Date of Award


Degree Type


Degree Name

Master of Science




Dr. Frédéric Marsolais

Second Advisor

Dr. Denis Maxwell

Third Advisor

Dr. Mark Bernards


Soybean (Glycine max [L.] Merr.) is an important crop grown primarily as a protein and oil source. Asparagine is the main form of organic nitrogen that is transported to developing seeds during seed filling in soybean and other legumes. Asparaginase (ASPG) is considered to be the major enzyme metabolizing transported asparagine in the seed coat and developing cotyledon for the synthesis of other amino acids. Beside ASPG, there is evidence for concurrent expression of asparagine synthetase (AS) enzyme in developing seeds. The determination of free asparagine at mid-maturation in three genetically related cultivars (Maple Arrow, AC-Hercule and AC-Proteus) varying in protein content confirmed its positive correlation with seed protein content (SPC). Further, free amino acid profiles of two parental and eight recombinant inbred lines (RILs) differing at four quantitative trait loci (QTL) determining SPC revealed that the high free asparagine trait is associated with two major QTLs. The relationship between AS and ASPG expression and SPC was investigated in Maple Arrow and AC-Proteus, in developing seed coat and cotyledons from growth-chamber grown plants, and in whole seeds from field-grown plants by immunoblots and RT-PCR experiments. In addition, tissue-specific overexpression of PvASPG2 in developing cotyledons decreased total amino acids and nitrogen content in seeds at maturity. These results demonstrate that both AS and ASPG might play a significant role in the regulation of SPC in soybean.



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