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Heterologous overexpression of Arabidopsis cellulase 1 (Atcel1) results in enhanced yield, early maturity, and increased biomass in dicotyledonous species like poplar and eucalyptus but has not been demonstrated in monocots. We produced transgenic Setaria viridis accession A10.1 plants overexpressing a monocotyledonous codon optimized (MCO) Atcel1. Agronomic characterization of the transgenic events showed that heterologous overexpression of MCOAtcel1 caused enhanced grain yield, shoot biomass, and accelerated maturation rate in the model grass species S. viridis under growth chamber conditions. The agronomic trait differences observed were consistent with previous reports in dicots but are here described in a monocot species and associated with increased seed yield. Overexpression of Atcel1 in S. viridis was shown to increase the number of panicles and seeds by 24–30%, enhance overall grain yield by up to 26%, and lead to a shoot dry biomass increase of 16–19%. Overexpression also reduced time to plant maturation and senescence by 12.5%. Our findings in S. viridis suggest that manipulation of Atcel1 has potential for developing early-maturing and higher-yielding monocotyledonous biomass crops suitable for climate-smart agriculture. [ABSTRACT FROM AUTHOR]

SUMMARY: In recent years, Setaria viridis has been developed as a model plant to better understand the C4 photosynthetic pathway in major crops. With the increasing availability of genomic resources for S. viridis research, highly efficient genome editing technologies are needed to create genetic variation resources for functional genomics. Here, we developed a protoplast assay to rapidly optimize the multiplexed clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR‐associated (Cas9) system in S. viridis. Targeted mutagenesis efficiency was further improved by an average of 1.4‐fold with the exonuclease, Trex2. Distinctive mutation profiles were found in the Cas9_Trex2 samples, with 94% of deletions larger than 10 bp, and essentially no insertions at all tested target sites. Further analyses indicated that 52.2% of deletions induced by Cas9_Trex2, as opposed to 3.5% by Cas9 alone, were repaired through microhomology‐mediated end joining (MMEJ) rather than the canonical non‐homologous end joining DNA repair pathway. Combined with a robust Agrobacterium‐mediated transformation method with more than 90% efficiency, the multiplex CRISPR/Cas9_Trex2 system was demonstrated to induce targeted mutations in two tightly linked genes, svDrm1a and svDrm1b, at a frequency ranging from 73% to 100% in T0 plants. These mutations were transmitted to at least 60% of the transgene‐free T1 plants, with 33% of them containing bi‐allelic or homozygous mutations in both genes. This highly efficient multiplex CRISPR/Cas9_Trex2 system makes it possible to create a large mutant resource for S. viridis in a rapid and high throughput manner, and has the potential to be widely applicable in achieving more predictable and deletion‐only MMEJ‐mediated mutations in many plant species. Significance Statement: Setaria viridis has recently emerged as an attractive monocot model species to better understand C4 photosynthesis and accelerate functional genomics research in the grasses. Highly efficient genome editing technologies are much needed to greatly expedite the process of genetic manipulation and gene discovery in S. viridis. [ABSTRACT FROM AUTHOR]

The present study reveals contrasting responses of photosynthesis to salt stress in two C4 species: a glycophyte Setaria viridis (SV) and a halophyte Spartina alterniflora (SA). Specifically, the effect of short-term salt stress treatment on the photosynthetic CO2 uptake and electron transport were investigated in SV and its salt-tolerant close relative SA. In this experiment, at the beginning, plants were grown in soil then were exposed to salt stress under hydroponic conditions for two weeks. SV demonstrated a much higher susceptibility to salt stress than SA; while, SV was incapable to survive subjected to about 100 mM, SA can tolerate salt concentrations up to 550 mM with slight effect on photosynthetic CO2 uptake rates and electrons transport chain conductance (gETC). Regardless the oxygen concentration used, our results show an enhancement in the P700 oxidation with increasing O2 concentration for SV following NaCl treatment and almost no change for SA. We also observed an activation of the cyclic NDH-dependent pathway in SV by about 2.36 times upon exposure to 50 mM NaCl for 12 days (d); however, its activity in SA drops by about 25% compared to the control without salt treatment. Using PTOX inhibitor (n-PG) and that of the Qo-binding site of Cytb6/f (DBMIB), at two O2 levels (2 and 21%), to restrict electrons flow towards PSI, we successfully revealed the presence of a possible PTOX activity under salt stress for SA but not for SV. However, by q-PCR and western-blot analysis, we showed an increase in PTOX amount by about 3–4 times for SA under salt stress but not or very less for SV. Overall, this study provides strong proof for the existence of PTOX as an alternative electron pathway in C4 species (SA), which might play more than a photoprotective role under salt stress. [ABSTRACT FROM AUTHOR]

