Proline, Hydroxyproline, and Lily Pollen Tube Elongation |
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Authors: | DASHEK W V; HARWOOD H I |
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Institution: | 3Department of Biology, Virginia Commonwealth University Richmond, Virginia 23220, U.S.A.
4Department of Biology, Boston University Boston, Massachusetts 02215, U.S.A. |
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Abstract: | Cytoplasm of freshly-harvested, ungerminated Lilium longiflorum,cv. Ace pollen contains 0.14 per cent soluble and 0.35 per centprotein-bound proline (pro). Their metabolic fates in germinationand tube elongation are not known with certainty. Here is reportedconversion of pro to hydroxyproline (hyp)containing constituentsas well as distribution and isolation of these constituents.Colorimetry revealed pro and hyp in wall, trichloroacetic acid(TCA)precipitable, and TCA-soluble cytoplasmic fractions.A balance sheet summarizing quantitative changes in pro andhyp for these fractions revealed that TCAprecipitablecytoplasmic pro could be a precursor to wall-bound pro and asubstrate for hydroxylation yielding cytoplasmic and wall-boundhyp. To determine whether hyp was a component of tube and/orgrain walls, pollen was allowed to germinate 1.5 h and thentransferred to sorbitol medium which prevented further tubeelongation. Hyp was absent from walls of transferred pollen.Electron microscope autoradiography of tubes exposed to 2H-prosuggested that a pro- and/or hyp-containing constituent waslocalized in the growing tip. Light microscope autoradiographyof intact tubes labelled with 14C-pro showed that the constituentwas distributed throughout the pollen tubes. Gel filtrationof hyp-containing material enzymically released from walls supportedthe view that they contained hyp-glycopeptides. |
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