In plants and other eukaryotes, mitogen-activated protein kinase (MAPK) cascades are essential signalling pathways that regulate a wide array of cellular functions related to development and environmental stress management responses. MAPK cascades each consist of a chain of kinases ranging from MAPKKKKs to MAPKs, which upregulate downstream kinases by phosphorylation to elicit cellular responses. Ultimately, the cellular output of MAPK signalling is primarily controlled by MAPK phosphatases (MKPs), which downregulate MAPKs by dephosphorylation. The five MKPs identified in Arabidopsis thaliana (MKP1, MKP2, DsPTP1, IBR5 and PHS1) have primarily been found to be involved in plant stress responses, making our knowledge of the involvement of these phosphatases in developmental pathways limited. Our research group previously found that MKP2 and DsPTP1 exhibit a striking albino phenotype characterized by small cream-coloured seedlings when both are absent in double mutants. In this thesis, I further characterize the roles of MKP2 and DsPTP1 in plant growth and development and identify potential MAPK substrates of the two phosphatases. In-silico transcript and protein accumulation studies were performed and reveal the expression of MKP2 and DsPTP1 in vegetative tissues, indicating their possible role in the early stages of plant development. To identify potential MAPK substrates, yeast two-hybrid and bimolecular fluorescence complementation studies were performed. Based on my analyses, I propose four MAPKs that are potential targets of MKP2/DsPTP1 in a pathway that regulates plant development. In summary, this work characterizes potential roles of MKP2 and DsPTP1 in plant development and identifies potential MAPK substrates for further study.