Background Model organisms are at the core of life science research. Notable examples include the mouse as a model for humans, baker's yeast for eukaryotic unicellular life and simple genetics, or the enterobacteria phage λ in virology. Plant research was an exception to this rule, with researchers relying on a variety of non-model plants until the eventual adoption of Arabidopsis thaliana as primary plant model in the 1980s. This proved to be an unprecedented success, and several secondary plant models have since been established. Currently, we are experiencing another wave of expansion in the set of plant models. Scope Since the 2000s, new model plants have been established to study numerous aspects of plant biology, such as the evolution of land plants, grasses, invasive and parasitic plant life, adaptation to environmental challenges, and the development of morphological diversity. Concurrent with the establishment of new plant models, the advent of the 'omics' era in biology has led to a resurgence of the more complex non-model plants. With this review, we introduce some of the new and fascinating plant models, outline why they are interesting subjects to study, the questions they will help to answer, and the molecular tools that have been established and are available to researchers. Conclusions Understanding the molecular mechanisms underlying all aspects of plant biology can only be achieved with the adoption of a comprehensive set of models, each of which allows the assessment of at least one aspect of plant life. The model plants described here represent a step forward towards our goal to explore and comprehend the diversity of plant form and function. Still, several questions remain unanswered, but the constant development of novel technologies in molecular biology and bioinformatics is already paving the way for the next generation of plant models. [ABSTRACT FROM AUTHOR]

The need for atmospheric carbon dioxide (CO2) reduction in the context of global warming is widely acknowledged by the global scientific community. Fossil fuel CO2 (CO2ff) emissions occur mainly in cities, and can be monitored directly with radiocarbon (14C). In this research, annual plants [Setaria viridis (L.) Beauv.] were collected from 26 sites in 2013 and 2014 in the central urban district of Xi'an City. The Δ14C content of the samples were analyzed using a 3 MV Accelerator Mass Spectrometer, and CO2ff concentrations were calculated based on mass balance equations. The results showed that the CO2ff mixing ratio ranged from 15.9 to 25.0 ppm (part per million, equivalent to µmol mol−1), with an average of 20.5 ppm in 2013. The range of measured values became larger in 2014, from 13.9 ppm to 33.1 ppm, with an average of 23.5 ppm. The differences among the average CO2ff concentrations between the central area and outer urban areas were not statistically significant. Although the year-to-year variation of the CO2ff concentration was significant (P < 0.01), there was a distinctly low CO2ff value observed in the northeast corner of the city. CO2ff emissions from vehicle exhaust and residential sources appeared to be more significant than two thermal power plants, according to our observed CO2ff spatial distribution. The variation of pollution source transport recorded in our observations was likely controlled by southwesterly winds. These results could assist in the optimal placement of regional CO2 monitoring stations, and benefit the local government in the implementation of efficient carbon emission reduction measures. [ABSTRACT FROM AUTHOR]

Paspalum urvillei and Setaria parviflora are two plant species naturally adapted to iron-rich environments such as around iron mines wastes. The aim of our work was to characterize how these two species cope with these extreme conditions by comparing them with related model species, Oryza sativa and Setaria viridis, that appeared to be much less tolerant to Fe excess. Both Paspalum urvillei and Setaria parviflora were able to limit the amount of Fe accumulated within roots and shoots, compared to the less tolerant species. Perls/DAB staining of Fe in root cross sections indicated that Paspalum urvillei and Setaria parviflora responded through the build-up of the iron plaque (IP), suggesting a role of this structure in the limitation of Fe uptake. Synchrotron μXRF analyses showed the presence of phosphorus, calcium, silicon and sulfur on IP of Paspalum urvillei roots and μXANES analyses identified Fe oxyhydroxide (ferrihydrite) as the main Fe form. Once within roots, high concentrations of Fe were localized in the cell walls and vacuoles of Paspalum urvillei , Setaria parviflora and O. sativa whereas Setaria viridis accumulated Fe in ferritins. The Fe forms translocated to the shoots of Setaria parviflora were identified as tri-iron complexes with citrate and malate. In leaves, all species accumulated Fe in the vacuoles of bundle sheath cells and as ferritin complexes in plastids. Taken together, our results strongly suggest that Paspalum urvillei and Setaria parviflora set up mechanisms of Fe exclusion in roots and shoots to limit the toxicity induced by Fe excess. • Paspalum urvillei and Setaria parviflora are two species naturally adapted to iron-rich environments. • These two species are more tolerant to Fe excess than the model, related species Oryza sativa and Setaria viridis. • Tolerance to Fe excess is achieved by exclusion: formation of iron plaque and vacuolar storage in roots. • The iron plaque is composed mostly of ferrihydrite; Fe is translocated in xylem as tri-Fe citrate-malate complexes. [ABSTRACT FROM AUTHOR]

