Tracing the formation of wheat spikelets through time and space

Backhaus, Anna (2022) Tracing the formation of wheat spikelets through time and space. Doctoral thesis, University of East Anglia.

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Throughout domestication, humans have significantly altered the structure of the wheat (Triticum aestivum L.) spike to increase its yield. Spikelets are the fundamental building blocks of Poaceae inflorescences, and their development and branching patterns determine the inflorescence architectures and grain yield of grasses. Across the wheat spike, not all spikelets produce the same amount of grain: central spikelets produce the most grains, while this gradually decreases acro- and basipetally. The overall aim of this thesis was to understand the differences in spikelet development across the spike, and specifically the genetic and developmental causes of rudimentary basal spikelets in wheat. Basal spikelets are initiated first, yet they fall behind in development and size compared to central spikelets shortly after initiation. Using low-input transcriptomics, we were able to observe larger differences in gene expression profiles between the apical, central and basal sections of a single spike than between consecutive timepoints. We found that SVP (SHORT VEGETATIVE PHASE) MADS-box transcription factors are expressed highest in the basal section and display the opposite expression gradient to flowering genes. Higher expression of SVP (VRT-A2) in the basal sections was associated with increased numbers of rudimentary basal spikelets. Next, we developed a protocol to cultivate wheat meristems ex situ, to image their growth at cellular resolution, and quantify the effect of SVPs on basal spikelet establishment directly. Furthermore, experiments in the field suggested that the abortion of florets within a spikelet is linked to their developmental age, supporting the idea that it is the delayed development of basal spikelets that causes their preferential abortion, and thus rudimentary shape. These results highlight the complexity of transitioning from one developmental program to the next and that such changes in genetic networks do not happen instantly but require a gradual transition, during which the basal spikelets are formed.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Nicola Veasy
Date Deposited: 23 Mar 2023 10:24
Last Modified: 23 Mar 2023 10:24


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