Multi-target genome editing reduces polyphenol oxidase activity in wheat ( L.) grains.

Introduction: Polyphenol oxidases (PPO) are dual activity metalloenzymes that catalyse the production of quinones. In plants, PPO activity may contribute to biotic stress resistance and secondary metabolism but is undesirable for food producers because it causes the discolouration and changes in flavour profiles of products during post-harvest processing. In wheat ( L.

Genomic-based epidemiology reveals independent origins and gene flow of glyphosate resistance in Bassia scoparia populations across North America.

Genomic-based epidemiology can provide insight into the origins and spread of herbicide resistance mechanisms in weeds. We used kochia (Bassia scoparia) populations resistant to the herbicide glyphosate from across western North America to test the alternative hypotheses that (i) a single EPSPS gene duplication event occurred initially in the Central Great Plains and then subsequently spread to all other geographical areas now exhibiting glyphosate-resistant kochia populations or that (ii) gene duplication occurred multiple times in independent events in a case of parallel evolution. We used qPCR markers previously developed for measuring the structure of the EPSPS tandem duplication to investigate whether all glyphosate-resistant individuals had the same EPSPS repeat structure.

Reduced free asparagine in wheat grain resulting from a natural deletion of TaASN-B2: investigating and exploiting diversity in the asparagine synthetase gene family to improve wheat quality.

Background: Understanding the determinants of free asparagine concentration in wheat grain is necessary to reduce levels of the processing contaminant acrylamide in baked and toasted wheat products. Although crop management strategies can help reduce asparagine concentrations, breeders have limited options to select for genetic variation underlying this trait. Asparagine synthetase enzymes catalyse a critical step in asparagine biosynthesis in plants and, in wheat, are encoded by five homeologous gene triads that exhibit distinct expression profiles.

Extensive structural variation in the Bowman-Birk inhibitor family in common wheat (Triticum aestivum L.).

Background: Bowman-Birk inhibitors (BBI) are a family of serine-type protease inhibitors that modulate endogenous plant proteolytic activities during different phases of development. They also inhibit exogenous proteases as a component of plant defense mechanisms, and their overexpression can confer resistance to phytophagous herbivores and multiple fungal and bacterial pathogens. Dicot BBIs are multifunctional, with a "double-headed" structure containing two separate inhibitory loops that can bind and inhibit trypsin and chymotrypsin proteases simultaneously.

The power and potential of genomics in weed biology and management.

There have been previous calls for, and efforts focused on, realizing the power and potential of weed genomics for better understanding of weeds. Sustained advances in genome sequencing and assembly technologies now make it possible for individual research groups to generate reference genomes for multiple weed species at reasonable costs. Here, we present the outcomes from several meetings, discussions, and workshops focused on establishing an International Weed Genomics Consortium (IWGC) for a coordinated international effort in weed genomics.

Effects of EPSPS Copy Number Variation (CNV) and Glyphosate Application on the Aromatic and Branched Chain Amino Acid Synthesis Pathways in .

A key enzyme of the shikimate pathway, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS; EC 2.5.1.

A Program for Iron Economy during Deficiency Targets Specific Fe Proteins.

Iron (Fe) is an essential element for plants, utilized in nearly every cellular process. Because the adjustment of uptake under Fe limitation cannot satisfy all demands, plants need to acclimate their physiology and biochemistry, especially in their chloroplasts, which have a high demand for Fe. To investigate if a program exists for the utilization of Fe under deficiency, we analyzed how hydroponically grown Arabidopsis () adjusts its physiology and Fe protein composition in vegetative photosynthetic tissue during Fe deficiency.

Glyphosate Resistance and EPSPS Gene Duplication: Convergent Evolution in Multiple Plant Species.

One of the increasingly widespread mechanisms of resistance to the herbicide glyphosate is copy number variation (CNV) of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene. EPSPS gene duplication has been reported in 8 weed species, ranging from 3 to 5 extra copies to more than 150 extra copies. In the case of Palmer amaranth (Amaranthus palmeri), a section of >300 kb containing EPSPS and many other genes has been replicated and inserted at new loci throughout the genome, resulting in significant increase in total genome size.

Regulation of Cu delivery to chloroplast proteins.

Plastocyanin is a copper (Cu)-requiring protein that functions in photosynthetic electron transport in the thylakoid lumen of plants. To allow plastocyanin maturation, Cu must first be transported into the chloroplast stroma by means of the PAA1/HMA6 transporter and then into the thylakoid lumen by the PAA2/HMA8 transporter. Recent evidence indicated that the chloroplast regulates Cu transport into the thylakoids via Clp protease-mediated turnover of PAA2/HMA8.

Prioritization of copper for the use in photosynthetic electron transport in developing leaves of hybrid poplar.

Plastocyanin (PC) is an essential and abundant copper (Cu) protein required for photosynthesis in higher plants. Severe copper deprivation has the potential to cause a defect in photosynthetic electron transport due to a lack in PC. The Cu-microRNAs, which are up-regulated under Cu deficiency, down-regulate the expression of target Cu proteins other than PC, cytochrome-c oxidase and the ethylene receptors.

