Genome-wide association study reveals genetic loci for ten trace elements in foxtail millet (Setaria italica).

KEY MESSAGE: One hundred and fifty-five QTL for trace element concentrations in foxtail millet were identified using a genome-wide association study, and a candidate gene associated with Ni-Co-Cr concentrations was detected. Foxtail millet (Setaria italica) is an important regional crop known for its rich mineral nutrient content, which has beneficial effects on human health. We assessed the concentrations of ten trace elements (Ba, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, and Zn) in the grain of 408 foxtail millet accessions. Significant differences in the concentrations of five elements (Ba, Co, Ni, Sr, and Zn) were observed between two subpopulations of spring- and summer-sown foxtail millet varieties. Moreover, 84.4% of the element pairs exhibited significant correlations. To identify the genetic factors influencing trace element accumulation, a comprehensive genome-wide association study was conducted, identifying 155 quantitative trait locus (QTL) for the ten trace elements across three different environments. Among them, ten QTL were consistently detected in multiple environments, including qZn2.1, qZn4.4, qCr4.1, qFe6.3, qFe6.5, qCo6.1, qPb7.3, qPb7.5, qBa9.1, and qNi9.1. Thirteen QTL clusters were detected for multiple elements, which partially explained the correlations between elements. Additionally, the different concentrations of five elements between foxtail millet subpopulations were caused by the different frequencies of high-concentration alleles associated with important marker-trait associations. Haplotype analysis identified a candidate gene SETIT_036676mg associated with Ni accumulation, with the GG haplotype significantly increasing Ni-Co-Cr concentrations in foxtail millet. A cleaved amplified polymorphic sequence marker (cNi6676) based on the two haplotypes of SETIT_036676mg was developed and validated. Results of this study provide valuable reference information for the genetic research and improvement of trace element content in foxtail millet.

Gastroprotective Effect of Isoferulic Acid Derived from Foxtail Millet Bran against Ethanol-Induced Gastric Mucosal Injury by Enhancing GALNT2 Enzyme Activity.

Excessive alcohol consumption has led to the prevalence of gastrointestinal ailments. Alleviating gastric disorders attributed to alcohol-induced thinning of the mucus layer has centered on enhancing mucin secretion as a pivotal approach. In this study, foxtail millet bran polyphenol BPIS was divided into two components with MW < 200 D and MW > 200 D by molecular interception technology. Combined with MTT, cell morphology observation, and trypan blue staining, isoferulic acid (IFA) within the MW < 200 D fraction was determined as the effective constituent to mitigate ethanol-induced damage of gastric epithelial cells. Furthermore, a Wistar rat model with similar clinical features to alcohol-induced gastric mucosal injury was established. Then, gastric morphological observation, H&E staining, and assessments of changes in gastric hexosamine content and gastric wall binding mucus levels were carried out, and the results revealed that IFA (10 mg/Kg) significantly ameliorated alcohol-induced gastric mucosal damage. Finally, we applied techniques including Co-IP, molecular docking, and fluorescence spectroscopy and found that IFA inhibited the alcohol-induced downregulation of N-acetylgalactosamintransferase 2 (GALNT2) activity related to mucus synthesis through direct interaction with GALNT2 in gastric epithelial cells, thus promoting mucin synthesis. Our study lays a foundation for whole grain dietary intervention tailored to individuals suffering from alcoholic gastric mucosal injury.

Understanding the responses of tillering to 2,4-D isooctyl ester in Setaria viridis L.

