Functional effects of inter-genome interactions on seed development in Arabidopsis thaliana
Dupouy, Gilles A.
Dupouy, Gilles A.
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Publication Date
2022-01-14
Type
Thesis
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Abstract
Plant seed size determination is of high economic interest for modern food production worldwide as many crops are mainly consumed in the form of seeds, such as rice, wheat or corn. Parental conflict and genomic imprinting have been intensively studied during the last 20 years with many reports of their manifestations to significantly affect seed size determination in plants. However it has so far mostly been studied from the point of view of the nuclear genome leaving out the organelle genomes from the mitochondria and the chloroplast. In this Ph.D. thesis we explore how the interactions between these genomes can post-zygotically influence the development of seeds in angiosperms using the plant molecular model Arabidopsis thaliana. After establishing a state-of-the-art of the current knowledge on the molecular manifestations of maternal-paternal conflict over the energy allocated to the offspring, I studied the effect of these genomic interactions using different approaches. I first studied the impact of parentally imprinted genes under positive Darwinian selection on the development of intra-species hybrid seeds of A. thaliana and revealed an essential role of the CHD3 chromatin remodeler PICKLE RELATED 2 (PKR2) on the establishment of post-hybridity F1 seed size heterosis in disregard to its imprinting status. I further studied the evolution of PKR2 in comparison to its paralog PKL and showed that PKR2 is under a process of neofunctionalization since its apparition in the Brassicaceae lineage after the duplication of PKL, explaining their previously reported antagonistic effects on seed size in A. thaliana. I then explored the impact of a disruption of cytonuclear relationships (cybridity) and showed that cybridity and hybridity have an additive effect on F1 seed size determination. Finally, I performed a case-study on the impact of cytonuclear relationships on seed development by characterising the gene PLASTID RIBOSOME PROTEIN L5 and have shown it to be necessary for post-globular embryo development in A. thaliana. These results highlight the interconnection of the different plant genomes for seed size determination as well as its importance for future plant breeding programs.
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NUI Galway