Lignin is an aromatic biopolymer involved in providing structural support to plant cell walls. Compared to the other cell wall polymers, i.e., cellulose and hemicelluloses, lignin has been considered a hindrance in cellulosic bioethanol production due to the complexity involved in its separation from other polymers of various biomass feedstocks. Nevertheless, lignin is a potential source of valuable aromatic chemical compounds and upgradable building blocks. Though the biosynthetic pathway of lignin has been elucidated in great detail, the random nature of the polymerization (free radical coupling) process poses challenges for its depolymerization into valuable bioproducts. The absence of specific methodologies for lignin degradation represents an important opportunity for research and development. This review highlights research development in lignin biosynthesis, lignin genetic engineering and different biological and chemical means of depolymerization used to convert lignin into biofuels and bioproducts.

The mechanisms underlying the biosynthesis of cellulose in plants are complex and still poorly understood. A central question concerns the mechanism of microfibril structure and how this is linked to the catalytic polymerization action of cellulose synthase (CESA). Furthermore, it remains unclear whether modification of cellulose microfibril structure can be achieved genetically, which could be transformative in a bio-based economy. To explore these processes in planta , we developed a chemical genetic toolbox of pharmacological inhibitors and corresponding resistance-conferring point mutations in the C-terminal transmembrane domain region of CESA1 ^A903V and CESA3 ^T942I in Arabidopsis thaliana . Using ¹³ C solid-state nuclear magnetic resonance spectroscopy and X-ray diffraction, we show that the cellulose microfibrils displayed reduced width and an additional cellulose C4 peak indicative of a degree of crystallinity that is intermediate between the surface and interior glucans of wild type, suggesting a difference in glucan chain association during microfibril formation. Consistent with measurements of lower microfibril crystallinity, cellulose extracts from mutated CESA1 ^A903V and CESA3 ^T942I displayed greater saccharification efficiency than wild type. Using live-cell imaging to track fluorescently labeled CESA, we found that these mutants show increased CESA velocities in the plasma membrane, an indication of increased polymerization rate. Collectively, these data suggest that CESA1 ^A903V and CESA3 ^T942I have modified microfibril structure in terms of crystallinity and suggest that in plants, as in bacteria, crystallization biophysically limits polymerization.

Mechanisms involved in the biological control of plant diseases are varied and complex. Hormones, including the auxin indole acetic acid (IAA) and abscisic acid (ABA), are essential regulators of a multitude of biological functions, including plant responses to biotic and abiotic stressors. This study set out to determine what hormones might play a role in Pseudomonas fluorescens –mediated control of Fusarium head blight (FHB) disease of barley and to determine if biocontrol-associated hormones directly affect disease development.

The use of phytoremediation to sustainably recover areas contaminated by toxic heavy metals such as cadmium (Cd) has been made feasible since the discovery of hyperaccumulator plants. This study examines the potential of the invasive Impatiens glandulifera for phytoremediation propensity of Cd. In these experiments, the plants were exposed to and tested for Cd accumulation; the propensity to accumulate other heavy metals, such as Zinc, was not investigated. The efficacy of phytoaccumulation was assessed over two trials (Cd concentrations of 20 mg/kg to 150 mg/kg) via examination of bioconcentration factor (BCF), translocation factor (TF), and total removal (TR). Exposure to Cd levels of up to 150 mg/kg in the trials did not affect the biomass of the plants compared to the control. Impatiens glandulifera accumulated cadmium at a rate of 276 to 1562 mg/kgin stems, with BCFs, TFs, and TRs of 64.6 to 236.4, 0.2 to 1.2, and 3.6 to 29.2 mg Cd, respectively. In vitro germination revealed unprecedented germination ability, demonstrating the remarkable hypertolerance of I. glandulifera, with no significant difference in the germination of seedlings exposed to 1000 mg/kg Cd compared to the control. This study also examined the localization of Cd in plant tissues via a histochemical assay using dithizone. The results presented herein suggest that I. glandulifera can act as a hyperaccumulator of Cd for phytoremediation.