BACKGROUND: Green foxtail [Setaria viridis (L.)] is one of the most abundant and troublesome annual grass weeds in alfalfa fields in Northeast China. Synthetic auxin herbicide is widely used in agriculture, while how auxin herbicide affects tillering on perennial grass weeds is still unclear. A greenhouse experiment was conducted to examine the effects of auxin herbicide 2,4-D on green foxtail growth, especially on tillers. RESULTS: In the study, 2,4-D isooctyl ester was used. There was an inhibition of plant height and fresh weight on green foxtail after application. The photosynthetic rate of the leaves was dramatically reduced and there was an accumulation of malondialdehyde (MDA) content. Moreover, applying 2,4-D isooctyl ester significantly reduced the tillering buds at rates between 2100 and 8400 ga. i. /ha. Transcriptome results showed that applying 2,4-D isooctyl ester on leaves affected the phytohormone signal transduction pathways in plant tillers. Among them, there were significant effects on auxin, cytokinin, abscisic acid (ABA), gibberellin (GA), and brassinosteroid signaling. Indeed, external ABA and GA on leaves also limited tillering in green foxtail. CONCLUSIONS: These data will be helpful to further understand the responses of green foxtail to 2, 4-D isooctyl ester, which may provide a unique perspective for the development and identification of new target compounds that are effective against this weed species.

Identification, screening and molecular mechanisms of natural stable angiotensin-converting enzyme (ACE) inhibitory peptides from foxtail millet protein hydrolysates: a combined in silico and in vitro study.

The stability of bioactive peptides under various food processing conditions is the basis for their use in industrial manufacturing. This study aimed to identify natural ACE inhibitors with excellent stability and investigate their physicochemical properties and putative molecular mechanisms. Five novel ACE inhibitory peptides (QDPLFPL, FPGVSPF, SPAQLLPF, LVPYRP, and WYWPQ) were isolated and identified using RP-HPLC and Nano LC-MS/MS with foxtail millet protein hydrolysates as the raw material. These peptides are non-toxic and exhibit strong ACE inhibitory activity in vitro (IC50 values between 0.13 mg mL-1 and 0.56 mg mL-1). In addition to QDPLFPL, FPGVSPF, SPAQLLPF, LVPYRP, and WYWPQ have excellent human intestinal absorption. Compared to FPGVSPF and SPAQLLPF, the stable helical structure of LVPYRP and WYWPQ allows them to maintain high stability under conditions that mimic gastrointestinal digestion and various food processing (temperatures, pH, sucrose, NaCl, citric acid, sodium benzoate, Cu2+, Zn2+, K+, Mg2+, Ca2+). The results of molecular docking and molecular dynamics simulation suggest that LVPYRP has greater stability and binding capacity to ACE than WYWPQ. LVPYRP might attach to the active pockets (S1, S2, and S1') of ACE via hydrogen bonds and hydrophobic interactions, then compete with Zn2+ in ACE to demonstrate its ACE inhibitory activity. The binding of LVPYRP to ACE enhances the rearrangement of ACE's active structural domains, with electrostatic and polar solvation energy contributing the most energy to the binding. Our findings suggested that LVPYRP derived from foxtail millet protein hydrolysates has the potential to be incorporated into functional foods to provide antihypertensive benefits.

Effects of copper, and aluminium in ionic, and nanoparticulate form on growth rate and gene expression of Setaria italica seedlings.

This study aims to determine the effects of copper, copper oxide nanoparticles, aluminium, and aluminium oxide nanoparticles on the growth rate and expression of ACT-1, CDPK, LIP, NFC, P5CR, P5CS, GR, and SiZIP1 genes in five days old seedling of Setaria italica ssp. maxima, cultivated in hydroponic culture. Depending on their concentration (ranging from 0.1 to 1.8 mg L-1), all tested substances had both stimulating and inhibiting effects on the growth rate of the seedlings. Copper and copper oxide-NPs had generally a stimulating effect whereas aluminium and aluminium oxide-NPs at first had a positive effect but in higher concentrations they inhibited the growth. Treating the seedlings with 0.4 mg L-1 of each tested toxicant was mostly stimulating to the expression of the genes and reduced the differences between the transcript levels of the coleoptiles and roots. Increasing concentrations of the tested substances had both stimulating and inhibiting effects on the expression levels of the genes. The highest expression levels were usually noted at concentrations between 0.4 and 1.0 mg/L of each metal and metal nanoparticle, except for SiZIP1, which had the highest transcript amount at 1.6 mg L-1 of Cu2+ and at 0.1-0.8 mg L-1 of CuO-NPs, and LIP and GR from the seedling treated with Al2O3-NPs at concentrations of 0.1 and 1.6 mg L-1, respectively.

