© 2001 Heron Publishing—Victoria, Canada
Ecotypic and genetic variation in poplar bark storage protein gene expression and accumulation
Brent L. Black (1, 3), Cécile M. Parmentier-Line (1), Leslie H. Fuchigami (2) and Gary D. Coleman (1, 4)
1. Department of Natural Resource Sciences and Landscape Architecture, and Program in Molecular and Cellular Biology, 2102 Plant
Sciences Building, University of Maryland, College Park, Maryland 20742-4452, USA / 2. Department of Horticulture, Oregon State University, Corvallis, Oregon 97331-7304, USA / 3. Fruit Laboratory, Plant Science Institute, United States Department of Agriculture, Beltsville, MD 20705-2350, USA / 4. Author to whom correspondence should be addressed (gc76@umail.umd.edu) / Received April 18, 2001
Summary
Bark storage proteins (BSP) store nitrogen (N) translocated from senescing leaves in autumn, and supply reduced N for spring
growth. Expression of bsp and BSP accumulation are associated with short day photoperiod. To determine if photoperiod-associated bsp expression varies among poplars native to different latitudes, Populus deltoides Bartr. clones originating from six latitudes were grown under natural conditions at a common location. Relative amounts of
BSP mRNA in these clones were measured at 2-week intervals from August 7 to October 16. The date of maximum BSP mRNA accumulation
was correlated with latitude of origin, and maximum accumulation of BSP mRNA occurred earlier in clones native to northern
latitudes than in clones native to southern latitudes. This pattern of variation is consistent with photoperiodic responses
of plants native to temperate climates. Genotypic variations in BSP accumulation, bark protein concentration and bark N concentration
were compared among clones of six hybrid poplar (Populus trichocarpa Torr. and Gray × P. deltoides) full-sib families (three F2 families, two F1 families and one BC1 family) after 6 weeks in a short day photoperiod and at midwinter. Significant differences in BSP accumulation occurred among
clones within four of the six full-sib families after 6 weeks in a short day photoperiod and also at midwinter for outdoor-grown
plants. Bark protein and bark N concentrations also varied significantly among clones within certain families. In general,
the greatest variation was found in F2 and BC1 families. Within several families, relative BSP amounts were positively correlated with bark protein concentration and total
bark N concentration. These results indicate a role of photoperiod in regulating bsp expression and demonstrate a genetic component underlying seasonal BSP accumulation. The results could have significance
in selecting for clones with improved N storage capacity and N-use efficiency.
Keywords:
nitrogen, photoperiod, seasonal growth transition, vegetative storage protein.
