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Expression And Function Of Arabinogalactan-proteins Inxylem Of Loblolly Pine

Genomic and cDNA clones of two genes encoding xylemspecific proteins were previously isolated and characterized. Transcripts of these genes are extremely abundant in differentiating xylem, much less abundant in needles, and are present at very low or non-detectable levels in embryos and megagametophytes. Both genes appear to encode arabinogalactan-proteins (AGPs). AGPs are highly glycosylated proteins thought to play important roles in plant development. AGPs have been found to be abundant in differentiating xylem of loblolly pine. We are attempting to produce genetically engineered loblolly pine plantlets with reduced amounts of these AGPs in order to examine their function in xylem development. Possible roles include cell-cell signalling or cellular interactions, transport of cell wall components, autolysis, or they may act as gums or humectants. We have isolated both promoters and found them to be functional in bombarded pine tissues and in transgenic tobacco, poplar, and white spruce. We are currently searching for the elements responsible for xylem specificity and for the high levels of expression observed. These elements will be of value in future attempts to genetically engineer wood properties.


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Author(s): Carol A. Loopstra, E. G. No, Ronald R. Sederoff

Publication: Tree Improvement and Genetics - Southern Forest Tree Improvement Conference - 1995