Exploring the genetic and transcriptomic regulation of stigma development and senescence in bread wheat

Millán Blánquez, Marina (2023) Exploring the genetic and transcriptomic regulation of stigma development and senescence in bread wheat. Doctoral thesis, University of East Anglia.

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In the absence of pollination, the floral stigma senesces, which leads to an irrevocable loss in the reproductive potential of the flower directly affecting seed set. In self-pollinating crops like wheat (Triticum aestivum), the post-anthesis viability of the unpollinated carpel has been overlooked, despite its importance for hybrid seed production systems. The overall aim of this thesis is, therefore, to explore the mechanisms underlying stigma development and senescence in the absence of self-pollination.

To advance our knowledge of stigma development in the absence of pollination, we have created a high-throughput phenotyping approach that combines light microscopy and machine learning to examine stigma growth and senescence. By applying this method, we show that the unpollinated carpel undergoes a well-defined initial growth phase, followed by a peak phase (in which stigma area reaches its maximum), and a final deterioration phase marked by the upregulation of senescence-related genes. We next examine the impact of varying onsets of stigma deterioration on cross-pollination rates under field conditions across two years. Our findings indicate that hybrid seed set remains stable within a 10 to15-day pollination window, aligning closely with the end of the peak phase of stigma development. Finally, to uncover the genetic mechanisms controlling stigma development, we conduct RNA-sequencing using unpollinated stigmas. This analysis reveals three distinct gene expression waves corresponding to the defined growth, peak, and deterioration phases. Among 66 identified transcription factors expressed predominantly during stigma senescence, the wheat orthologs of Arabidopsis NAC TFs KIRA1 (KIR1) and ORESARA1 (ORE1) emerged as potential regulators. Phenotypic characterisation of kir1 and ore1 mutants indicated a modest extension of stigma longevity but no significant improvement in seed set under controlled conditions.

In essence, this thesis offers breeders and researchers a new framework for advancing mechanistic insights into female fertility in wheat, thereby laying the groundwork to improve hybrid wheat seed production.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Chris White
Date Deposited: 20 Mar 2024 14:14
Last Modified: 20 Mar 2024 14:14
URI: https://ueaeprints.uea.ac.uk/id/eprint/94731

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