Protein Synthesis and Aminopeptidase Activity in Dormant Sugar Pine Seeds During Stratification and Warm Incubation

Abstract

Summary The capacity for protein synthesis, the activity of leucine-tyrosine aminopeptidase, and the pattern of soluble native proteins were determined for embryos and megagametophyte tissue from dormant sugar pine ( Pinus lambertiana Dougl.) seeds during 90 d of 25 °C warm, moist incubation or 5 °C stratification. The capacity for protein synthesis increased rapidly during the first 7 d in 25 °C embryos and megagametophytes and then decreased gradually through the rest of the 90-d treatment period. However, this protein synthesis at 25 °C occurred independently of germination, as these seeds maintained their dormancy. The capacity for protein synthesis in the 5 °C embryos eventually surpassed the capacity in 25 °C embryos after 60 d but remained significantly lower in the 5 °C than the 25 °C megagametophytes throughout the 90-d period. The pattern of increase in the capacity for protein synthesis in the 5 °C embryos generally paralleled increases in germinability. After about 14 d, the rate of leucine-tyrosine aminopeptidase activity remained higher in both embryos and megagametophytes at 5 °C than at 25 °C. A decline in activity occurred towards the end of the 90-d period. Patterns of native protein bands, as determined by polyacrylamide gel electrophoresis, remained the same in 5 °C and 25 °C embryos and megagametophytes throughout the 90-d period. However, the staining intensity of several individual bands appeared greater in 25 °C embryos than in 5 °C embryos.