Abstract
Foxtail millet (Setaria italica) is an important crop species and an emerging model plant for C4 grasses. However, functional genomics research on foxtail millet is challenging because of its long generation time, relatively large stature and recalcitrance to genetic transformation. Here we report the development of xiaomi, a rapid-cycling mini foxtail millet mutant as a C4 model system. Five to six generations of xiaomi can be grown in a year in growth chambers due to its short life cycle and small plant size, similar to Arabidopsis. A point mutation in the Phytochrome C (PHYC) gene was found to be causal for these characteristics. PHYC encodes a light receptor essential for photoperiodic flowering. A reference-grade xiaomi genome comprising 429.94 Mb of sequence was assembled and a gene-expression atlas from 11 different tissues was developed. These resources, together with an established highly efficient transformation system and a multi-omics database, make xiaomi an ideal model system for functional studies of C4 plants.
This is a preview of subscription content, access via your institution
Access options
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
$29.99 / 30 days
cancel any time
Subscribe to this journal
Receive 12 digital issues and online access to articles
$119.00 per year
only $9.92 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
Data availability
The genome assembly, annotation and expression data can be easily accessed at our Multi-omics Database for S. italica (MDSi) (http://sky.sxau.edu.cn/MDSi.htm). The genome assembly and annotation of xiaomi are also available at Genome Warehouse in the Beijing Institute of Genomics Data Center (https://bigd.big.ac.cn/) under accession number GWHAAZD00000000. The raw sequence data have been deposited in the Beijing Institute of Genomics Data Center with the following accession numbers: CRA001973 (Genome sequencing of xiaomi by PacBio), CRA001968 (Hi-C of xiaomi), CRA001972 (isoform sequencing of xiaomi), CRA001967 (Genome resequencing of xiaomi and Jingu21), CRA001953 (RNA-seq of 11 xiaomi tissues), CRA001954 (RNA-seq of the top second leaf of 30-day-old Jingu21), CRA001974 (non-coding RNAs), CRA002603 (genome resequencing of xiaomi-2) and CRA002604 (genome resequencing of 13 transgenic lines). The Yugu1 genome was downloaded from public database Phytozome (https://phytozome.jgi.doe.gov/pz/portal.html). The Zhanggu genome was downloaded from ftp://ftp.genomics.org.cn/pub/Foxtail_millet. Other data can be obtained from the public databases nr (https://ftp.ncbi.nlm.nih.gov/blast/db/FASTA/), KOG (ftp://ftp.ncbi.nih.gov/pub/COG/KOG/), KEGG (https://www.kegg.jp/), TrEMBL (https://www.ebi.ac.uk/uniprot), GO (http://geneontology.org/) and BUSCO embryophyta_odb9 dataset (http://busco.ezlab.org/datasets/embryophyta_odb9.tar.gz). All data and materials are available from the corresponding author upon request. Source data are provided with this paper.
References
Provart, N. J. et al. 50 years of Arabidopsis research: highlights and future directions. N. Phytol. 209, 921–944 (2016).
Brutnell, T. P., Bennetzen, J. L. & Vogel, J. P. Brachypodium distachyon and Setaria viridis: model genetic systems for the grasses. Annu. Rev. Plant Biol. 66, 465–485 (2015).
Doust, A. N., Kellogg, E. A., Devos, K. M. & Bennetzen, J. L. Foxtail millet: a sequence-driven grass model system. Plant Physiol. 149, 137–141 (2009).
Jia, G. et al. A haplotype map of genomic variations and genome-wide association studies of agronomic traits in foxtail millet (Setaria italica). Nat. Genet. 45, 957–961 (2013).
Bennetzen, J. L. et al. Reference genome sequence of the model plant Setaria. Nat. Biotechnol. 30, 555–561 (2012).
Brutnell, T. P. et al. Setaria viridis: a model for C4 photosynthesis. Plant Cell 22, 2537–2544 (2010).
Acharya, B. R. et al. Optimization of phenotyping assays for the model monocot Setaria viridis. Front. Plant Sci. 8, 2172 (2017).
