Growth-Related Esterification of Plant Cell Wall Pectins

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Pectins are major structural polysaccharides of the cell wall in higher plants and are of enormous complexity. They have been thought to play a multiplicity of roles in the biology of the cell in connection with wall hydration, plasticity and cell adhesion. Pectins also appear to be involved in plant defense responses. This project will examine some of the detailed modifications in chemical structure of pectins that take place during cell growth. Particular attention is to be paid to the specific type of esterification of uronic acid residues in maize cells and how this changes as the cells grow. Evidence that the esterified galactosyluronic acid units cannot be completely accounted for by methyl esters leads to the need for further work to characterize more fully these esterified compounds. This project is intended to elucidate details of esterification and how thesse may relate to polysaccharide interactions resulting from the pectin esterifications that are associated with cell enlargement. The cell wall of higher plants is largely responsible for the support of plants and is a major determinant of the form of plants. Plant cell walls comprise of a number of complex polymeric carbohydrates, including cellulose, hemicellulose and pectic compounds. Pectic compounds are polymeric compounds consisting of a series of sugar-acids that are linked together in complex patterns. These pectic compounds undergo subtle changes in their chemical structure during growth, and these changes may play an important role in determining how plant cells are able to grow in size. In this project Dr. Carpita continues his detailed exploration of the chemistry of maize pectins, making use of state-of- the-art technology in fully characterizing these important compounds.***//