Setaria viridis (green foxtail) has been identified as a potential experimental model system to genetically and molecularly characterise the C4 monocotyledonous grasses due to its small physical size, short generation time and prolific seed production, together with a sequenced and annotated genome. Setaria viridis is the wild ancestor of the cropping species, foxtail millet (Setaria italica), with both Setaria species sharing a close evolutionary relationship with the agronomically important species, maize, sorghum, and sugarcane, as well as the bioenergy feedstocks, switchgrass, and Miscanthus. However, an efficient and reproducible transformation protocol is required to further advance the use of S. viridis to study the molecular genetics of C4 monocotyledonous grasses. An efficient and reproducible protocol was established for Agrobacterium tumefaciens -mediated transformation of S. viridis (Accession A10) regenerable callus material derived from mature seeds, a protocol that returned an average transformation efficiency of 6.3%. The efficiency of this protocol was the result of the: (i) use of mature embryo derived callus material; (ii) age of the seed used to induce callus formation; (iii) composition of the callus induction media, including the addition of the ethylene inhibitor, silver nitrate; (iv) use of a co-cultivation approach, and; (v) concentration of the selective agent. Our protocol furthers the use of S. viridis as an experimental model system to study the molecular genetics of C4 monocotyledonous grasses for the potential future development of improved C4 cropping species. [ABSTRACT FROM AUTHOR]

Although sugar regulates photosynthesis, the signalling pathways underlying this process remain elusive, especially for C4 crops. To address this knowledge gap and identify potential candidate genes, we treated Setaria viridis (C4 model) plants acclimated to medium light intensity (ML, 500 µmol m−2 s−1) with low (LL, 50 µmol m−2 s−1) or high (HL, 1000 µmol m−2 s−1) light for 4 d and observed the consequences on carbon metabolism and the transcriptome of source leaves. LL impaired photosynthesis and reduced leaf content of signalling sugars (glucose, sucrose, and trehalose-6-phosphate). In contrast, HL strongly induced sugar accumulation without repressing photosynthesis. LL more profoundly impacted the leaf transcriptome, including photosynthetic genes. LL and HL contrastingly altered the expression of hexokinase (HXK) and sucrose-non-fermenting 1 (Snf1)-related protein kinase 1 (SnRK1) sugar sensors and trehalose pathway genes. The expression of key target genes of HXK and SnRK1 were affected by LL and sugar depletion, while surprisingly HL and strong sugar accumulation only slightly repressed the SnRK1 signalling pathway. In conclusion, we demonstrate that LL profoundly impacted photosynthesis and the transcriptome of S. viridis source leaves, while HL altered sugar levels more than LL. We also present the first evidence that sugar signalling pathways in C4 source leaves may respond to light intensity and sugar accumulation differently from C3 source leaves. [ABSTRACT FROM AUTHOR]

Setaria viridis (L.) Beauv., or green foxtail, is native to Eurasia and is the putative ancestor of foxtail millet. Due to the advantageous genetic characteristics of S. viridis, it is a model species for C4 plants. However, S. viridis has seriously spread to the agricultural system around the world because of its wide adaptability. This study is aimed to understand the distribution of S. viridis in Taiwan, and also to investigate the genetic diversity and relationships among different wild populations. A total of 141 S. viridis collected at 10 sites with sampling sizes ranging from 8 to 24 plants in Taiwan were analyzed by 13 highly polymorphic SSR markers, and 6.1 alleles per locus were detected in our study. The relationships of collected S. viridis mostly corresponded to its distribution in different parts of Taiwan revealed by PCoA and phylogenetic tree. Similarly, the results for population structure showed the significance of collecting site or geographical factors. Finally, the extent of gene flow was studied with the genetic differentiation (FST) and Nm values, and two S. viridis populations were found to significantly contain the existence of gene-flow events. In conclusion, S. viridis showed a pattern of low diversity and heterozygosity within a population, but high differentiation among populations because of its selfing attribute and the barriers of sea and mountain range for gene flow. In addition, the founder effect may be the other reason for this pattern of population genetic structure.

Key message: The core set of biosynthetic genes potentially involved in developmental lignification was identified in the model C4 grass Setaria viridis. Lignin has been recognized as a major recalcitrant factor negatively affecting the processing of plant biomass into bioproducts. However, the efficient manipulation of lignin deposition in order to generate optimized crops for the biorefinery requires a fundamental knowledge of several aspects of lignin metabolism, including regulation, biosynthesis and polymerization. The current availability of an annotated genome for the model grass Setaria viridis allows the genome-wide characterization of genes involved in the metabolic pathway leading to the production of monolignols, the main building blocks of lignin. Here we performed a comprehensive study of monolignol biosynthetic genes as an initial step into the characterization of lignin metabolism in S. viridis. A total of 56 genes encoding bona fide enzymes catalyzing the consecutive ten steps of the monolignol biosynthetic pathway were identified in the S. viridis genome. A combination of comparative phylogenetic studies, high-throughput expression analysis and quantitative RT-PCR analysis was further employed to identify the family members potentially involved in developmental lignification. Accordingly, 14 genes clustered with genes from closely related species with a known function in lignification and showed an expression pattern that correlates with lignin deposition. These genes were considered the "core lignin toolbox" responsible for the constitutive, developmental lignification in S. viridis. These results provide the basis for further understanding lignin deposition in C4 grasses and will ultimately allow the validation of biotechnological strategies to produce crops with enhanced processing properties. [ABSTRACT FROM AUTHOR]