Copper and iron homeostasis in plants: the challenges of oxidative stress.

Significance: Photosynthesis, the process that drives life on earth, relies on transition metal (e.g., Fe and Cu) containing proteins that participate in electron transfer in the chloroplast.

Plastocyanin controls the stabilization of the thylakoid Cu-transporting P-type ATPase PAA2/HMA8 in response to low copper in Arabidopsis.

PAA2/HMA8 (P-type ATPase of Arabidopsis/Heavy-metal-associated 8) is a thylakoid located copper (Cu)-transporter in Arabidopsis thaliana. In tandem with PAA1/HMA6, which is located in the inner chloroplast envelope, it supplies Cu to plastocyanin (PC), an essential cuproenzyme of the photosynthetic machinery. We investigated whether the chloroplast Cu transporters are affected by Cu addition to the growth media.

Iron and ROS control of the DownSTream mRNA decay pathway is essential for plant fitness.

A new regulatory pathway involved in plant response to oxidative stress was revealed using the iron-induced Arabidopsis ferritin AtFER1 as a model. Using pharmacological and genetic approaches, the DownSTream (DST) cis-acting element in the 3'-untranslated region of the AtFER1 mRNA was shown to be involved in the degradation of this transcript, and oxidative stress triggers this destabilization. In the two previously identified trans-acting mutants (dst1 and dst2), AtFER1 mRNA stability is indeed impaired.

Spatiotemporal analysis of copper homeostasis in Populus trichocarpa reveals an integrated molecular remodeling for a preferential allocation of copper to plastocyanin in the chloroplasts of developing leaves.

Plastocyanin, which requires copper (Cu) as a cofactor, is an electron carrier in the thylakoid lumen and essential for photoautotrophic growth of plants. The Cu microRNAs, which are expressed during Cu deprivation, down-regulate several transcripts that encode for Cu proteins. Since plastocyanin is not targeted by the Cu microRNAs, a cofactor economy model has been proposed in which plants prioritize Cu for use in photosynthetic electron transport.

The biogenesis and physiological function of chloroplast superoxide dismutases.

Iron-superoxide dismutase (FeSOD) and copper/zinc-superoxide dismutase (Cu/ZnSOD) are evolutionarily conserved proteins in higher plant chloroplasts. These enzymes are responsible for the efficient removal of the superoxide formed during photosynthetic electron transport and function in reactive oxygen species metabolism. The availability of copper is a major determinant of Cu/ZnSOD and FeSOD expression.

Ferritins and iron storage in plants.

Iron is essential for both plant productivity and nutritional quality. Improving plant iron content was attempted through genetic engineering of plants overexpressing ferritins. However, both the roles of these proteins in the plant physiology, and the mechanisms involved in the regulation of their expression are largely unknown.

New insights into ferritin synthesis and function highlight a link between iron homeostasis and oxidative stress in plants.

Background: Iron is an essential element for both plant productivity and nutritional quality. Improving plant iron content was attempted through genetic engineering of plants overexpressing ferritins. However, both the roles of these proteins in plant physiology, and the mechanisms involved in the regulation of their expression are largely unknown.

Essential transition metal homeostasis in plants.

The homeostasis of the essential transition metals copper, iron, manganese and zinc requires balanced activities of transporters that mediate import into the cell, distribution to organelles and export from the cell. Transcriptional control is important for the regulation of cellular homeostasis. In the case of Fe and Cu much progress has been made in uncovering the regulatory networks that mediate homeostasis, and key transcription factors have now been described.

Ferritins control interaction between iron homeostasis and oxidative stress in Arabidopsis.

Ferritin protein nanocages are the main iron store in mammals. They have been predicted to fulfil the same function in plants but direct evidence was lacking. To address this, a loss-of-function approach was developed in Arabidopsis.

Knock-out of ferritin AtFer1 causes earlier onset of age-dependent leaf senescence in Arabidopsis.

Ferritins are iron-storage proteins involved in the regulation of free iron levels in the cells. Arabidopsis thaliana AtFer1 ferritin, one of the best characterized plant ferritin isoforms to date, strongly accumulates upon treatment with excess iron, via a nitric oxide-mediated pathway. However other environmental factors, such as exposure to oxidative stress or to pathogen attack, as well as developmental factors regulate AtFer1 transcript levels.

The iron-responsive element (IRE)/iron-regulatory protein 1 (IRP1)-cytosolic aconitase iron-regulatory switch does not operate in plants.

Animal cytosolic ACO (aconitase) and bacteria ACO are able to switch to RNA-binding proteins [IRPs (iron-regulatory proteins)], thereby playing a key role in the regulation of iron homoeostasis. In the model plant Arabidopsis thaliana, we have identified three IRP1 homologues, named ACO1-3. To determine whether or not they may encode functional IRP proteins and regulate iron homoeostasis in plants, we have isolated loss-of-function mutants in the three genes.