Studies On Proteinaceous Protease Inhibitor And Its Relationship With Desiccation Tolerance And Vigour Of Peanut (Arachis Hypogaea L.) Seeds

Peanut (Arachis hypogaea L.cv. Yueyou 116) seeds were chosen as materials in this thesis to study the general characteristics of the natural proteinaceous protease in-hibitors from them The models of biosynthesis or accumulation and degradation of the inhibitors during development, imbibition and germination had also been investigated by which to explore the relationships between the inhibitors and desiccation tolerance or vigour of the peanut seeds.Protease inhibitors in the peanut seed are mainly contained in the embryo without cotyledon (zygotic embryo) due to their content was as 6 -7 times as that of cotyledon. Two chief isoinhibitors with Mr of 5,000~8,000 and pi of 4. 3 and 4. 6, respectively, were found and might exist as dimer. The inhibitor is a member of Bowman—Birk family because of the specificity for its substrate, the much lower Mr and other physical and biochemical features. With great resistance to heat—treatment and acid environment or highly hydrophility, the inhibitor strongly inhibited the activity of trypsin and slightly decreased that of leucine aminopeptidase as well. The 2S albumins from peanut seed contained a component inhibiting the trypsin activity. The target protease the fluorescence waves of excitation and emission and the behavior in SDS-PAGE or 2D-PAGE of the component showed that it was the same protein as the trypsin inhibitor described above-To investigate the biosynthesis rate and inhibitory activity changes of the TIPS (trypsin inhbitors from peanut seed) during development, zygotic embryos at different developing stages were dually labeled by ~3H- Leu and ~3H-Tyr. Both labeled or non-labeled zygotic embryos or non—labeled cotyledons were used for extracting and testing the inhibitors. Results indicated that the TIPS were begun to biosynthesize at early stage of development. During middle stage, there was an extreme increase of biosynthetic rate and accumulation for the TIPS which got to the highest level at 45DAP (days after pegging) following a rapid decrease during late developing period. The UIA (units of inhibitory activity) of TIPS from zygotic embryos had been rapidly declining to a lower...