Journal Article

Genes and gene clusters related to genotype and drought-induced variation in saccharification potential, lignin content and wood anatomical traits in <i>Populus nigra</i>

Henning Wildhagen, Shanty Paul, Mike Allwright, Hazel K Smith, Marta Malinowska, Sabine K Schnabel, M João Paulo, Federica Cattonaro, Vera Vendramin, Simone Scalabrin, Dennis Janz, Cyril Douthe, Oliver Brendel, Cyril Buré, David Cohen, Irène Hummel, Didier Le Thiec, Fred van Eeuwijk, Joost J B Keurentjes, Jaume Flexas, Michele Morgante, Paul Robson, Marie-Béatrice Bogeat-Triboulot, Gail Taylor and Andrea Polle

in Tree Physiology

Volume 38, issue 3, pages 320-339
Published in print March 2018 | ISSN: 0829-318X
Published online May 2017 | e-ISSN: 1758-4469 | DOI: https://dx.doi.org/10.1093/treephys/tpx054

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Abstract

Wood is a renewable resource that can be employed for the production of second generation biofuels by enzymatic saccharification and subsequent fermentation. Knowledge on how the saccharification potential is affected by genotype-related variation of wood traits and drought is scarce. Here, we used three Populus nigra L. genotypes from habitats differing in water availability to (i) investigate the relationships between wood anatomy, lignin content and saccharification and (ii) identify genes and co-expressed gene clusters related to genotype and drought-induced variation in wood traits and saccharification potential. The three poplar genotypes differed in wood anatomy, lignin content and saccharification potential. Drought resulted in reduced cambial activity, decreased vessel and fiber lumina, and increased the saccharification potential. The saccharification potential was unrelated to lignin content as well as to most wood anatomical traits. RNA sequencing of the developing xylem revealed that 1.5% of the analyzed genes were differentially expressed in response to drought, while 67% differed among the genotypes. Weighted gene correlation network analysis identified modules of co-expressed genes correlated with saccharification potential. These modules were enriched in gene ontology terms related to cell wall polysaccharide biosynthesis and modification and vesicle transport, but not to lignin biosynthesis. Among the most strongly saccharification-correlated genes, those with regulatory functions, especially kinases, were prominent. We further identified transcription factors whose transcript abundances differed among genotypes, and which were co-regulated with genes for biosynthesis and modifications of hemicelluloses and pectin. Overall, our study suggests that the regulation of pectin and hemicellulose metabolism is a promising target for improving wood quality of second generation bioenergy crops. The causal relationship of the identified genes and pathways with saccharification potential needs to be validated in further experiments.

Keywords: biofuels; cell wall; drought; genotypic variation; glucose release; lignin; Populus; saccharification; wood traits

Journal Article.  11954 words.  Illustrated.

Subjects: Plant Sciences and Forestry