Zhang, G. et al. Genome sequence of foxtail millet (Setaria italica) provides insights into grass evolution and biofuel potential. Nat. Biotechnol. 30, 549 (2012).
Tsai, K. J. et al. Assembling the Setaria italica L. Beauv. genome into nine chromosomes and insights into regions affecting growth and drought tolerance. Sci. Rep. 6, 35076 (2016).
Diao, X., Schnable, J., Bennetzen, J. L. & Li, J. Initiation of Setaria as a model plant. Front. Agr. Sci. Eng. 1, 16–20 (2014).
Lata, C., Gupta, S. & Prasad, M. Foxtail millet: a model crop for genetic and genomic studies in bioenergy grasses. Crit. Rev. Biotechnol. 33, 328–343 (2013).
Li, P. & Brutnell, T. P. Setaria viridis and Setaria italica, model genetic systems for the Panicoid grasses. J. Exp. Bot. 62, 3031–3037 (2011).
Rockwell, N. C., Su, Y. S. & Lagarias, J. C. Phytochrome structure and signaling mechanisms. Annu. Rev. Plant Biol. 57, 837–858 (2006).
Hiei, Y. & Komari, T. Agrobacterium-mediated transformation of rice using immature embryos or calli induced from mature seed. Nat. Protoc. 3, 824–834 (2008).
Sage, R. F. The evolution of C4 photosynthesis. N. Phytol. 161, 341–370 (2004).
Ermakova, M., Danila, F. R., Furbank, R. T. & von Caemmerer, S. On the road to C4 rice: advances and perspectives. Plant J. 101, 940–950 (2020).
Yang, J. et al. Brassinosteroids modulate meristem fate and differentiation of unique inflorescence morphology in Setaria viridis. Plant Cell 30, 48–66 (2018).
Huang, P. et al. Sparse panicle1 is required for inflorescence development in Setaria viridis and maize. Nat. Plants 3, 17054 (2017).
Saha, P. & Blumwald, E. Spike-dip transformation of Setaria viridis. Plant J. 86, 89–101 (2016).
Huang, P. et al. Population genetics of Setaria viridis, a new model system. Mol. Ecol. 23, 4912–4925 (2014).
Hu, S. et al. Xiaowei, a new rice germplasm for large-scale indoor research. Mol. Plant 11, 1418–1420 (2018).
Meissner, R. et al. A new model system for tomato genetics. Plant J. 12, 1465–1472 (1997).
Monte, E. et al. Isolation and characterization of phyC mutants in Arabidopsis reveals complex crosstalk between phytochrome signaling pathways. Plant Cell 15, 1962–1980 (2003).
Takano, M. et al. Distinct and cooperative functions of phytochromes A, B, and C in the control of deetiolation and flowering in rice. Plant Cell 17, 3311–3325 (2005).
Martins, P. K. et al. Setaria viridis floral-dip: a simple and rapid Agrobacterium-mediated transformation method. Biotechnol. Rep. 6, 61–63 (2015).
Liu, Y., Yu, J., Zhao, Q., Zhu, D. & Ao, G. Genetic transformation of millet (Setaria italica) by Agrobacterium-mediated. J. Agric. Biotechnol. 13, 32–37 (2005).
Liu, Y., Yu, J., Ao, G. & Zhao, Q. Factors influencing Agrobacterium-mediated transformation of foxtail millet (Setaria italica). Chin. J. Biochem. Mol. Biol. 23, 531–536 (2007).
Allen, G. C., Flores-Vergara, M. A., Krasynanski, S., Kumar, S. & Thompson, W. F. A modified protocol for rapid DNA isolation from plant tissues using cetyltrimethylammonium bromide. Nat. Protoc. 1, 2320–2325 (2006).
Chakraborty, M., Baldwin-Brown, J. G., Long, A. D. & Emerson, J. J. Contiguous and accurate de novo assembly of metazoan genomes with modest long read coverage. Nucleic Acids Res. 44, e147 (2016).
Koren, S. et al. Canu: scalable and accurate long-read assembly via adaptive k-mer weighting and repeat separation. Genome Res. 27, 722–736 (2017).
Chin, C. S. et al. Phased diploid genome assembly with single-molecule real-time sequencing. Nat. Methods 13, 1050–1054 (2016).
