Japanese chestnut (Castanea crenata) agglutinin may have a role as vegetative storage protein

The expression of Japanese chestnut (Castanea crenata) agglutinin (CCA) and its mRNA was investigated in nitrogen-fertilized young potted plants and in floral organs of adult trees. Two levels of N were used: 10 and 20 mM NH4NO3. Both levels increased protein content in all vegetative organs, though the magnitude of the increase differed. The highest increase was observed in stems. High levels were retained in 20 mM N-fertilized plants, whereas the protein content decreased at 10 mM N fertilization. Expression of CCA and its mRNA was observed in young leaves and stems, and their quantities depended on the amount of N fertilizer supplied. In mature leaves, CCA was detected in the first 4 weeks, but its mRNA was undetectable throughout the experimental period. Neither CCA nor its mRNA was detected in roots. In floral organs, CCA and its mRNA were expressed throughout the flower but their quantities differed. These results suggest that CCA acts as a vegetative storage protein, which functions in temporary nitrogen reserve. The results also suggest that expression of CCA is regulated at both transcriptional and translational levels.