Rapid metabolite diffusion across the mesophyll (M) and bundle sheath (BS) cell interface in C4 leaves is a key requirement for C4 photosynthesis and occurs via plasmodesmata (PD). Here, we investigated how growth irradiance affects PD density between M and BS cells and between M cells in two C4 species using our PD quantification method, which combines three‐dimensional laser confocal fluorescence microscopy and scanning electron microscopy. The response of leaf anatomy and physiology of NADP‐ME species, Setaria viridis and Zea mays to growth under different irradiances, low light (100 μmol m−2 s−1), and high light (1,000 μmol m−2 s−1), was observed both at seedling and established growth stages. We found that the effect of growth irradiance on C4 leaf PD density depended on plant age and species. The high light treatment resulted in two to four‐fold greater PD density per unit leaf area than at low light, due to greater area of PD clusters and greater PD size in high light plants. These results along with our finding that the effect of light on M‐BS PD density was not tightly linked to photosynthetic capacity suggest a complex mechanism underlying the dynamic response of C4 leaf PD formation to growth irradiance. Using our recently developed method of visualizing plasmodesmata (PD), we found that the response of PD formation in leaves of C4 grasses to growth irradiance is both plant age and species‐dependent and is not tightly linked to photosynthetic capacity. [ABSTRACT FROM AUTHOR]

Despite the many agronomic benefits of conservation tillage, little is known regarding the effects of reduced tillage on the pest complex in sugar beet. We examined the effects of two types of tillage (strip till versus conventional) and different irrigation rates on yield as well as densities of insect pests, weeds, and a soil-borne plant pathogen in sugar beet. Yields were similar between tillage treatments for two of the three years, but were greater for conventional tillage during one year in which a wet spring may have slowed seedling development in strip-tilled plots. The low irrigation treatment exhibited lower yields in one of three years, regardless of tillage treatment. Eggs of beet leafminer flies were more abundant in conventional tillage on three of eight observation dates, but larval densities did not differ by tillage treatment. Bean aphid incidences generally were positively related to irrigation rate. Total weed counts within beet rows did not differ by tillage or irrigation, but between-row counts were greater for the high irrigation treatment during two years. Area under the disease progress curve for Rhizoctonia crown and root rot was higher in conventional tillage during one year. The results presented here show that strip-till sugar beet can be produced with yields comparable to conventional tillage without compromising pest management programs. [ABSTRACT FROM AUTHOR]

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Background: C4 photosynthesis is a key domain of plant research with outcomes ranging from crop quality improvement, biofuel production and efficient use of water and nutrients. A metabolic network model of C4 "lab organism" Setaria viridis with extensive gene-reaction associations can accelerate target identification for desired metabolic manipulations and thereafter in vivo validation. Moreover, metabolic reconstructions have also been shown to be a significant tool to investigate fundamental metabolic traits. Results: A mass and charge balance genome-scale metabolic model of Setaria viridis was constructed, which was tested to be able to produce all major biomass components in phototrophic and heterotrophic conditions. Our model predicted an important role of the utilization of NH 4 + and NO 3 − ratio in balancing charges in plants. A multi-tissue extension of the model representing C4 photosynthesis was able to utilize NADP-ME subtype of C4 carbon fixation for the production of lignocellulosic biomass in stem, providing a tool for identifying gene associations for cellulose, hemi-cellulose and lignin biosynthesis that could be potential target for improved lignocellulosic biomass production. Besides metabolic engineering, our modeling results uncovered a previously unrecognized role of the 3-PGA/triosephosphate shuttle in proton balancing. Conclusions: A mass and charge balance model of Setaria viridis, a model C4 plant, provides the possibility of system-level investigation to identify metabolic characteristics based on stoichiometric constraints. This study demonstrated the use of metabolic modeling in identifying genes associated with the synthesis of particular biomass components, and elucidating new role of previously known metabolic processes. [ABSTRACT FROM AUTHOR]

Abstract High concentrations of vanadium, a ubiquitous element in the environment, in growing media leads to deformation of root structure and leaf chlorosis and necrosis, consequently affecting the translocations of nutrients and essential elements. However, the effects of vanadium on essential element uptake, and the interactions of essential elements in the presence of vanadium, remain incompletely understood. To elucidate the effects of different concentrations of vanadium on major and trace essential elements and plant growth, a native plant species growing in a vanadium mining area, Setaria viridis (dog tail's grass), was incubated in solutions containing 0–55.8 mg/L vanadium. The shoot accumulation of four major essential elements and five trace essential elements was detected, and the root length and stem height were measured. The results showed that vanadium in soil solution enhanced the accumulation of all major essential elements in shoot. Vanadium concentrations lower than 47.4 mg/L showed an obvious positive (p < 0.05) effect on P accumulation and translocation. In the case of trace essential elements, there were threshold values for solution vanadium stimulation of element uptake. The threshold values for Cu and Zn, Fe, and Mo uptake were 4.3, 16.3, and 40.6 mg/L, respectively. When vanadium levels surpassed these values, accumulation was suppressed and the solution vanadium concentrations attenuated the solution-to-shoot translocation of most of the essential elements. Among the trace essential elements, translocation of Fe was obviously enhanced (p < 0.05) by vanadium. Solution vanadium also enhanced plant growth at lower concentrations and inhibited it at higher levels. The threshold values for stem height and root length were 36.8 and 16.3 mg/L, respectively. Concentrations of 40 and 55.8 mg/L vanadium in soil solution caused a 50% decrease in root length and stem height, respectively, showing that root length of Setaria viridis is more susceptible to vanadium toxicity than stem growth. Highlights • V in soil solution enhanced the accumulations of major essential elements in shoots. • V in soil solution obviously increased translocations of P and Fe. • The 40 and 55.8 mg/L V caused 50% decrease in root length and stem height. • V lower than 4.3, 16.3, 40.6 mg/L stimulate the accumulations of Cu and Zn, Fe, Mo. [ABSTRACT FROM AUTHOR]