Burton, J. N. et al. Chromosome-scale scaffolding of de novo genome assemblies based on chromatin interactions. Nat. Biotechnol. 31, 1119–1125 (2013).
Li, H. & Durbin, R. Fast and accurate short read alignment with Burrows–Wheeler transform. Bioinformatics 25, 1754–1760 (2009).
Xu, Z. & Wang, H. LTR_FINDER: an efficient tool for the prediction of full-length LTR retrotransposons. Nucleic Acids Res. 35, W265–W268 (2007).
Han, Y. & Wessler, S. R. MITE-Hunter: a program for discovering miniature inverted-repeat transposable elements from genomic sequences. Nucleic Acids Res. 38, e199 (2010).
Price, A. L., Jones, N. C. & Pevzner, P. A. De novo identification of repeat families in large genomes. Bioinformatics 21 (Suppl. 1), i351–i358 (2005).
Edgar, R. C. & Myers, E. W. PILER: identification and classification of genomic repeats. Bioinformatics 21(Suppl 1), i152–i158 (2005).
Wicker, T. et al. A unified classification system for eukaryotic transposable elements. Nat. Rev. Genet. 8, 973–982 (2007).
Bao, W., Kojima, K. K. & Kohany, O. Repbase Update, a database of repetitive elements in eukaryotic genomes. Mob. DNA 6, 11 (2015).
Burge, C. & Karlin, S. Prediction of complete gene structures in human genomic DNA. J. Mol. Biol. 268, 78–94 (1997).
Stanke, M. & Waack, S. Gene prediction with a hidden Markov model and a new intron submodel. Bioinformatics 19(Suppl 2), ii215–ii225 (2003).
Majoros, W. H., Pertea, M. & Salzberg, S. L. TigrScan and GlimmerHMM: two open source ab initio eukaryotic gene-finders. Bioinformatics 20, 2878–2879 (2004).
Blanco, E., Parra, G. & Guigó, R. Using geneid to identify genes. Curr. Protoc. Bioinforma. 18, 4.3.1–4.3.28 (2007).
Korf, I. Gene finding in novel genomes. BMC Bioinf. 5, 59 (2004).
Keilwagen, J. et al. Using intron position conservation for homology-based gene prediction. Nucleic Acids Res. 44, e89 (2016).
Haas, B. J. et al. Improving the Arabidopsis genome annotation using maximal transcript alignment assemblies. Nucleic Acids Res. 31, 5654–5666 (2003).
Dimmer, E. C. et al. The UniProt-GO annotation database in 2011. Nucleic Acids Res. 40, D565–D570 (2012).
Conesa, A. et al. Blast2GO: a universal tool for annotation, visualization and analysis in functional genomics research. Bioinformatics 21, 3674–3676 (2005).
Lowe, T. M. & Eddy, S. R. tRNAscan-SE: a program for improved detection of transfer RNA genes in genomic sequence. Nucleic Acids Res. 25, 955–964 (1997).
Griffiths-Jones, S. et al. Rfam: annotating non-coding RNAs in complete genomes. Nucleic Acids Res. 33, D121–D124 (2005).
Simao, F. A., Waterhouse, R. M., Ioannidis, P., Kriventseva, E. V. & Zdobnov, E. M. BUSCO: assessing genome assembly and annotation completeness with single-copy orthologs. Bioinformatics 31, 3210–3212 (2015).
Bolger, A. M., Lohse, M. & Usadel, B. Trimmomatic: a flexible trimmer for Illumina sequence data. Bioinformatics 30, 2114–2120 (2014).
Kim, D., Langmead, B. & Salzberg, S. L. HISAT: a fast spliced aligner with low memory requirements. Nat. Methods 12, 357–360 (2015).
Li, B., Ruotti, V., Stewart, R. M., Thomson, J. A. & Dewey, C. N. RNA-seq gene expression estimation with read mapping uncertainty. Bioinformatics 26, 493–500 (2010).
Friedlander, M. R., Mackowiak, S. D., Li, N., Chen, W. & Rajewsky, N. miRDeep2 accurately identifies known and hundreds of novel microRNA genes in seven animal clades. Nucleic Acids Res. 40, 37–52 (2012).
