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Title: Analysis of targeted CYCD7;1 expression in seed development
Author: Sornay, Emily
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2013
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D-type cyclins in plants are represented by seven conserved subgroups and play a major role in controlling cell division. Relatively little is understood of their role during seed development, although their expression pattern has been characterized and ectopic expression of CYCD3;1 has previously been shown to disrupt normal embryo development. Here the consequences of ectopic expression of CYCD7;1 using the early endosperm-specific promoter FWA in developing Arabidopsis seeds were investigated. Ectopic CYCD7;1 expression in the maternal central cell prior to fertilization, and in the endosperm from fertilization until cellularization resulted in seeds up to 45% larger. Seed enlargement was accompanied seed lethality, shown to be due to a defect of development during early and mid stages of seed development. As expected from the maternal specific expression of the imprinted FWA promoter, seed size and lethality was dependent on maternal origin of the transgene. Larger seed size was correlated to mature embryo and seed coat outgrowth, and was due to cell proliferation rather than cell elongation. In particular, embryo development was accelerated during the early stages, suggesting these may be dependent on cell division rate, whereas later stages progressed at the same rate as WT seeds. Seed-targeted CYCD7;1 expression phenocopies (1) the nucleus proliferation in the endosperm prior to fertilization observed in rbr and fis-class mutants and (2) the seed enlargement observed in paternal genome excess interploidy crosses. These suggest that CYCD7;1 may act through the RBR pathway to promote cell proliferation and modify imprinting in the endosperm, thereby influencing the parental genome balance. Mechanistically, CYCD7;1 did not interact directly with CDKA;1 but the interaction was promoted in presence of the inhibitor of CDK, ICK1/KRP1 or ICK2/KRP2 in a yeast-three-hybrid assay. However, loss of either KRP1 or KRP2 in respective mutant backgrounds did not prevent the seed enlargement phenotype.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Q Science (General) ; QH301 Biology