Herbaspirillum seropedicae is an endophytic bacterium that establishes an association with a variety of plants, such as rice, corn, and sugarcane, and can significantly increase plant growth. H. seropedicae produces polyhydroxybutyrate (PHB), stored in the form of insoluble granules. Little information is available on the possible role of PHB in bacterial root colonization or in plant growth promotion. To investigate whether PHB is important for the association of H. seropedicae with plants, we inoculated H. seropedicae strain SmR1 and mutants defective in PHB production (ΔphaP1, ΔphaP12, ΔphaC1, ΔphaR) or mobilization (ΔphaZ1.2) onto roots of Setaria viridis. The strains producing high amounts of PHB colonized roots, significantly increasing root area and the number of lateral roots compared to PHB negative strains. H. seropedicae grows under microaerobic conditions, which can be found in the rhizosphere. When grown in low oxygen conditions, only the parental strain and ΔphaP2 mutant exhibited normal growth. The lack of normal growth under low oxygen correlated with the inability to stimulate plant growth, although there was no effect on the level of root colonization. The data suggest that PHB is produced in the root rhizosphere and plays a role in maintaining normal metabolism under microaerobic conditions. To confirm this, we screened for GFP expression under the control of the H. seropedicae promoters of the PHA synthase and PHA depolymerase genes in the rhizosphere. PHB synthesis is active on the root surface and later PHB depolymerase expression is activated. [ABSTRACT FROM AUTHOR]

Setaria viridis has recently emerged as an ideal model species to genetically characterize the C4 monocotyledonous grasses via a molecular modification approach. Soil salinization has become a compelling agricultural problem globally with salinity adversely impacting the yield potential of many of the major cereals. Small regulatory molecules of RNA, termed microRNAs (miRNAs), were originally demonstrated crucial for developmental gene expression regulation in plants, however, miRNAs have since been shown to additionally command a central regulatory role in abiotic stress adaptation. Therefore, a small RNA sequencing approach was employed to profile the salt stress responsive miRNA landscapes of the shoot and root tissues of two Setaria viridis accessions (A10 and ME034V) amenable to molecular modification. Small RNA sequencing-identified abundance alterations for miRNAs, miR169, miR395, miR396, miR397, miR398 and miR408, were experimentally validated via RT-qPCR. RT-qPCR was further applied to profile the molecular response of the miR160 and miR167 regulatory modules to salt stress. This analysis revealed accession- and tissue-specific responses for the miR160 and miR167 regulatory modules in A10 and ME034V shoot and root tissues exposed to salt stress. The findings reported here form the first crucial step in the identification of the miRNA regulatory modules to target for molecular manipulation to determine if such modification provides S. viridis with an improved tolerance to salt stress.

Setaria (L.) P. Beauv is a genus of grasses that belongs to the Poaceae (grass) family, subfamily Panicoideae. Two members of the Setaria genus, Setaria italica (foxtail millet) and S. viridis (green foxtail), have been studied extensively over the past few years as model species for C4-photosynthesis and to facilitate genome studies in complex Panicoid bioenergy grasses. We exploited the available genetic and genomic resources for S. italica and its wild progenitor, S. viridis, to study the genetic basis of seed shattering. Reduced shattering is a key trait that underwent positive selection during domestication. Phenotyping of F2:3 and recombinant inbred line (RIL) populations generated from a cross between S. italica accession B100 and S. viridis accession A10 identified the presence of additive main effect quantitative trait loci (QTL) on chromosomes V and IX. As expected, enhanced seed shattering was contributed by the wild S. viridis. Comparative analyses pinpointed Sh1 and qSH1, two shattering genes previously identified in sorghum and rice, as potentially underlying the QTL on Setaria chromosomes IX and V, respectively. The Sh1 allele in S. italica was shown to carry a PIF/Harbinger MITE in exon 2, which gave rise to an alternatively spliced transcript that lacked exon 2. This MITE was universally present in S. italica accessions around the world and absent from the S. viridis germplasm tested, strongly suggesting a single origin of foxtail millet domestication. The qSH1 gene carried two MITEs in the 5′UTR. Presence of one or both MITEs was strongly associated with cultivated germplasm. If the MITE insertion(s) in qSH1 played a role in reducing shattering in S. italica accessions, selection for the variants likely occurred after the domestication of foxtail millet.

