In poplar (Populus deltoides) a 32kDa bark storage protein (BSP) accumulates during the fall, and is a major form of stored nitrogen during overwintering. This protein is induced by short-day (SD) photoperiod and may play an important role in nitrogen cycling in the plant. To determine the effect of plant nitrogen status upon BSP gene expression, poplar plants were grown in controlled environmental chambers under either SD or long-day (LD) photoperiods and watered with either 5, 10, 50, and 100 mM NH4NO3 for four weeks. [15N]-NH4NO3 was applied during the first and third weeks. SDS-PAGE and western blot analysis were used to detect the relative amounts of BSP. RNA gel blot analysis was used to determine the changes in BSP gene expression. BSP accumulation was enhanced by increasing levels of nitrogen under both photoperiods, however, SD photoperiod appears to moderate the response. These results indicate that BSP gene expression is dependant upon the nutritional status of the plant. [15N] analysis will also be presented.
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