Purple acid phosphatase 12: a tool to study the phosphate starvation response in Arabidopsis thaliana

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Title: Purple acid phosphatase 12: a tool to study the phosphate starvation response in Arabidopsis thaliana
Author: Patel, Ketan
Abstract: Phosphorus is an essential element for plant growth and development . Due to its low availability , solubility and mobility , phosphate is often the limiting macronutrient for crops and other plants . Plants have evolved several responses to phosphate deficiency . However , very little is known about the molecular basis of these responses . Here , I study the expression of PAP12 , its role in the phosphate starvation response and the interaction of its promoter with nuclear factors . Analysis of a PAP12 T -DNA insertion line (pap12 -1 ) revealed PAP12 is responsible for the majority of the acid phosphatase activity detected by the standard in -gel assay . RNA gel blots showed that PAP12 was induced only by Pi deficiency , and not by general nutrient stress . PAP12 expression , at the RNA and protein level , reflected endogenous phosphate levels in two mutants with altered phosphate accumulation . In the pho1 mutant , PAP12 expression and activity were up -regulated with respect to wild -type plants , and in the pho2 mutant , PAP12 expression and activity were reduced . Analysis of the PAP12 promoter using promoter -GUS fusions revealed expression in leaves , roots , flowers , hydathodes , root tips , and pollen grains . This broad pattern of expression suggests that PAP12 functions throughout the plant in response to low phosphate concentrations . The results showed PAP12 does not play a major role in phosphate remobilization , acquisition or in helping plants cope with low phosphate environments . Instead , the major phenotype associated with PAP12 deficiency was a significant delay in flowering in the low -phosphate pho1 background and a slight acceleration of flowering in the high -phosphate pho2 background over -expressing PAP12 . These results suggest that PAP12 may have a role in linking phosphate status with the transition to flowering . Finally , I used promoter deletion and DNA -protein interaction assay to understand PAP12 expression upon phosphate starvation . A 35 -bp region of the PAP12 promoter was identified as an important phosphate regulatory cis -element required for induction during phosphate starvation . We isolated a 23 .5 kDa nuclear factor , which binds to this 35 -bp region of the PAP12 promoter in a phosphate -dependent manner . The work presented here will add to our knowledge about the molecular processes that regulate phosphate nutrition .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -1044
Date: 2009-05-15

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Purple acid phosphatase 12: a tool to study the phosphate starvation response in Arabidopsis thaliana. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -1044 .

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