Friends in Arms: Flavonoids and the Auxin/Cytokinin Balance in Terrestrialization.

Land plants survive the challenges of new environments by evolving mechanisms that protect them from excess irradiation, nutrient deficiency, and temperature and water availability fluctuations. One such evolved mechanism is the regulation of the shoot/root growth ratio in response to water and nutrient availability by balancing the actions of the hormones auxin and cytokinin. Plant terrestrialization co-occurred with a dramatic expansion in secondary metabolism, particularly with the evolution and establishment of the flavonoid biosynthetic pathway.

Differential oxidative stress responses and tobacco-specific nitrosamine accumulation in two burley varieties.

Tobacco-specific nitrosamines (TSNAs) are carcinogens that accumulate in tobacco leaves during curing, storage, and processing, and their amounts in processed tobacco vary dependent on several intrinsic and extrinsic factors. Here, we assessed the hypothesis that there is a link between reactive oxygen species levels in leaves and TSNA formation during curing. First, we show that burley varieties KT 204LC and NCBH 129LC accumulate TSNAs to different levels but not as a result of a variety-specific abundance of TSNA precursors.

Inhibition of f. sp. Growth by Phenylpropanoid Pathway Intermediates.

Fusarium wilt in tobacco caused by the fungus f. sp. is a disease‑management challenge worldwide, as there are few effective and environmentally benign chemical agents for its control.

Cytokinin-induced protein synthesis suppresses growth and osmotic stress tolerance.

Cytokinins control critical aspects of plant development and environmental responses. Perception of cytokinin ultimately leads to the activation of proteins belonging to the type-B Response Regulator family of cytokinin response activators. In Arabidopsis thaliana, ARR1 is one of the most abundantly expressed type-B Response Regulators.

Metabolomic analyses of the bio-corona formed on TiO nanoparticles incubated with plant leaf tissues.

Background: The surface of a nanoparticle adsorbs molecules from its surroundings with a specific affinity determined by the chemical and physical properties of the nanomaterial. When a nanoparticle is exposed to a biological system, the adsorbed molecules form a dynamic and specific surface layer called a bio-corona. The present study aimed to identify the metabolites that form the bio-corona around anatase TiO nanoparticles incubated with leaves of the model plant Arabidopsis thaliana.

Anatase TiO Nanoparticles Induce Autophagy and Chloroplast Degradation in Thale Cress ().

The extensive use of TiO nanoparticles and their subsequent release into the environment have posed an important question about the effects of this nanomaterial on ecosystems. Here, we analyzed the link between the damaging effects of reactive oxygen species generated by TiO nanoparticles and autophagy, a housekeeping mechanism that removes damaged cellular constituents. We show that TiO nanoparticles induce autophagy in the plant model system and that autophagy is an important mechanism for managing TiO nanoparticle-induced oxidative stress.

Antagonistic activity of auxin and cytokinin in shoot and root organs.

The hormones auxin and cytokinin are essential for plant growth and development. Because of the central importance of root and shoot apical meristems in plant growth, auxin/cytokinin interactions have been predominantly analyzed in relation to apical meristem formation and function. In contrast, the auxin/cytokinin interactions during organ growth have remained largely unexplored.

Modulation of auxin and cytokinin responses by early steps of the phenylpropanoid pathway.

Background: The phenylpropanoid pathway is responsible for the synthesis of numerous compounds important for plant growth and responses to the environment. In the first committed step of phenylpropanoid biosynthesis, the enzyme phenylalanine ammonia-lyase (PAL) deaminates L-phenylalanine into trans-cinnamic acid that is then converted into p-coumaric acid by cinnamate-4-hydroxylase (C4H). Recent studies showed that the Kelch repeat F-box (KFB) protein family of ubiquitin ligases control phenylpropanoid biosynthesis by promoting the proteolysis of PAL.

Cytokinin signaling promotes differential stability of type-B ARRs.

Cytokinins control key aspects of plant growth, including shoot and root meristem development and the timing of senescence of leaves and stems. Cytokinin perception triggers a 2-component signaling mechanism that ultimately leads to phosphorylation-dependent activation of a class of transcriptional regulators called type-B ARRs (RRBs). We have recently shown that the stability of the RRB family member ARR1 is increased in response to elevated cytokinin concentrations.