Identification and Characterization of the Seed Storage Proteins from Alfalfa (Medicago sativa)

The major seed storage proteins in alfalfa are medicagin (alegumin-like globulin), alfin (a vicilin-like globulin) anda family of Lower Molecular Weight albumins (LMW₁₃). These comprise30%, 10% and 20%, respectively, of the total extractable proteinfrom cotyledons of mature seeds. Alfin is a heterogeneous oligomericprotein (Mr 150 kD) composed of polypeptides ranging in sizefrom Mr 50 to 14 kD (₁,-₆; 50, 38, 32, 20, 16 and 14 kD, respectively).Medicagin is also a high molecular weight oligomeric protein,but requires high concentrations of salt for solubilization.It is comprised of a family of individually distinct subunits,each composed of an acidic polypeptide (A₁–A₉; Mr 49 to39 kD) linked via disulphide bond(s) to a basic polypeptide(B₁, B₂, B₃; Mr 24, 23 and 20 kD, respectively). This pairingis highly specific and two families are recognizable on thebasis of the B polypeptide (B₃ or B₁/B₂). Subunits (M_r 50–65kD) are assembled as trimers (8S) or larger oligomers (12S–15S)in mature seeds. The lower molecular weight albumins (LMW₁–₃)are acidic (pl<6), and consist of sets of disulphide-bondedpolypeptides (Mr 15 and 11 kD). Key words: Medicago sativa, seed storage proteins, alfin, medicagin     

The Effects of Rapid and Very Slow Speeds of Drying on the Ultrastructure and Metabolism of the Desiccation-Sensitive Moss Cratoneuron filicium (Hedw.) Spruce

The response of the semi-aquatic moss species Cratoneuron filicinumto desiccation varies with the speed at which it loses water.On rehydration following rapid drying the contents of all cellsare considerably disrupted and they become increasingly disorganizedover a 24 h time period. After very slow drying some cells havethe appearance of those after rapid drying, while others maintaintheir integrity, and the internal organization of mitochondriaand chloroplasts is evident The capacity to resume protein synthesison rehydration is reduced after very slow, slow, and rapid drying:the greater the speed of drying the more it is reduced. Rapidwater loss down to 50% of original fresh weight has no irreversibleeffect on protein synthesis. Respiration does not occur on rehydrationafter rapid drying, although failure to maintain sterile conditionsduring measurement of oxygen consumption can lead to artefactsdue to bacterial contamination. The results are contrasted withthose obtained previously from the desiccation-tolerant mossTortula ruralis, and possible reasons for the differences areoutlined.