Date of Award


Document Type


Degree Name

Bachelor of Arts

First Advisor

Rouhier, Kerry


The successful growth of a plant is dependent upon the resources available to it at germination. The majority of these resources come in the form of storage lipids and proteins accumulated in the tissues over the course of the seed‰Û÷s development. During germination the embryo mobilizes these storage compounds to sustain its growth until it is able to perform photosynthesis. Amongst the enzymatic components active during reserve mobilization, a key enzyme in valine degradation stands out as being active during seed development as well. Methylmalonate semialdehyde dehydrogenase (MMSDH) catalyzes the conversion of methylmalonate semialdehyde into propionylCoA and of malonate semialdehyde into acetyl-CoA, a key component of biosynthesis. In Oryza sativa MMSDH-knockout mutants exhibited poor cell expansion, but in an Arabidopsis MMSDH-knockout mutant the phenotype of wrinkled seed coats and poor germination resemble the oil-deficient wrinkled1 mutant. Physical dimensions of whole seed and dissected embryos showed the mutant embryo to be smaller and lighter than wild-type. Fatty acid content in whole seed and dissected seed components measured by gas chromatography-mass spectrometry revealed the mutant seed to be significantly lower in global lipid content. The ratio of embryo to seed coat fatty acids was decreased in aldh6b2 seeds, suggesting that the embryo is more affected by the mutation than the maternally-derived seed coat. Protein content was elevated in aldh6b2; a lipid-protein compensatory phenotype has been observed in other low-oil mutants. These data point towards an unprecedented metabolic interaction between MMSDH and seed maturation mechanisms.


Includes bibliographical references (p. 22-25)

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