High expression of the MADS-box gene VRT2 increases the number of rudimentary basal spikelets in wheat

Backhaus, Anna E., Lister, Ashleigh, Tomkins, Melissa, Adamski, Nikolai M., Simmonds, James, Macaulay, Iain, Morris, Richard J., Haerty, Wilfried ORCID: https://orcid.org/0000-0003-0111-191X and Uauy, Cristobal (2022) High expression of the MADS-box gene VRT2 increases the number of rudimentary basal spikelets in wheat. Plant Physiology, 189 (3). pp. 1536-1552. ISSN 0032-0889

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Abstract

Spikelets are the fundamental building blocks of Poaceae inflorescences, and their development and branching patterns determine the various inflorescence architectures and grain yield of grasses. In wheat (Triticum aestivum), the central spikelets produce the most and largest grains, while spikelet size gradually decreases acropetally and basipetally, giving rise to the characteristic lanceolate shape of wheat spikes. The acropetal gradient corresponds with the developmental age of spikelets; however, the basal spikelets are developed first, and the cause of their small size and rudimentary development is unclear. Here, we adapted G&T-seq, a low-input transcriptomics approach, to characterize gene expression profiles within spatial sections of individual spikes before and after the establishment of the lanceolate shape. We observed larger differences in gene expression profiles between the apical, central, and basal sections of a single spike than between any section belonging to consecutive developmental time points. We found that SHORT VEGETATIVE PHASE MADS-box transcription factors, including VEGETATIVE TO REPRODUCTIVE TRANSITION 2 (VRT-A2), are expressed highest in the basal section of the wheat spike and display the opposite expression gradient to flowering E-class SEPALLATA1 genes. Based on multi-year field trials and transgenic lines, we show that higher expression of VRT-A2 in the basal sections of the spike is associated with increased numbers of rudimentary basal spikelets. Our results, supported by computational modeling, suggest that the delayed transition of basal spikelets from vegetative to floral developmental programs results in the lanceolate shape of wheat spikes. This study highlights the value of spatially resolved transcriptomics to gain insights into developmental genetics pathways of grass inflorescences.

Item Type: Article
Additional Information: Funding Information: This work was supported by the UK Biotechnology and Biological Sciences Research Council (BBSRC) through the grant BB/S016945/1, the Designing Future Wheat (BB/ P016855/1) and Genes in the Environment (BB/P013511/1) Institute Strategic Programs and by the John Innes Foundation. Additional funding was provided by the European Research Council (866328). Funding Information: We thank Phil Robinson from Scientific Photography at John Innes Centre (JIC) for taking high-quality images of spikes and spikelets and Tobin Florio (http://flozbox-science.com/) for scientific illustrations for Figure 1. We thank the JIC Field Experimentation and Horticultural Services teams for technical support in field and glasshouse experiments and the JIC Bioimaging facility and staff for their services and technical support. This work was supported by the UK Biotechnology and Biological Sciences Research Council (BBSRC) through the grant BB/S016945/1, the Designing Future Wheat (BB/ P016855/1) and Genes in the Environment (BB/P013511/1) Institute Strategic Programs and by the John Innes Foundation. Additional funding was provided by the European Research Council (866328). Publisher Copyright: © The Author(s) 2022.
Uncontrolled Keywords: physiology,genetics,plant science ,/dk/atira/pure/subjectarea/asjc/1300/1314
Faculty \ School: Faculty of Science > School of Biological Sciences
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Depositing User: LivePure Connector
Date Deposited: 21 Sep 2022 12:30
Last Modified: 27 Sep 2022 08:32
URI: https://ueaeprints.uea.ac.uk/id/eprint/88553
DOI: 10.1093/plphys/kiac156

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