The importance of starch chain-length distribution for in vitro digestion of ungelatinized and retrograded foxtail millet starch.

The digestibility of ungelatinized, short-term retrograded and long-term retrograded starch from foxtail millet was investigated and correlated with starch chain length distributions (CLDs). Some variations in starch CLDs of different varieties were obtained. Huangjingu and Zhonggu 9 had higher average chain lengths of debranched starch and lower average chain length ratios of amylopectin and amylose than Dajinmiao and Jigu 168. Compared to ungelatinized starch, retrogradation significantly increased the estimated glycemic index (eGI), whereas significantly decreased the resistant starch (RS). In contrast, long-term retrograded starches have lower eGI (93.33-97.37) and higher RS (8.04-14.55%) than short-term retrograded starch. PCA and correlation analysis showed that amylopectin with higher amounts of long chains and longer long chains contributed to reduced digestibility in ungelatinized starch. Both amylose and amylopectin CLDs were important for the digestibility of retrograded starch. This study helps a better understanding of the interaction of starch CLDs and digestibility during retrogradation.

QTL mapping of downy mildew resistance in foxtail millet by SLAF­seq and BSR-seq analysis.

KEY MESSAGE: Key message Three major QTLs for resistance to downy mildew were located within an 0.78 Mb interval on chromosome 8 in foxtail millet. Downy mildew, a disease caused by Sclerospora graminicola, is a serious problem that jeopardizes the yield and quality of foxtail millet. Breeding resistant varieties represents one of the most economical and effective solutions, yet there is a lack of molecular markers related to the resistance. Here, a mapping population comprising of 158 F6:7 recombinant inbred lines (RILs) was constructed from the crossing of G1 and JG21. Based on the specific locus amplified fragment sequencing results, a high-density linkage map of foxtail millet with 1031 bin markers, spanning 1041.66 cM was constructed. Based on the high-density linkage map and the phenotype data in four environments, a total of nine quantitative trait loci (QTL) associated with resistance to downy mildew were identified. Further BSR-seq confirmed the genomic regions containing the potential candidate genes related to downy mildew resistance. Interestingly, a 0.78-Mb interval between C8M257 and C8M268 on chromosome 8 was highlighted because of its presence in three major QTL, qDM8_1, qDM8_2, and qDM8_4, which contains 10 NBS-LRR genes. Haplotype analysis in RILs and natural population suggest that 9 SNP loci on Seita8G.199800, Seita8G.195900, Seita8G.198300, and Seita.8G199300 genes were significantly correlated with disease resistance. Furthermore, we found that those genes were taxon-specific by collinearity analysis of pearl millet and foxtail millet genomes. The identification of these new resistance QTL and the prediction of resistance genes against downy mildew will be useful in breeding for resistant varieties and the study of genetic mechanisms of downy mildew disease resistance in foxtail millet.

Genome-wide identification of the MED25 BINDING RING-H2 PROTEIN gene family in foxtail millet (Setaria italica L.) and the role of SiMBR2 in resistance to abiotic stress in Arabidopsis.

MAIN CONCLUSION: The SiMBR genes in foxtail millet were identified and studied. Heterologous expression of SiMBR2 in Arabidopsis can improve plant tolerance to drought stress by decreasing the level of reactive oxygen species. Foxtail millet (Setaria italica L.), a C4 crop recognized for its exceptional resistance to drought stress, presents an opportunity to improve the genetic resilience of other crops by examining its unique stress response genes and understanding the underlying molecular mechanisms of drought tolerance. In our previous study, we identified several genes linked to drought stress by transcriptome analysis, including SiMBR2 (Seita.7G226600), a member of the MED25 BINDING RING-H2 PROTEIN (MBR) gene family, which is related to protein ubiquitination. Here, we have identified ten SiMBR genes in foxtail millet and conducted analyses of their structural characteristics, chromosomal locations, cis-acting regulatory elements within their promoters, and predicted transcription patterns specific to various tissues or developmental stages using bioinformatic approaches. Further investigation of the stress response of SiMBR2 revealed that its transcription is induced by treatments with salicylic acid and gibberellic acid, as well as by salt and osmotic stresses, while exposure to high or low temperatures led to a decrease in its transcription levels. Heterologous expression of SiMBR2 in Arabidopsis thaliana enhanced the plant's tolerance to water deficit by reducing the accumulation of reactive oxygen species under drought stress. In summary, this study provides support for exploring the molecular mechanisms associated with drought resistance of SiMBR genes in foxtail millet and contributing to genetic improvement and molecular breeding in other crops.

