Abstract
Lignin is a plant biopolymer that is highly concentrated in so-called lignified cell walls and represents a major component in lignocellulosic plant biomass. Although lignified cell walls can be found in all kinds of vegetative and reproductive plant organs, cell wall lignification is pronounced within the wood tissue, which is developed by a lateral meristem (vascular cambium) and is responsible for most of the lateral stem and root growth in woody shrubs and trees. In flowering plants, hundreds of non-woody (herbaceous) lineages independently gave rise to new woody species, suggesting that: i) woodiness provides a fitness advantage in (seasonally) dry environments, and ii) only few genetic key regulatory changes are required for the transition from herb to shrub. Interestingly, lignin production in herbaceous stems can also be enhanced in response to drought stress, where it is assumed to strengthen cell walls, facilitate root-to-shoot water transport, and impede water loss. As such, increased lignin deposition in plant cell walls as well as increased wood formation in stems and roots have been suggested by a range of pilot studies as a key strategy for drought tolerance during plant evolution. Drought tolerance is currently a key trait in crop breeding, as traditionally productive agricultural areas suffer heavily from recurring and more intensive drought cycles across the globe. At the same time, as lignified wood tissue is a major constituent of agricultural residues, scientists should take advantage of its value in the biobased economy in terms of residue valorisation. Indeed, lignin has high potential in applications such as glues and asphalt, meaning that increased lignin content provides opportunities for replacement of fossil derived products by left-over plant parts of more drought resilient crops. In this project we will investigate more in-depth how stem woodiness or lignification enhance plant drought tolerance. We aim to answer three fundamental questions: 1) What are the gene regulatory networks that control lignification and/or wood formation in stems of three carefully selected species of flowering plants with accessions with varying degrees of woodiness, and can we disentangle the woodiness phenotype from coupled phenotypes, such as late flowering? 2) What are the advantages of increased woodiness or lignification in terms of drought resilience both in the short term (adaptation) and in the long term (evolution)? 3) What is the relationship between the lignin chemical structure, the cell wall structure of lignified tissue and drought tolerance, and how does that influence utilisation of stems as biobased material in left-over plant parts? In order to do this, we have established a novel multidisciplinary consortium uniquely bridging expertise in plant anatomy, evolution, development, physiology, genetics, molecular biology and lignin chemistry. With promising genetic key regulators for woodiness and lignification at hand and a comprehensive understanding of factors determining lignin quality, we anticipate fundamental scientific breakthroughs and impactful future applications for a more sustainable agriculture.
Netherlands