Deciphering molecular mechanisms controlling seed development under low energy stress
Final Report Abstract
Plant reproduction is a highly plastic agronomic trait, which is sensitive to the plant’s photoassimilate (carbohydrate, C) and organic nitrogen (N) supply. To coordinate this highly resource demanding process as well as adjusting it to in- and extrinsic cues a sophisticated regulatory network is required. While hormones such as auxin have been well-established to be involved in plant reproduction processes such as control of seed development and shoot branching, accumulating evidence suggests a prime importance of C availability in triggering these developmental decisions. Therefore, we aimed to identify and functionally characterise transcriptional regulators that are capable to integrate information on the prevailing C status into reproductive organ formation. Employing single and higher-order mutant combinations as well as inducible overexpression approaches of group S1 basic-leucine-zipper (S1-bZIP) transcription factors (TFs), we disclosed their largely redundant function in establishing growth dominance of the primary inflorescence and proper seed set. In this respect, comprehensive tissue-specific metabolite analyses revealed a clear shift of C and N allocation from apical to lateral organs in S1- bZIP mutants, suggesting that these regulators are essential to focus these resources to the primary inflorescence. Making use of a combination of tissue-specific transcriptomics, transactivation studies and DNA-binding assays, we disclosed specific SWEET sugar export facilitators that are involved in long-distance sugar transport from source leaves to apical sinks and a central glutaminase as direct S1-bZIP targets, while mutant analysis of these downstream genes further validated their impact on the S1-bZIP associated shoot branching phenotype. As we found group S1 bZIP11 levels to be controlled by trehalose-6-phosphate, a signaling sugar that is proposed to mirror sucrose availability, S1 bZIPs are well-suited candidates to convey C dependent developmental plasticity of shoot branching, thereby allowing a high seed yield under favorable growth conditions but ensuring proper seed supply even under detrimental ones.
Publications
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The transcription factor bZIP11 acts antagonistically with trehalose 6-phosphate to inhibit shoot branching.
Hellens, A. M.; Kreisz, P.; Humphreys, J. L.; Feil, R.; Lunn, J.E.; Dröge-Laser, W.; Beveridge, C. A.; Fichtner, F.; Weiste, C. & Barbier, F. F.
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S 1 basic leucine zipper transcription factors shape plant architecture by controlling C/N partitioning to apical and lateral organs. Proceedings of the National Academy of Sciences, 121(7).
Kreisz, Philipp; Hellens, Alicia M.; Fröschel, Christian; Krischke, Markus; Maag, Daniel; Feil, Regina; Wildenhain, Theresa; Draken, Jan; Braune, Gabriel; Erdelitsch, Leon; Cecchino, Laura; Wagner, Tobias C.; Ache, Peter; Mueller, Martin J.; Becker, Dirk; Lunn, John E.; Hanson, Johannes; Beveridge, Christine A.; Fichtner, Franziska ... & Weiste, Christoph