Assembly and comparative analysis of the first complete mitochondrial genome of Setaria italica.

MAIN CONCLUSION: In this study, we assembled the first complete mitochondrial genome of Setaria italica and confirmed the multi-branched architecture. The foxtail millet (Setaria italica) holds significant agricultural importance, particularly in arid and semi-arid regions. It plays a pivotal role in diversifying dietary patterns and shaping planting strategies. Although the chloroplast genome of S. italica has been elucidated in recent studies, the complete mitochondrial genome remains largely unexplored. In this study, we employed PacBio HiFi sequencing platforms to sequence and assemble the complete mitochondrial genome. The mitochondrial genome spans a total length of 446,614 base pairs and harbors a comprehensive set of genetic elements, including 33 unique protein-coding genes (PCGs), encompassing 24 unique mitochondrial core genes and 9 variable genes, along with 20 transfer RNA (tRNA) genes and 3 ribosomal RNA (rRNA) genes. Our analysis of mitochondrial PCGs revealed a pronounced codon usage preference. For instance, the termination codon exhibits a marked preference for UAA, while alanine (Ala) exhibits a preference for GCU, and glutamine (Gln) favors CAA. Notably, the maximum Relative Synonymous Codon Usage (RSCU) values for cysteine (Cys) and phenylalanine (Phe) are both below 1.2, indicating a lack of strong codon usage preference for these amino acids. Phylogenetic analyses consistently place S. italica in close evolutionary proximity to Chrysopogon zizanioides, relative to other Panicoideae plants. Collinearity analysis showed that a total of 39 fragments were identified to display homology with both the mitochondrial and chloroplast genomes. A total of 417 potential RNA-editing sites were discovered across the 33 mitochondrial PCGs. Notably, all these editing events involved the conversion of cytosine (C) to uracil (U). Through the employment of PCR validation coupled with Sanger sequencing for the anticipated editing sites of these codons, RNA-editing events were conclusively identified at two specific loci: nad4L-2 and atp6-1030. The results of this study provide a pivotal foundation for advanced genomic breeding research in foxtail millet. Furthermore, they impart essential insights that will be instrumental for forthcoming investigations into the evolutionary and molecular dynamics of Panicoideae species.

High Overexpression of SiAAP9 Leads to Growth Inhibition and Protein Ectopic Localization in Transgenic Arabidopsis.

Amino acid permeases (AAPs) transporters are crucial for the long-distance transport of amino acids in plants, from source to sink. While Arabidopsis and rice have been extensively studied, research on foxtail millet is limited. This study identified two transcripts of SiAAP9, both of which were induced by NO3- and showed similar expression patterns. The overexpression of SiAAP9L and SiAAP9S in Arabidopsis inhibited plant growth and seed size, although SiAAP9 was found to transport more amino acids into seeds. Furthermore, SiAAP9-OX transgenic Arabidopsis showed increased tolerance to high concentrations of glutamate (Glu) and histidine (His). The high overexpression level of SiAAP9 suggested its protein was not only located on the plasma membrane but potentially on other organelles, as well. Interestingly, sequence deletion reduced SiAAP9's sensitivity to Brefeldin A (BFA), and SiAAP9 had ectopic localization on the endoplasmic reticulum (ER). Protoplast amino acid uptake experiments indicated that SiAAP9 enhanced Glu transport into foxtail millet cells. Overall, the two transcripts of SiAAP9 have similar functions, but SiAAP9L shows a higher colocalization with BFA compartments compared to SiAAP9S. Our research identifies a potential candidate gene for enhancing the nutritional quality of foxtail millet through breeding.

