Deciphering molecular mechanisms controlling seed development under low energy stress

• Applicant: Dr. Christoph Weiste
• Subject Area: Plant Genetics and Genomics
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 408153945

Deciphering molecular mechanisms controlling seed development under low energy stressSummary:Seed yield is a major agronomic trait that depends on proper seed development. It is well-established that the early developmental stages, which comprise embryogenesis, are largely controlled by transcriptional regulation mediated by the phytohormone auxin. Besides this, recent studies revealed that environmental stresses that converge on energy deprivation, also exclusively interfere with early seed establishment, resulting in growth repression of siliques and seed abortion. Although this low energy stress (LES) response was characterised to be reversibly and dynamically tuned according to the plants` prevailing energy status, the underlying molecular mechanism is yet unknown.In our previous work, we unravelled that central players of the plant‘s energy management system, namely basic leucine ZIPper 11 (bZIP11) related transcription factors (TF), which are controlled by the pivotal low-energy activated Snf1 Related Protein Kinases 1 (SnRK1s) integrate low-energy related stimuli into auxin-driven meristematic growth processes. This is mechanistically accomplished by controlling expression of specific Aux/IAAs, which constitute negative feedback regulators of auxin signalling, auxin transport and in consequence auxin-driven meristem activity. As bZIP expression was found to result in strongly reduced seed set and bZIP11-related transcripts that underlie energy-dependent posttranscriptional regulation, reveal a distinct accumulation within the early ovule, we assume that a SnRK-bZIP growth regulatory system evolved to adjust auxin-mediated seed development according to the plants‘ prevailing energy reserves. Specifically operating during early and not late developmental stages, this low energy-triggered system could enable channelling of residual energy resources to nearly completed seeds, thereby ensuring survival of plant progeny under LES.To test this hypothesis, we will initially characterize starvation-responsive bZIP expression domains and kinetics throughout embryogenesis. At the defined, bZIP-controlled seed stages, we will study effects of bZIP mis-expression on the embryos’ auxin signalling and morphology under high- and low energy conditions, making use of inducible and constitutive gain- and loss-of-function approaches. The obtained results will unravel the impact of bZIP11-related TFs in starvation-responsive seed development. Finally, we will address the underlying molecular mechanisms by deciphering the transcriptional network downstream of the bZIP regulators, applying a combination of RNAseq and ChIPseq techniques. Taken together, the proposed project will provide essential insights how energy starvation is transduced into seed development. The obtained knowledge will strongly foster basic research on plant stress adaptation processes and, due to its impact on seed yield, support the development of stress tolerant crops.

• DFG Programme: Research Grants