Abstract
SUMO protein is conserved in all eukaryotic organisms. SUMOylation involves a cascade of enzymatic reactions which alters target protein stability, sub-cellular localization, and protein-protein interactions through the reversible covalent attachment and affects the overall biochemical reaction chains. SUMOylation/ deSUMOylation may function in concert to regulate signaling, development, hormonal responses, biotic and abiotic stress responses in plants. SUMOylated proteins were found to accumulate in various plant tissues under different environmental stress. This thesis aimed to study the role of SUMO and SUMOylation in plants under abiotic stress. To fulfill our purpose, the PaSUMO recombinant protein was produced in Escherichia coli to raise a polyclonal antibody for SUMO detection. Upon subject to cold, heat, drought, salinity and ABA treatments, only cold stress induced accumulation of high molecular weight SUMOylated proteins in our protein blots. The induced SUMOylation in the tropical plant Phalaenopsis aphrodite under cold stress may lead to protein stabilization and protection from degradation. Among all the tissues examined, the half-opened flower displayed the highest level of PaSUMO conjugates. Our result also suggests that SUMOylation process may participate in floral transition.