Genome-wide identification and functional analysis of the SiCIN gene family in foxtail millet (Setaria italica L.).

Cell wall invertase (CIN) is a vital member of plant invertase (INV) and plays a key role in the breakdown of sucrose. This enzyme facilitates the hydrolysis of sucrose into glucose and fructose, which is crucial for various aspects of plant growth and development. However, the function of CIN genes in foxtail millet (Setaria italica) is less studied. In this research, we used the blast-p of NCBI and TBtools for bidirectional comparison, and a total of 13 CIN genes (named SiCINs) were identified from foxtail millet by using Arabidopsis and rice CIN sequences as reference sequences. The phylogenetic tree analysis revealed that the CIN genes can be categorized into three subfamilies: group 1, group 2, and group 3. Furthermore, upon conducting chromosomal localization analysis, it was observed that the 13 SiCINs were distributed unevenly across five chromosomes. Cis-acting elements of SiCIN genes can be classified into three categories: plant growth and development, stress response, and hormone response. The largest number of cis-acting elements were those related to light response (G-box) and the cis-acting elements related to seed-specific regulation (RY-element). qRT-PCR analysis further confirmed that the expression of SiCIN7 and SiCIN8 in the grain was higher than that in any other tissues. The overexpression of SiCIN7 in Arabidopsis improved the grain size and thousand-grain weight, suggesting that SiCIN7 could positively regulate grain development. Our findings will help to further understand the grain-filling mechanism of SiCIN and elucidate the biological mechanism underlying the grain development of SiCIN.

Characterization of the active components and bioaccessibility of phenolics in differently colored foxtail millets.

Differently colored foxtail millet (Setaria italica) cultivars were compared regarding their amylose, B-complex vitamin, vitamin E, and phenolic compositions, as well as the bioaccessibility of their phenolics in simulated in vitro digestion. Dark-colored foxtail millets contained more thiamine, pyridoxine, and tocopherols, but less riboflavin, than light-colored ones. Phenolics were more abundant in dark-colored cultivars. Insoluble bound fractions accounted for 75%-83% of the total phenolics, with ferulic acid detected as the most plentiful compound. The major bioaccessible phenolic was free ferulic acid, with 100%-120% bioaccessibility, depending on cultivar, followed by p-coumaric acid and isoferulic acid (50%-80%). These relatively high bioaccessibilities were likely due to the release of soluble conjugated or insoluble bound phenolics during digestion. However, the contents of other free phenolics were largely decreased following in vitro digestion, resulting in low bioaccessibility, which also means that the release from the conjugated and bound fractions was poor.

Inhibitory Effects of Soluble Dietary Fiber from Foxtail Millet on Colorectal Cancer by the Restoration of Gut Microbiota.

Colorectal cancer (CRC) is a common malignant tumor that occurs in the colon. Gut microbiota is a complex ecosystem that plays an important role in the pathogenesis of CRC. Our previous studies showed that the soluble dietary fiber of foxtail millet (FMB-SDF) exhibited significant antitumor activity in vitro. The present study evaluated the anticancer potential of FMB-SDF in the azoxymethane (AOM)- and dextran sodium sulfate (DSS)-induced mouse CRC models. The results showed that FMB-SDF could significantly alleviate colon cancer symptoms in mice. Further, we found that FMB-SDF consumption significantly altered gut microbiota diversity and the overall structure and regulated the abundance of some microorganisms in CRC mice. Meanwhile, KEGG pathway enrichment showed that FMB-SDF can also alleviate the occurrence of colon cancer in mice by regulating certain cancer-related signaling pathways. In conclusion, our findings may provide a novel approach for the prevention and biotherapy of CRC.

Insights into the starch and proteins molecular structure changes of foxtail millet sourdough: Effect of fermentation from grains of cereal to pre-meal.