Memczak, S. et al. Circular RNAs are a large class of animal RNAs with regulatory potency. Nature 495, 333–338 (2013).
Kurtz, S. et al. Versatile and open software for comparing large genomes. Genome Biol. 5, R12 (2004).
Giordano, F., Stammnitz, M. R., Murchison, E. P. & Ning, Z. scanPAV: a pipeline for extracting presence–absence variations in genome pairs. Bioinformatics 34, 3022–3024 (2018).
Sun, L. et al. TDNAscan: a software to identify complete and truncated T-DNA insertions. Front. Genet. 10, 685 (2019).
Li, W. et al. Gene mapping and functional analysis of the novel leaf color gene SiYGL1 in foxtail millet [Setaria italica (L.) P. Beauv]. Physiol. Plant. 157, 24–37 (2016).
Acknowledgements
We thank D. Grierson, Z. Tian, R. Fray and Y. Jiang for their critical reading of the manuscript, and R. Xia for help in developing the xEGP browser. This work was supported by the National Key R&D Program of China (2018YFD1000700, 2018YFD1000704 and 2018YFD1000702), National Natural Science Foundation of China (31600289, 31471502 and 31371693) and Key R&D Projects of Shanxi Province (201703D211008).
Author information
Authors and Affiliations
Contributions
X.W., Y.H., Z.Y. and Y.S. designed and coordinated the study. Y.H., J.G., S.H. and B.Z. constructed the Jingu21 EMS-mutagenized library and identified the xiaomi mutant. Z.Y., X.W. and H.S. characterized the xiaomi phenotype, cloned the PHYC gene and analysed the sequence data. H.Z., Y.S. and C.W. established the Agrobacterium-mediated genetic transformation system and wrote the relevant part of the manuscript. X.W., Y.H., X.L., Z.Y., J.M., S.M. and M.B. performed downstream analysis of the sequence data. H.S., J.G., S.H. and B.Z. collected the experimental materials. X.W. and J.M. wrote the manuscript. All authors edited and approved the manuscript.
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Peer review information Nature Plants thanks Andrew Doust, Manoj Prasad, Hong Yu and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Extended data
Extended Data Fig. 1 Alternative splicing site of the PHYC gene in xiaomi.
a, RNA-Seq reads of Jingu21. xiaomi genome sequences were used as reference genome. The blue vertical line shows the G-T mutation site. b, RNA-seq reads of xiaomi. The wrong splicing site was marked by a red arrow.
Extended Data Fig. 2 Phenotypic and molecular characterization of the xiaomi-2 mutant.
a, Forty-day-old plants of Jingu21 (wild type, left) and xiaomi-2 (right) plants grown under natural long-day conditions. b, Heading date of Jingu21 and xiaomi-2 under natural field conditions. The heading date of ≥ 20 plants was measured for each replicate (n = 3 biologically independent replicates, ≥ 102 in total). The bottom and top of boxes represent the first and third quartile, respectively. The middle line is the median and the whiskers represent the maximum and minimum values. Statistical analysis was performed using two-tailed Wilcoxon rank-sum test. c, A mature small-sized xiaomi-2 plant (right) compared to Jingu21 (left), at the 68th day in field. d, Plant height of Jingu21 and xiaomi-2 under natural field conditions. The plant height of ≥ 23 plants was measured for each replicate (n = 3 biologically independent replicates, ≥ 83 in total). e, Molecular charicterization of xiaomi-2. Exons and introns are denoted by filled boxes and lines, respectively. P2F and P2R represent a pair of primers used to amplify the fragments harboring the mutation site from the segregating M3 individuals (Primer sequences are listed in Supplementary Table 3). f, Structure of PHYC and its mutation version deduced according to mutations in xiaomi-2. Scale bars, 10 cm in a and c.
Extended Data Fig. 3 Sequence alignment of the GAF domain of PHYC in foxtail millet and its homologs.
