls to enzymatic degradation (saccharification), which plants have evolved to defend themselves from biotic stresses, represents a major bottleneck for the industrial bioconversion of lignocellulosic biomasses. The identification of factors that influence the cell wall recalcitrance to saccharification may help to overcome the existing limitations that hamper the utilization of biomass.


RESULTS
Here we have investigated in Arabidopsis thaliana the impact of homogalacturonan (HG) content and structure on tissue saccharification. We characterized mutants affected in genes encoding proteins involved in HG biosynthesis (quasimodo2-1; qua2-1) and methylesterification (pectin methylesterase 3; pme3). We also analyzed the natural variation of Arabidopsis through the characterization of a nested core collection of 24 accessions generated to maximize genetic variability. We found a negative correlation between the level of de-methyl-esterified HG (HGA) and cellulose degradability.


CONCLUSIONS
We propose to use the level of HGA domains as a biochemical marker of the cell wall recalcitrance to saccharification. This may be utilized for selecting, on a large scale, natural variants or mutants with improved bioconversion features.
Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Piazzale Aldo Moro 5, Rome 00185, Italy.
Fedra
F
Francocci
Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Piazzale Aldo Moro 5, Rome 00185, Italy.
Elisa
E
Bastianelli
Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Piazzale Aldo Moro 5, Rome 00185, Italy.
Vincenzo
V
Lionetti
Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Piazzale Aldo Moro 5, Rome 00185, Italy.
Simone
S
Ferrari
Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Piazzale Aldo Moro 5, Rome 00185, Italy.
Giulia
G
De Lorenzo
Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Piazzale Aldo Moro 5, Rome 00185, Italy.
Daniela
D
Bellincampi
Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Piazzale Aldo Moro 5, Rome 00185, Italy.
Felice
F
Cervone