Feeding hungry plants: exploring the role of cell wall-targeted purple acid phosphatases in Arabidopsis phosphate acquisition
Phosphorus (P) is a limiting macronutrient that roots must assimilate from the soil as soluble inorganic phosphate (Pi; H2PO4-). The most abundant P fraction of many soils exists as organic P-monoesters unavailable for root uptake until hydrolyzed by secretory purple acid phosphatases (PAPs). Plant PAPs belong to a relatively large multigene family whose specific functions in P-metabolism are poorly understood. Purification, characterization, and identification (via peptide sequencing) of native PAP isozymes upregulated by Pi-starved suspension cell cultures of Arabidopsis thaliana has been complemented by studies of the corresponding loss-of-function pap mutant seedlings. This approach has pinpointed the predominant Pi-starvation inducible (PSI), cell wall (CW) targeted PAP isozymes (AtPAP12, AtPAP17, AtPAP25, and especially AtPAP26) that appear to facilitate Arabidopsis Pi-acquisition from extracellular P-esters. AtPAP26 is secreted into the CW as a pair of differentially glycosylated ‘glycoforms’ (AtPAP26-CW1 and -CW2). AtPAP26-CW2 is a high mannose glycoform that interacts with a PSI, CW lectin (curculin). This is the first time that glycoforms or a lectin have been implicated in the plant Pi starvation response. The objective of my PhD thesis is to further our understanding of biochemical and functional properties of CW-targeted PAPs of Pi-deprived Arabidopsis, particularly AtPAP26-CW1 and –CW2, as well as AtPAP17, and AtPAP25. Overall, these studies are relevant to applied efforts to bioengineer crops that are more efficient at acquiring and using Pi, urgently needed to reduce the massive overuse of non-renewable and polluting Pi-containing fertilizers in agriculture.
11:30-12:30 BioSci Rm. 3110