Alignment was carried out using Clustal W method of the MegAlign software. Red box indicates the conserved residue Leu across all listed species that is substituted with His in xiaomi-2, demonstrating its functional importance for PHYC. Accession numbers for the aligned sequences: Arabidopsis thaliana NP_198433, Brachypodium distachyon XP_003559446, Brassica napus XP_013680236, Ipomoea nil XP_019162785, Oryza sativa AAF66603, Panicum miliaceum, RLN42126, Solanum lycopersicum NP_001307446, Sorghum bicolor XP_002466441, Triticum aestivum AAU06208, Vitis vinifera ACC6096 and Zea mays XP_008665426. PHYC protein in Jingu21 is presented as for Setaria italica (Si9G09200).
Extended Data Fig. 4 Hi-C interaction matrices show the pairwise correlations between ordered scaffolds along the 9 pseudomolecules.
The intensity of the dark color is proportional to the strength of the correlation.
Extended Data Fig. 5 Transgene segregation in T1 transgenic seeds as visualized for GFP expression.
Dry mature seeds from transgenic lines representing single a, two b, or multiple c, T-DNA insertions were scanned with a dissection microscope equipped with UV light. All experiments were performed for eight independent biological repeats, and similar results were obtained. Scale bars, 2 mm.
Extended Data Fig. 6 PCR confirmation of the site-specific T-DNA insertions identified by genome resequencing.
a and b. An Integrative Genomics Viewer (IGV) display of genome sequencing reads from WT (a) or the transgenic line N2 (b) spanning the T-DNA insertion site 22812363 on chromosome 7. The break point caused by the insertion is marked by an arrow. c. PCR confirmation of the insertion site 33288299 on chromosome 6 in line H2. d. PCR confirmation of the insertion site 22812363 on chromosome 7 in line N2. e. PCR confirmation of the insertion site 39094661 on chromosome 5 in line N8. Note: The genomic DNA for sequencing and PCR was prepared from pooling approximate 50 T1 transgenic seedlings, which explains the heterozygous nature of the T-DNA insertion seen in b-e. M, molecular marker; lane 1, no-transformed xiaomi plants; line 2, transgenic xiaomi plants; line 3, water control; F and R are primers for priming genomic regions flanking LB and RB ends of T-DNA, respectively; both the LB1 and LB2 primers are for T-DNA sequence close to the left border (LB). LB1 is 161 bp further apart from the border than LB2 for the vector pCAMBIA1305GFP, resulting in a band of bigger size in the R/LB1 pair in c. Similarly, LB1 and LB2 are distanced by 183 bp for the p8-GFP vector, thus resulting in different band size between F/LB1 and F/LB2 in d and e. All experiments were performed for three repeats, and similar results were obtained. Primers used are listed in Supplementary Table 3.
Supplementary information
Supplementary Information
Supplementary Figs. 1–7.
Supplementary Tables
Supplementary Tables 1–25.
Supplementary Data 1
SNPs and indels between xiaomi and Yugu1.
Source data
Source Data Fig. 1
Statistical source data.
Source Data Fig. 2
Unprocessed gel.
Source Data Fig. 5
Unprocessed gels.
Source Data Extended Data Fig. 2
Statistical source data.
Source Data Extended Data Fig. 6
Unprocessed gels.
Rights and permissions
About this article
Cite this article
Yang, Z., Zhang, H., Li, X. et al. A mini foxtail millet with an Arabidopsis-like life cycle as a C4 model system. Nat. Plants 6, 1167–1178 (2020). https://doi.org/10.1038/s41477-020-0747-7
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s41477-020-0747-7
This article is cited by
-
Genome-wide identification and expression profiling of the ABI5 gene family in foxtail millet (Setaria italica)
BMC Plant Biology (2024)
-
Chromosome-level genome assembly of the diploid oat species Avena longiglumis
Scientific Data (2024)
-
Genome-wide identification of AAAP gene family and expression analysis in response to saline-alkali stress in foxtail millet (Setaria italica L.)
Scientific Reports (2024)
-
Major transcription factor families at the nexus of regulating abiotic stress response in millets: a comprehensive review
Planta (2024)
-
Reactive oxygen species (ROS) modulate nitrogen signaling using temporal transcriptome analysis in foxtail millet
Plant Molecular Biology (2024)