Heterotrimeric G-proteins are key regulators of a multitude of growth and development pathways in eukaryotes. Along with the conserved G-protein components found in all organisms, plants have certain novel variants with unique architecture, which may be involved in the regulation of plant-specific traits. The higher plant-specific type III (or Class C) Gγ protein, which possesses a large C terminal extension, represented by AGG3 in Arabidopsis, is one such variant of canonical Gγ proteins. The type III Gγ proteins are involved in regulation of many agronomically important traits in plants, including seed yield, organ size regulation, abscisic acid (ABA)-dependent signaling and stress responses, and nitrogen use efficiency. However, the extant data, especially in the monocots, present a relatively complex and sometimes contradictory picture of the regulatory role of these proteins. It remains unclear if the positive traits observed in certain naturally occurring populations are due to the presence of specific allelic variants of the proteins or due to the altered expression of the gene itself. To address these possibilities, we have overexpressed the Arabidopsis AGG3 gene in the model monocot Setaria viridis and systematically evaluated its role in conferring agriculturally relevant phenotypes. Our data show that AtAGG3 is indeed functional in Setaria and suggest that a subset of the traits affected by the type III Gγ proteins are indeed positively correlated with the gene expression level, while others might have more complex, allele specific regulation.

ABSTRACT Understanding the critical period of weed competition is indispensable in the development of an effective weed management program in field crops. Current experiment was planned to evaluate the critical growth period ofSetaria and level of yield losses associated with delay in weeding in rain-fed drip irrigated wheat production system of Saudi Arabia. Field experiment was conducted to evaluate the effect of weeding interval (07-21, 14-28, 21-35, 28-42 and 35-49 days after sowing) and drought stress (75% and 50% of field capacity) on Setaria growth, wheat yield and water use efficiency. Season long weedy check and wellwatered (100% FC) plots were also maintained for comparison. Weeding interval and drought stress significantly (p ≤ 0.05) affected the growth and yield of Setaria and wheat. Drought stress from 75% to 50% FC resulted in reductions of 29-40% in Setaria height, 14-27% in Setaria density and 11-26% in Setaria dry biomass. All weeding intervals except 35-49 DAS significantly suppressedSetaria growth as compared with control. Delay in weeding increased weed-crop competition interval and reduced wheat yield and yield contributors. Therefore, the lowest yield of 1836 kg ha-1 was attained for weeding interval of 35-49 DAS at 50% FC. Water use efficiency and harvest index increased with decreasing FC levels but reduced with delay in weeding. Correlation analysis predicted negative association ofSetariadensity with wheat yield and yield contributors and the highest negative association was for harvest index (-0.913) and water use efficiency (-0.614). Early management of Setaria is imperative for successful wheat production otherwise yield losses are beyond economical limits.

The vascular plant-specific, cysteine-rich type III Gγ proteins, which are integral components of the heterotrimeric G-protein complex, play crucial roles in regulating a multitude of plant processes, including those related to crop yield and responses to abiotic stresses. The presence of multiple copies of type III Gγ proteins in most plants and a propensity of the presence of specific truncated alleles in many cultivated crops present an ambiguous picture of their roles in modulating specific responses. AGG3 is a canonical type III Gγ protein of Arabidopsis, and its overexpression in additional model crops offers the opportunity to directly evaluate the effects of protein expression levels on plant phenotypes. We have shown that AGG3 overexpression in the monocot model Setaria viridis leads to an increase in seed yield. In this study, we have investigated the response of the S. viridis plants overexpressing AGG3 to heat stress (HS), one of the most important abiotic stresses affecting crops worldwide. We show that a short span of HS at a crucial developmental time point has a significant effect on plant yield in the later stages. We also show that plants with higher levels of AGG3 are more tolerant to HS. This is attributed to an altered regulation of stress-responsive genes and improved modulation of the photosynthetic efficiency during the stress. Overall, our results confirm that AGG3 plays a crucial role in regulating plant responses to unfavorable environmental conditions and may contribute positively to avoiding crop yield losses., (© The Author(s) 2023. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Physical trauma, dietary factors, toxins, immune-mediated disorders, and viral infections are known causes of equine stomatitis. There are also few reports of grass awn-associated stomatitis in horses. Movement of 323 horses was restricted at a Hungarian racetrack because of a suspected vesicular stomatitis (VS) outbreak. Many horses were affected at the same time, and an infectious disease or common offending source was suspected. To establish the nutritional origin of the feed, botanical examination and a food provocation test were carried out. Two healthy adult horses were fed exclusively with the hay of concern for a two-week period. All horses at the racetrack and the experimental horses were clinically examined daily and tested for VS, viral arteritis, glanders, and equine herpesviruses. Biopsy samples were taken from the oral lesions to characterize the histological alterations. Botanical analysis revealed that more than 15% of the forage was foxtail grass (Setaria viridis) . The nutrient content of the forage was adequate for horse maintenance, while its mold and yeast counts were below the reference limits. Competition horses showed signs of depression, decreased appetite, and drooling and ulceration of the lips, tongues, and gingiva after four hours of exposure to the tested forage or hay. The horses in the feeding trial showed the first clinical signs of oral papules on day four, and then showed rupturing pustules, ulcers, and extensive granulation tissues on day seven. Experimental horses did not show signs of depression or loss of appetite. Stomatitis healed spontaneously when the hay was changed. Results of the serological tests, hematological tests, biochemical analysis, and gastroscopy did not show significant alterations. Biopsy samples from both the competition and the experimental horses invariably showed grass awns surrounded by reactive mixed inflammatory cells and granulomatous inflammation. Since differential diagnosis of ulcerative stomatitis include highly contagious viral diseases like VS, quarantine measurements are necessary during stomatitis outbreaks. Differentiation based exclusively on clinical signs is not recommended, although wedged plant particles along the periodontal gingival sulcus might be indicative of inappropriate forage source. Evaluation of the feed in case of a stomatitis outbreak should be immediately performed. In case of grass awn-associated stomatitis, differences are noticed in the severity of lesions possibly based on plant types and plant percentage in the hay. As such, the extent to which foxtail grass-contaminated hay causes ulcerative gingivitis may be increasing because of recent changes in climate. [ABSTRACT FROM AUTHOR]

