Molecular Basis of Growth in Plants: Probing the Role of Wall Polysaccharides and Their Metabolism by Wall Proteins

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Plant cell elongation is an expression of metabolic changes that alter load bearing bonds within the wall to allow molecular displacement under the influence of internal pressures. Specifically, the proposal addresses the hypothesis that specific wall polysaccharide structures are modified in such a manner that such load bearing bonds are affected. The assay system utilized will be the Zea mays coleoptile. The major directions the proposal explores include: 1) The development of an in vitro system to quantitatively evaluate polysaccharide binding to cellulose. This model will allow a determination of the extent to which binding is affected by pH and the effect of pH after modification of structures by enzymes. 2) The experiments will extend the observation that antibodies are powerful probes to explore cell wall metabolism. The results derived from application of a family of glucan and glucanase antibodies will be extended to determine the consequences of exposure of tissue to glucuronoarabinoxylan antibodies. The behavior of ferulic acid and the role of diferulic acid linked to these molecules will be assessed. 3) An important component of (2) will be the application of a new enzyme mechanism, using glucuronoxylanase (previously called feraxanase), to modify glucuronoarabinoxylans to determine structure (especially glucuronic acid and ferulic acid components). A second emphasis is based on the observation that spatial (directional) application of antibodies is important in their capacity to suppress growth. This effort will help to determine the role of the epidermis in controlling elongation. Structural and metabolic aspects will also be examined in isolated epidermal cell walls. The experiments described in this proposal will help to elucidate the molecular mechanism of plant growth.//