Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 26, 2003
Publication Date: July 26, 2003
Citation: Liu, J., Samac, D.A., Allan, D., Vance, C.P. 2003. Regulation of phosphate deficiency induced genes in nitrogen fixing nodules and in reproductive tissues of transgenic alfalfa [abstract]. American Society of Plant Biologists Annual Meeting. Available: http://Z126.96.36.199/pb2003/public/P39/0210.html. Technical Abstract: Phosphorus (P) is an essential macronutrient for plant growth and development. Under P deficiency, genes with various functions in P uptake, mobilization, and metabolism are activated to cope with biochemical and metabolic changes. In general, high affinity phosphate (Pi) transporters are considered crucial in the enhanced Pi uptake when the external Pi concentration is extremely low. In comparison, low affinity phosphate transporters are involved in subsequent remobilization within plant. We have characterized a phosphate transporter gene, LaPT1, from white lupin, Lupinus albus, and demonstrated enhanced accumulation of mRNA in response to Pi deficiency. By analyzing the activity of a LaPT1 promoter:GUS reporter gene in transgenic alfalfa, we found that LaPT1 promoter is not only activated by Pi deficiency in roots but also in nitrogen-fixing nodules. In contrast, no induced promoter activity has been observed in ineffective nodules, i.e., nodules formed when alfalfa plants are inoculated with a nif - Rhizobium mutant strain. The correlation between the induced LaPT1 promoter activity and symbiotic nitrogen fixation not only confirms previous studies that plants with symbiotic nitrogen fixation have higher requirement for P but also provides new evidence that plants seem to distinguish the need of P for nodule development and nodule function. In developing seeds LaPT1 promoter is specifically active in hilum. During seed germination, LaPT1 gene is rapidly activated in both cotyledons and radicles. The cellular pattern of LaPT1:GUS activity in seeds indicates that internal mobilization of Pi is strictly regulated and LaPT1 is probably involved in nutrient import into developing seeds and remobilization in germinated seeds.