Discrete proteins associated with overwintering of interior spruce and Douglas-fir seedlings

Abstract

Seasonal protein changes were followed in seedlings of interior spruce (a mixture of Picea glauca and P. englemannii) and Douglas-fir (Pseudostuga menziesii) by sodium dodecylsulfate – polyacrylimide gel electrophoresis. A 30-kDa protein in seedlings of Douglas-fir and a 30- and 27-kDa protein in interior spruce that were not detected in the late summer accumulated in seedling tissues during the fall. These proteins remained present throughout the winter but declined rapidly in seedlings during the initial flush of spring growth. There was an increase in the total protein content of interior spruce seedling tissues during the fall; however, the accumulation of the 30- and 27-kDa protein was tissue specific, since it increased in the apical bud, shoot, and root tissue but not in the leaves. By late fall these proteins represented approximately 15% of the total seedling protein. Measurements of variable chlorophyll fluorescence indicated that the accumulation of these overwintering proteins was associated with the seasonal decline in photosynthetic capacity. These results suggest that conifer seedlings may utilize these proteins as a storage reserve during overwintering. Key words: conifers, electrophoresis, overwintering, proteins, seasonal, seedlings.