This study investigated the effects of foxtail millet sourdough fermentation time (0, 8, 16, and 24 h) on the protein structural properties, thermomechanical, fermentation, dynamic rheological, starch granules crystalline regions molecular mobility, and starch microstructural characteristics. The fermentation led to a significant increase in the concentration of free amino acids from protein hydrolysis. Fourier transform infrared spectroscopy (FTIR) revealed changes in protein secondary structure and the presence of functional groups of different bioactive compounds. The result of thermomechanical properties showed a significant increase in the stability (0.70-0.79 min) and anti-retrogradation ability (2.29-3.14 Nm) of lactic acid bacteria (LAB) sourdough compared to the control dough, showing a wider processing applicability with radar profiler index. In contrast, sourdoughs with lower tan δ values had higher elasticity and strength. Scanning electron microscopy showed that the surface of the starch appeared from smooth to uneven with patchy shapes and cavities, which declined the crystallinity from 34.00 % to 21.57 %, 23.64 %, 25.09 %, and 26.34 % respectively. Fermentation changed the To, Tp, Tc, and ΔH of the starch. The results of the study will have great potential for application in the whole grain sourdough industry.

Latitudinal adaptation and dispersal pathway of foxtail millet suggested by geographical distribution of transposable elements inserted in the SiPRR37 gene.

We investigated the variation and geographical distribution of the Pseudo-regulator response 37 (Setaria italica PRR37; SiPRR37) gene, which is involved in heading time (photoperiodism) in foxtail millet. An allele of the SiPRR37 gene, in which an approximately 4.9-kb transposable element (designated TE1) is inserted (a loss-of-function or reduction-of-function type), is distributed sporadically in East Asia and broadly in Southeast Asia and South Asia, implying that this gene is important in latitudinal adaptation. In addition, we found a new allele of SiPRR37 with an insertion of a 360-bp TE (TE2) at this locus and investigated the geographical distribution of this new type. This SiPRR37 allele with TE2 is distributed in Japan, Korea, Nepal, Iran and Turkey. Both TE1 and TE2 are useful markers for tracing foxtail millet dispersal pathways in Asia.

Alternative Splicing Plays a Crucial Role in the Salt Tolerance of Foxtail Millet.

Foxtail millet is an important cereal crop that is relatively sensitive to salt stress, with its yield significantly affected by such stress. Alternative splicing (AS) widely affects plant growth, development, and adaptability to stressful environments. Through RNA-seq analysis of foxtail millet under different salt treatment periods, 2078 AS events were identified, and analyses were conducted on differential gene (DEG), differential alternative splicing gene (DASG), and overlapping gene. To investigate the regulatory mechanism of AS in response to salt stress in foxtail millet, the foxtail millet AS genes SiCYP19, with two AS variants (SiCYP19-a and SiCYP19-b), were identified and cloned. Yeast overexpression experiments indicated that SiCYP19 may be linked to the response to salt stress. Subsequently, we conducted overexpression experiments of both alternative splicing variants in foxtail millet roots to validate them experimentally. The results showed that, under salt stress, both SiCYP19-a and SiCYP19-b jointly regulated the salt tolerance of foxtail millet. Specifically, overexpression of SiCYP19-b significantly increased the proline content and reduced the accumulation of reactive oxygen species (ROS) in foxtail millet, compared to that in SiCYP19-a. This shows that SiCYP19-b plays an important role in increasing the content of proline and promoting the clearance of ROS, thus improving the salt tolerance of foxtail millet.

Identification and Expression Analysis of the WOX Transcription Factor Family in Foxtail Millet (Setaria italica L.).

WUSCHEL-related homeobox (WOX) transcription factors are unique to plants and play pivotal roles in plant development and stress responses. In this investigation, we acquired protein sequences of foxtail millet WOX gene family members through homologous sequence alignment and a hidden Markov model (HMM) search. Utilizing conserved domain prediction, we identified 13 foxtail millet WOX genes, which were classified into ancient, intermediate, and modern clades. Multiple sequence alignment results revealed that all WOX proteins possess a homeodomain (HD). The SiWOX genes, clustered together in the phylogenetic tree, exhibited analogous protein spatial structures, gene structures, and conserved motifs. The foxtail millet WOX genes are distributed across 7 chromosomes, featuring 3 pairs of tandem repeats: SiWOX1 and SiWOX13, SiWOX4 and SiWOX5, and SiWOX11 and SiWOX12. Collinearity analysis demonstrated that WOX genes in foxtail millet exhibit the highest collinearity with green foxtail, followed by maize. The SiWOX genes primarily harbor two categories of cis-acting regulatory elements: Stress response and plant hormone response. Notably, prominent hormones triggering responses include methyl jasmonate, abscisic acid, gibberellin, auxin, and salicylic acid. Analysis of SiWOX expression patterns and hormone responses unveiled potential functional diversity among different SiWOX genes in foxtail millet. These findings lay a solid foundation for further elucidating the functions and evolution of SiWOX genes.

