Poplar Bark Storage Proteins (BSP) are important in storing nitrogen (N)
recovered from autumn-senescent leaves, and supply N for spring growth. Plants of
Populus tremula x P. alba were transformed with a poplar BSP antisense cDNA
fused to a double 35S promoter. Regenerated lines were screened for reduced BSP
accumulation in short day photoperiod, and two lines were selected for further
studies. Under long-day conditions, both BSP-antisense lines were characterized by
larger leaves, longer internodes and slower growth rates, for a net shift in dry-matter
partitioning from stem to leaf. Antisense lines also show reduced N
concentration in leaf and stem tissue, and altered nitrate uptake. Grafting studies
show that these effects on leaf and stem partitioning and N content are determined
by the shoot genotype. These results indicate an important role of BSP in long day
growth and partitioning. BSP-antisense plants did not show altered Nitrate
Reductase activity, as determined by in vivo assay. Wild-type poplar plants were
grown hydroponically on solutions of 0 to 30 mM nitrate, and NR activity
determined on leaf, stem and root tissue. Leaf activity was >20x higher than root or
stem, with the highest activity found in young expanding leaves. NR activity of
both leaves and roots increased with N supply. During autumn, BSP-antisense
leaves abscised earlier than the untransformed wt. Abscised wt leaves contained a
higher proportion of pre-senescent N levels. Comparisons among ecotypes of P.
deltoides and among clones of P. trichocarpa x P. deltoides demonstrated genetic
variation in both time of BSP induction, and amount of BSP accumulation. In six
P. deltoides ecotypes grown at a common site, time of maximum BSP mRNA was
inversely correlated with latitude of origin. Eight to ten clones from each of six
full-sib families of P. trichocarpa x P. deltoides were screened for SD BSP
accumulation. Clonal differences in BSP accumulation were significant in 5 of 6
families, and clones with high BSP levels also had higher total stem N content.
These results further confirm the importance of BSP in autumn N resorption. / Graduation date: 2000
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/33318 |
| Date | 05 July 1999 |
| Creators | Black, Brent L. |
| Contributors | Fuchigami, Leslie H. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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