Setaria (L.) P. Beauv is a genus of grasses that belongs to the Poaceae (grass) family, subfamily Panicoideae. Two members of the Setaria genus, Setaria italica (foxtail millet) and S. viridis (green foxtail), have been studied extensively over the past few years as model species for C4-photosynthesis and to facilitate genome studies in complex Panicoid bioenergy grasses. We exploited the available genetic and genomic resources for S. italica and its wild progenitor, S. viridis, to study the genetic basis of seed shattering. Reduced shattering is a key trait that underwent positive selection during domestication. Phenotyping of F2:3 and recombinant inbred line (RIL) populations generated from a cross between S. italica accession B100 and S. viridis accession A10 identified the presence of additive main effect quantitative trait loci (QTL) on chromosomes V and IX. As expected, enhanced seed shattering was contributed by the wild S. viridis. Comparative analyses pinpointed Sh1 and qSH1, two shattering genes previously identified in sorghum and rice, as potentially underlying the QTL on Setaria chromosomes IX and V, respectively. The Sh1 allele in S. italica was shown to carry a PIF/Harbinger MITE in exon 2, which gave rise to an alternatively spliced transcript that lacked exon 2. This MITE was universally present in S. italica accessions around the world and absent from the S. viridis germplasm tested, strongly suggesting a single origin of foxtail millet domestication. The qSH1 gene carried two MITEs in the 50 UTR. Presence of one or both MITEs was strongly associated with cultivated germplasm. If the MITE insertion(s) in qSH1 played a role in reducing shattering in S. italica accessions, selection for the variants likely occurred after the domestication of foxtail millet. [ABSTRACT FROM AUTHOR]

Background and Aims Setaria viridis is being promoted as a model C4 photosynthetic plant because it has a small genome (~515 Mb), a short life cycle (~60 d) and it can be transformed. Unlike other C4 grasses such as maize, however, there is very little information about how C4 leaf anatomy (Kranz anatomy) develops in S. viridis. As a foundation for future developmental genetic studies, we provide an anatomical and ultrastructural framework of early shoot development in S. viridis, focusing on the initiation of Kranz anatomy in seed leaves. Methods Setaria viridis seeds were germinated and divided into five stages covering development from the dry seed (stage S0) to 36 h after germination (stage S4). Material at each of these stages was examined using conventional light, scanning and transmission electron microscopy. Key Results Dry seeds contained three embryonic leaf primordia at different developmental stages (plastochron 1-3 primordia). The oldest (P3) leaf primordium possessed several procambial centres whereas P2 displayed only ground meristem. At the tip of P3 primordia at stage S4, C4 leaf anatomy typical of the malate dehydrogenasedependent nicotinamide dinucleotide phosphate (NADP-ME) subtype was evident in that vascular bundles lacked a mestome layer and were surrounded by a single layer of bundle sheath cells that contained large, centrifugally located chloroplasts. Two to three mesophyll cells separated adjacent vascular bundles and one mesophyll cell layer on each of the abaxial and adaxial sides delimited vascular bundles from the epidermis. Conclusions The morphological trajectory reported here provides a foundation for studies of gene regulation during early leaf development in S. viridis and a framework for comparative analyses with other C4 grasses. [ABSTRACT FROM AUTHOR]

