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Title: ECOTYPIC AND GENETIC VARIATION IN POPLAR BARK STORAGE PROTEIN ACCUMULATION

Author
item Black, Brent
item PARMENTIER-LINE, CECILE - UNIVERSITY OF MARYLAND
item FUCHIGAMI, LESLIE - OREGON STATE UNIVERSITY
item COLEMAN, GARY - UNIVERSITY OF MARYLAND

Submitted to: Tree Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Nitrogen is the most limiting nutrient in plant growth. To conserve this limited resource, temperate deciduous perennials transport nitrogen from autumn-senescent leaves back to the stem to be stored for growth the following spring. This seasonal nitrogen storage occurs in the form of bark storage proteins (BSP) in young stems. Improving the efficiency of nitrogen use in woody plants will require an understanding of the factors affecting accumulation of BSP. To determine the factors affecting time of BSP accumulation, BSP gene expression was compared among poplar plants (Populus deltoides) from different parts of North America (ecotypes) growing at a common location. The time of maximum BSP gene expression was correlated with latitude of origin. This shows that BSP accumulation occurs in response to day length and varies with environmental adaptation. To determine the amount of genetic variation in BSP accumulation, short-day and mid-winter BSP levels were compared among plants from six full-sib families of P. trichocarpa x P. deltoides. There were dramatic differences in short day and mid winter BSP accumulation among these clones which was genetically determined, and was closely correlated with nitrogen content. This information can be used by plant breeders to improve nitrogen efficiency of poplar plants in managed agroforestry systems.

Technical Abstract: Bark storage proteins (BSP) store nitrogen (N) translocated from senescing leaves in autumn, and supply reduced N for spring growth. BSP accumulation and the expression of the BSP gene are associated with short-day photoperiod. Plants of Populus deltoides originating from six locations within the mid-western United States were grown under natural conditions at a common location, and BSP mRNA levels were measured at 2-week intervals from 7-Aug to 16-Oct. The time of maximum BSP mRNA accumulation was inversely correlated with latitude of origin. This inverse correlation is consistent with photoperiodic responses of plants native to temperate climates. Amount of short-day and mid-winter BSP accumulation was compared among P. trichocarpa x P. deltoides clones representing six full-sib families. There were significant differences in BSP levels among clones within four of the six full-sib families, after six weeks of short-day photoperiod and at mid-winter for outdoor-grown plants. BSP levels were positively correlated with total bark nitrogen content within full-sib family. These full-sib families which vary in amount of BSP accumulation will provide an important resource for future studies investigating the ecological costs and benefits of BSP accumulation. The work presented here demonstrates genetic variation in both the time and amount of seasonal BSP accumulation.