A cluster of genes in both animals and flowering plants are expressed only from one of the two homologous chromosomes, depending upon whether they are maternally or paternally inherited. This phenomenon is called imprinting, and is in plants mainly restricted to the endosperm in the seed. Genome wide transcription profiling of seeds lacking a paternal contribution to the endosperm, identified a subset of 12 downregulated MADS-box encoding genes that were putative candidates to be novel imprinted genes. Among these genes were the maternally imprinted PHE1 and the newly identified AGL36. In this thesis, mutant lines for eight of these genes were functionally screened for a seed phenotype. No phenotypes were found in any of the lines and further work was thus focused on mutant lines for AGL90 and AGL34, which are paralogs of AGL36. The nature of the insertions was verified for AGL90 and AGL34 insertion lines, and the mutant lines were investigated closely both morphologically and through reciprocal crosses. In a mutant line of AGL34 seed lethality was found, and this was closely investigated through reciprocal crosses. A weak paternal effect was postulated but could not be not verified upon inspecting crossed siliques directly. Expression patterns were studied for AGL28, AGL34 and AGL90 with the help of promoter::reporter and promoter::gene-reporter constructs generated in this thesis. In addition, double mutants between the above mentioned genes and their interacting partners were generated to determine if any of these genes have redundant functions. This work presented in this thesis has identified a robust basis for further in-depth analysis of AGL34 and AGL90. This could in future contribute to the characterization of more MADS box type I genes and provide a better understanding of the mechanisms involved behind complex process of imprinting.