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Expression of trehalose-6-phosphate phosphatase in maize ears improves yield in well-watered and drought conditions

Abstract

Maize, the highest-yielding cereal crop worldwide, is particularly susceptible to drought during its 2- to 3-week flowering period. Many genetic engineering strategies for drought tolerance impinge on plant development, reduce maximum yield potential or do not translate from laboratory conditions to the field. We overexpressed a gene encoding a rice trehalose-6-phosphate phosphatase (TPP) in developing maize ears using a floral promoter. This reduced the concentration of trehalose-6-phosphate (T6P), a sugar signal that regulates growth and development, and increased the concentration of sucrose in ear spikelets. Overexpression of TPP increased both kernel set and harvest index. Field data at several sites and over multiple seasons showed that the engineered trait improved yields from 9% to 49% under non-drought or mild drought conditions, and from 31% to 123% under more severe drought conditions, relative to yields from nontransgenic controls.

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Figure 1: Production of transgenic maize containing the OsMads6-Tpp1 trait.
Figure 2: Metabolic and biochemical characterization of OsMads6-Tpp1 ear spikelets.
Figure 3: Field performance summaries for several OsMads6-Tpp1 events.
Figure 4: Change in field trial yield outcome due to the OsMads6-Tpp1 trait.
Figure 5: Correlation analysis of trait components for OsMads6-Tpp1 events in the 2006 greenhouse study.

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Acknowledgements

We thank E. Cates and M. Yarnall for technical assistance. L. Payan, C. Chaulk-Grace and L. Mansur managed the field trial locations. We also thank our Syngenta colleagues for their enthusiasm and support of this work. We thank M.-D. Chilton and the anonymous reviewers for helpful comments. Trehalose metabolite measurements were done by Metabolon. Rothamsted Research receives strategic funding from the Biotechnological and Biological Sciences Research Council of the U.K.

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Authors

Contributions

M.L.N. and L.M.L. conceived the study. M.L.N. designed the trait constructs and did the molecular characterization of the transgenic events. X.C. contributed to vector construction and event characterization. J.W. designed and conducted the greenhouse water deficit studies. H.-P.Z. and M.M. designed and managed the MSE and agronomic trials. Y.G. did the trait protein characterization. L.F.P. sampled for metabolite measurements, performed the SnRK1 assays and contributed to the histochemical analysis of the OsMads6 expression cassette. S.S.B. and E.H. performed the metabolite analysis. R.M. did the statistical analysis. M.L.N. and M.J.P. wrote the paper.

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Correspondence to Michael L Nuccio.

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Competing interests

This work was funded by Syngenta, a for-profit agricultural technology company, as part of its research and development program. M.L.N., J.W., H.-P.Z., M.M., X.C., Y.G., E.H., S.S.B. and L.M.L. were Syngenta employees when contributing to this work. Some of the data were used in the following U.S. patents: 8,129,588; 8,597,913; and 8,679,844.

Integrated supplementary information

Supplementary Figure 1 Binary vectors used to make supporting transgenic plants for this study.

Maps of the binary vectors used to make (a) OsMads6-GUS, (b) OsMads13-GUS and (c) OsMads13-Tpp1 events. Going counter clockwise the abbreviations are RB, the T-DNA right border; oCOLE, the E. coli origin of replication; oVS1 origin of replication that functions in Agrobacterium tumefaciens; cRepA, cRepA, pVS1 replication protein; cVirG, Agrobacterium virulence factor that enhances transformation; cSpec, bacterial selectable marker that confers resistance to spectinomycin; LB, the T-DNA left border, tNOS, the transcriptional terminator for the plant selectable marker gene; cPMI, the E. coli phosphomannose isomerase coding sequence which is the plant selectable marker; and prUbi1, the plant selectable marker promoter based on the maize Ubiquitin 1 gene. For the trait-specific genes, green arrows designate promoters, blue arrows designate protein coding sequence and red arrows designate transcriptional terminators. Vector construction is described in the Online Methods.

Supplementary Figure 2 Sugar metabolite levels in ear spikelets.

Tissue was harvested approximately 5 days before pollination from unstressed (ns) and drought stressed (ds) plants. The metabolites are (a) UDPG, UDP-glucose; S6P, sucrose-6-phosphate; trehalose and (b) G6P, glucose-6-phosphate. Data are the mean ± s.e.m. (n=4 or 5) of independent measurements. Data that are significantly different between transgenics and wildtype are indicated: * (P < 0.05), ** (P < 0.01). (c) Chart showing P values using Dunnett’s procedure for linear contrasts, between data from transgenic events and wildtype, for each measured metabolite.

Supplementary Figure 3 Plot layout in the 2004 CA field trail.

The location of OsMads6-Tpp1 events in each rep is shown. Data are from the (a) well watered block and (b) the water deficit block. Each cell represents a 2-row plot and the data are the plot yield in estimated Mg ha-1 at 15.5% grain moisture. The range and row coordinates are provided to illustrate distance from the irrigation source which is located in front of range 1. Solid colored cells indicate trait plots and uncolored cells containing numbers indicate control plots. Control data for events without a null are the mean of wildtype plots in each rep. The average yield ± standard deviation for each range and row are provided to illustrate field variation. The average yield ± standard deviation for each treatment is provided to illustrate the treatment effect.

Supplementary Figure 4 Pairwise correlations of yield component data from the 2006 greenhouse study water deficit treatment block.

Pairwise correlations and significance probabilities of the yield component data shown in Figure 5 are calculated and plotted for the water deficit treatment block. The results are for all plants (count = 32) in each treatment block. The units are described in Figure 5. These data are summarized in Table 1 and Supplementary Tables 6 and 7.

Supplementary Figure 5 OsMads13 donor gene annotation and expression cassette.

(a) The genomic DNA sequence representing OsMads13 was annotated by cDNA/gDNA alignment. These data were used to design trait gene regulatory components, depicted by the solid black lines. The promoter is on the right and terminator is on the left. The size and orientation of each line indicates gDNA incorporated into each component. Open boxes represent non-transcribed sequence, grey is transcript, large grey boxes are exons, narrow grey boxes are introns. (b) OsMads13 expression cassette activity in T1 maize was assessed by histochemical localization of β-glucuronidase (GUS) protein. The left panels are central, longitudinal- and cross-sections of the ear. The right panel is a stem section taken at the ear node with the ear removed. Samples were harvested 5 days before pollination, and were incubated in the histochemical reagent for various times at 37°C then cleared with ethanol and photographed. The OsMads13 expression cassette is not active, i.e. a histochemical signal is not detected, in other plant tissues including silk, leaf, root and tassel52. The black bar in each image is 5 mm.

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Nuccio, M., Wu, J., Mowers, R. et al. Expression of trehalose-6-phosphate phosphatase in maize ears improves yield in well-watered and drought conditions. Nat Biotechnol 33, 862–869 (2015). https://doi.org/10.1038/nbt.3277

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