Mesophyll conductance (gm) limits rates of C3 photosynthesis but little is known about its role in C4 photosynthesis. If gm were to limit C4 photosynthesis, it would likely be at low CO2 concentrations (pCO2). However, data on C4-gm across ranges of pCO2 are scarce. We describe the response of C4-gm to short-term variation in pCO2, at three temperatures in Setaria viridis, and at 25 °C in Zea mays. Additionally, we quantified the effect of finite gm calculations of leakiness (ϕ) and the potential limitations to photosynthesis imposed by stomata, mesophyll, and carbonic anhydrase (CA) across pCO2. In both species, gm increased with decreasing pCO2. Including a finite gm resulted in either no change or increased ϕ compared with values calculated with infinite gm depending on whether the observed 13C discrimination was high (Setaria) or low (Zea). Post-transitional regulation of the maximal PEP carboxylation rate and PEP regeneration limitation could influence estimates of gm and ϕ. At pCO2 below ambient, the photosynthetic rate was limited by CO2 availability. In this case, the limitation imposed by the mesophyll was similar or slightly lower than stomata limitation. At very low pCO2, CA further constrained photosynthesis. High gm could increase CO2 assimilation at low pCO2 and improve photosynthetic efficiency under situations when CO2 is limited, such as drought. [ABSTRACT FROM AUTHOR]

A correction to the article "Temperature Response of Mesophyll Conductance in Three C4 Species Calculated With Two Methods: 18O Discrimination and In Vitro Vpmax" by N. Ubierna and colleagues is presented.

Setaria viridis (green foxtail) is an important model plant for the study of C4 photosynthesis in panicoid grasses, and is fast emerging as a system of choice for the study of plant development, domestication, abiotic stress responses and evolution. Basic research findings in Setaria are expected to advance research not only in this species and its close relative S. italica (foxtail millet), but also in other panicoid grasses, many of which are important food or bioenergy crops. Here we report on the standardization of multiple growth and development assays for S. viridis under controlled conditions, and in response to several phytohormones and abiotic stresses. We optimized these assays at three different stages of the plant’s life: seed germination and post-germination growth using agar plate-based assays, early seedling growth and development using germination pouch-based assays, and adult plant growth and development under environmentally controlled growth chambers and greenhouses. These assays will be useful for the community to perform large scale phenotyping analyses, mutant screens, comparative physiological analysis, and functional characterization of novel genes of Setaria or other related agricultural crops. Precise description of various growth conditions, effective treatment conditions and description of the resultant phenotypes will help expand the use of S. viridis as an effective model system.

Acidic soils are distributed worldwide, predominantly in tropical and subtropical areas, reaching around 50% of the arable soil. This type of soil strongly reduces crop production, mainly because of the presence of aluminum, which has its solubility increased at low pH levels. A well-known physiological mechanism used by plants to cope with Al stress involves activation of membrane transporters responsible for organic acid anions secretion from the root apex to the rhizosphere, which chelate Al, preventing its absorption by roots. In sorghum, a membrane transporter gene belonging to multidrug and toxic compound extrusion (MATE) family was identified and characterized as an aluminum-activated citrate transporter gene responsible for Al tolerance in this crop. Setaria viridis is an emerging model for C4 species and it is an important model to validate some genes for further C4 crops transformation, such as sugarcane, maize, and wheat. In the present work, Setaria viridis was used as a model plant to overexpress a newly identified MATE gene from Brachypodium distachyon (BdMATE), closely related to SbMATE, for aluminum tolerance assays. Transgenic S. viridis plants overexpressing a BdMATE presented an improved Al tolerance phenotype, characterized by sustained root growth and exclusion of aluminum from the root apex in transgenic plants, as confirmed by hematoxylin assay. In addition, transgenic plants showed higher root citrate exudation into the rhizosphere, suggesting that Al tolerance improvement in these plants could be related to the chelation of the metal by the organic acid anion. These results suggest that BdMATE gene can be used to transform C4 crops of economic importance with improved aluminum tolerance.

The fungus Magnaporthiopsis maydis is a soil-borne, seed-borne vascular wilt pathogen that causes severe damage to sensitive Zea mays L. (maize) hybrids throughout Egypt, Israel, India, Spain, and other countries. It can undergo virulence variations and survive as spores, sclerotia, or mycelia on plant residues. Maize, Lupinus termis L. (lupine) and Gossypium hirsutum L. (cotton) are the only known hosts of M. maydis. Identification of new plant hosts that can assist in the survival of the pathogen is an essential step in restricting disease outbreak and spread. Here, by field survey and growth chamber pathogenicity test, accompanied by real-time PCR analysis, the presence of the fungal DNA inside the roots of cotton (Pima cv.) plants was confirmed in infested soil. Moreover, we identified M. maydis in Setaria viridis (green foxtail) and Citrullus lanatus (watermelon, Malali cv.). Infected watermelon sprouts had delayed emergence and development, were shorter, and had reduced root and shoot biomass. M. maydis infection also affected root biomass and phenological development of cotton plants but caused only mild symptoms in green foxtail. No M. maydis DNA was detected in Hordeum vulgare (barley, Noga cv.) and the plants showed no disease symptoms except for reduced shoot weight. These findings are an important step towards uncovering the host range and endophytic behavior of M. maydis, encouraging expanding this evaluation to other plant species.