|Samac, Deborah - Debby|
Submitted to: Midwest Rhizosphere Research Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2003
Publication Date: N/A
Technical Abstract: White lupin grown under phosphorus (P) deficient conditions undergoes synchronized changes in gene expression which lead to strikingly modified root development and an altered rhizosphere. In P-limited environments white lupin develops clusters of tertiary lateral roots (proteoid/cluster) which exude copious amounts of organic acids and proteins into the rhizosphere. Exudation of organic acids and acid phosphatase enzyme into the rhizosphere functions in facilitating the release or solubilization of P from inorganic and organic complexes, respectively. Macroarray expression studies of more than 2,000 ESTs isolated from P-stressed roots of white lupin showed: 1) steady state amounts of some 40-50 genes are enhanced by P stress; 2) genes involved in root carbon metabolism directed toward organic acid synthesis are, in general, up-regulated by P stress; 3) genes specifically related to P acquisition, acid phosphatase and Pi transporters, have enhanced message abundance in P stress induced proteoid roots; and 4) a potential anion transporter belonging to the MATE family of proteins has 5- to 7-fold increased abundance under P stress. Genes, including the 5'-upstream region of several P responsive genes were isolated and sequenced. Potential P responsive elements were identified. The 5'-upstream putative promoter region of white lupin genes that respond to P stress effectively drive the expression of a GUS reporter in transgenic Medicago sativa and in hairy roots of white lupin. Recent studies implicate products of photosynthesis in regulation of P-stressed gene expression.