Sugar sensing in C4 source leaves: a gap that needs to be filled.

Plant growth depends on sugar production and export by photosynthesizing source leaves and sugar allocation and import by sink tissues (grains, roots, stems, and young leaves). Photosynthesis and sink demand are tightly coordinated through metabolic (substrate, allosteric) feedback and signalling (sugar, hormones) mechanisms. Sugar signalling integrates sugar production with plant development and environmental cues. In C3 plants (e.g. wheat and rice), it is well documented that sugar accumulation in source leaves, due to source-sink imbalance, negatively feeds back on photosynthesis and plant productivity. However, we have a limited understanding about the molecular mechanisms underlying those feedback regulations, especially in C4 plants (e.g. maize, sorghum, and sugarcane). Recent work with the C4 model plant Setaria viridis suggested that C4 leaves have different sugar sensing thresholds and behaviours relative to C3 counterparts. Addressing this research priority is critical because improving crop yield requires a better understanding of how plants coordinate source activity with sink demand. Here we review the literature, present a model of action for sugar sensing in C4 source leaves, and suggest ways forward.

Reactive oxygen species (ROS) modulate nitrogen signaling using temporal transcriptome analysis in foxtail millet.

Reactive oxygen species (ROS) is a chemically reactive chemical substance containing oxygen and a natural by-product of normal oxygen metabolism. Excessive ROS affect the growth process of crops, which will lead to the decrease of yield. Nitrogen, as a critical nutrient element in plants and plays a vital role in plant growth and crop production. Nitrate is the primary nitrogen source available to plants in agricultural soil and various natural environments. However, the molecular mechanism of ROS-nitrate crosstalk is still unclear. In this study, we used the foxtail millet (Setaria italica L.) as the material to figure it out. Here, we show that excessive NaCl inhibits nitrate-promoted plant growth and nitrogen use efficiency (NUE). NaCl induces ROS accumulation in roots, and ROS inhibits nitrate-induced gene expression in a short time. Surprisingly, low concentration ROS slight promotes and high concentration of ROS inhibits foxtail millet growth under long-term H2O2 treatment. These results may open a new perspective for further exploration of ROS-nitrate signaling pathway in plants.

Systematic Analysis of DNA Demethylase Gene Families in Foxtail Millet (Setaria italica L.) and Their Expression Variations after Abiotic Stresses.

DNA methylation is a highly conserved epigenetic modification involved in many biological processes, including growth and development, stress response, and secondary metabolism. DNA demethylase (DNA-deMTase) genes have been identified in some plant species; however, there are no reports on the identification and analysis of DNA-deMTase genes in Foxtail millet (Setaria italica L.). In this study, seven DNA-deMTases were identified in S. italica. These DNA-deMTase genes were divided into four subfamilies (DML5, DML4, DML3, and ROS1) by phylogenetic and gene structure analysis. Further analysis shows that the physical and chemical properties of these DNA-deMTases proteins are similar, contain the typical conserved domains of ENCO3c and are located in the nucleus. Furthermore, multiple cis-acting elements were observed in DNA-deMTases, including light responsiveness, phytohormone responsiveness, stress responsiveness, and elements related to plant growth and development. The DNA-deMTase genes are expressed in all tissues detected with certain tissue specificity. Then, we investigated the abundance of DNA-deMTase transcripts under abiotic stresses (cold, drought, salt, ABA, and MeJA). The results showed that different genes of DNA-deMTases were involved in the regulation of different abiotic stresses. In total, our findings will provide a basis for the roles of DNA-deMTase in response to abiotic stress.