Growth–defense trade‐offs and yield loss in plants with engineered cell walls

Abstract

As a major component of plant secondary cell walls, lignin provides structural integrity and rigidity, and contributes to primary defense by providing a physical barrier to pathogen ingress. Genetic modification of lignin biosynthesis has been adopted to reduce the recalcitrance of lignified cell walls to improve biofuel production, tree pulping properties and forage digestibility. However, lignin-modification is often, but unpredictably, associated with dwarf phenotypes. Hypotheses suggested to explain this include: collapsed vessels leading to defects in water and solute transport; accumulation of molecule(s) that are inhibitory to plant growth or deficiency of metabolites that are critical for plant growth; activation of defense pathways linked to cell wall integrity sensing. However, there is still no commonly accepted underlying mechanism for the growth defects. Here, we discuss recent data on transcriptional reprogramming in plants with modified lignin content and their corresponding suppressor mutants, and evaluate growth-defense trade-offs as a factor underlying the growth phenotypes. New approaches will be necessary to estimate how gross changes in transcriptional reprogramming may quantitatively affect growth. Better understanding of the basis for yield drag following cell wall engineering is important for the biotechnological exploitation of plants as factories for fuels and chemicals.

CRISPR‐Cas9 editing of CAFFEOYL SHIKIMATE ESTERASE 1 and 2 shows their importance and partial redundancy in lignification in Populus tremula × P. alba

“…The vessel cell morphology is compromised in cse1 cse2 lines, as observed in several other plants with perturbations in the lignin biosynthetic pathway (Coleman et al ., 2008; Jones et al ., 2001; Leplé et al ., 2007; Schilmiller et al ., 2009; Vanholme et al ., 2013c; Voelker et al ., 2010). This is a possible reason for the observed yield penalty, either because the function of the vessel cell wall is impaired or because its physico‐chemical defects signal a stress response (Gallego‐Giraldo et al ., 2020; Gallego‐Giraldo et al ., 2018; Ha et al ., 2021; Muro‐Villanueva et al ., 2019); restoring lignification in the vessel cells of Arabidopsis lignin mutants has been successfully used to recover the vessel cell morphology and overall biomass, while still maintaining the enhanced saccharification efficiency of the mutant biomass (De Meester et al ., 2018; Vargas et al ., 2016; Yang et al ., 2013). However, implementing this strategy in trees might not be straightforward to rescue the biomass yield penalty.…”

Rice miR1432 Fine-Tunes the Balance of Yield and Blast Disease Resistance via Different Modules

“…Growth-defense tradeoffs are thought to occur because of resource restrictions, and hormone crosstalk acted as a major player in regulating the balance of tradeoffs (Huot et al 2014 ). Moreover, transcriptional reprogramming of the immunity-associated genes in plants often reduces plant growth and yield (Ha et al 2021 ). Whether OsEFH1 regulated rice panicle development via these CDPK or hormone signaling, or the transcriptional reprogramming is unknown and needs further study.…”

Behind the Scenes: The Impact of Bioactive Phenylpropanoids on the Growth Phenotypes of Arabidopsis Lignin Mutants

“…The central role of the PPP in plant secondary metabolism implies its involvement in a plethora of processes. Genetic or chemical perturbations therefore often come with a variety of phenotypic defects ( Ha et al, 2021 ) of which the severity is frequently linked to the degree of perturbation and the level of genetic redundancy. The different phenotypes range from overall dwarfism to more distinct phenotypes such as increased or decreased lateral rooting, increased shoot branching, male sterility, and a decreased seed set.…”