SWEETs: Mechanistic model of sucrose allocation in grains of barley and rice
Final Report Abstract
We have characterized the SWEET gene family in barley and determined the key SWEETs involved in the grain filling process. Using a multidisciplinary approach which included transport activity assays using Xenopus oocytes, the generation of loss-of-function mutants, SWEET-repressed plant lines (RNAi), magnetic resonance imaging, LC/MS, FTIR-imaging and flow cytometry we characterised the function of distinct SWEET proteins in sucrose allocation in the developing grain. A novel additional feature of SWEETs was discovered - the transfer of cytokinin. The dual function of HvSWEET11b in the transport of both sugar and cytokinin likely predetermines their synergistic role, resulting in appropriate adjustments to both the grain’s biochemistry and transcriptome. Our study on RNAi-mediated repression of HvSWEET11b corroborated own previous hypotheses, and provided experimental evidence for its involvement in the dynamic of sucrose allocation in the grain. The grains of the transgenic plants showed changed gradients of cytokinin and sucrose within the grain tissues, and altered cell numbers that affect various seed traits. Barley plants harbouring a loss-of-function mutation of HvSWEET11b were unable to set viable grains. Comparative studies of barley versus rice led to the establishment of a novel, more accurate MRI procedure to trace sugar allocation within the grains. Preliminary results revealed some peculiarities in sucrose allocation in the rice grain, which could partly explain the distinct expression pattern of SWEETs in these plants. Advanced understanding of the SWEET functionality in barley and rice and technological improvements made in frame of this project provide a base and new perspective for investigations on yield formation in cereal crops.
Publications
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(2017) A chromosome conformation capture ordered sequence of the barley genome. Nature 544: 427-433
Mascher et al. (coauthored by V. Radchuk and L. Borisjuk)
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(2018) Micro imaging displays the sucrose landscape within and along its allocation pathways. Plant Physiol 178: 1448-1460
Gündel A, Rolletschek H, Wagner S, Muszynska A, Borisjuk L
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(2019) A tiered approach to genome-wide association analysis for the adherence of hulls to the caryopsis of barley seeds reveals footprints of selection. BMC Plant Biol 19: 95
Wabila C, Neumann K, Kilian B, Radchuk V, Graner A
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(2019) Clubroot disease stimulates early steps of phloem differentiation and recruits SWEET sucrose transporters within developing galls. Plant Cell 30: 3058-3073
Walerowski P, Gündel A, Yahaya N, Truman W, Sobczak M, Olszak M, Rolfe SA, Borisjuk L, Malinowski R
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(2019) The highly divergent Jekyll genes, required for sexual reproduction, are lineage specific for the related grass tribes Triticeae and Bromeae. Plant J 98: 961-974
Radchuk V, Sharma R, Potokina E, Radchuk R, Weier D, Munz E, Schreiber M, Mascher M, Stein N, Wicker T, Kilian B, Borisjuk L
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(2020) Adaptation strategies of halophytic barley Hordeum marinum spp marinum to high salinity and osmotic stress. Int J Mol Sci 21: 9019
Isayenkov S, Hilo A, Rizzo P, Tandron Moya YA, Rolletschek H, Borisjuk L, Radchuk V
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(2020) Advances in the understanding of barley plant physiology: factors determining grain development, composition and chemistry. In: Achieving Sustainable Cultivation of Barley (Eds. G. Fox and C. Li), Burleigh Dodds Sci. Publ. (Burleigh Dodds Series in Agricultural Science, Vol. 74), Cambridge, UK, pp. 1-44. ISBN 978-1-78676-308-2
Borisjuk L., Rolletschek H., Radchuk V.
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(2021) Grain filling in barley relies on developmentally controlled programmed cell death. Comm Biol 4: 428
Radchuk V, Tran V, Hilo A, Muszynska A, Gündel A, Wagner S, Fuchs J, Hensel G, Ortleb S, Munz E, Rolletschek H, Borisjuk L
