Abstract
Phosphate deficiency is wide spread in the nature. The deficiency results in several morphological and biochemical changes in plants. Some of these changes have been shown to involve altered gene expression. We have isolated two full--length cDNAs (AtPT1 and AtPT2), showing significant amino acid sequence similarity with the high-affinity phosphate transporters of yeast, Neurospora and the mycorrhizal fungi Glomus versiforme, from a phosphate-starved Arabidopsis root library. The transcripts of both genes are highly induced under Pi starvation and they are expressed in roots. Using Arabidopsis cDNAs as probes, we have isolated several tomato root cDNA clones representing the two different genes. The expression characteristics of the tomato isoforms of the putative high affinity phosphate transporter genes will be discussed. The northern blots of RNA isolated from phosphate-deficient and phosphate-sufficient roots of tomato indicated that both genes are strongly induced in response to Pi starvation in roots. Furthermore, by the method of differential display of mRNA, we have cloned and characterized a full-length cDNA representing a Pi starvation induced gene (TPSI1) from tomato. The gene is expressed as a specific response to Pi starvation in roots and leaves. The TPSI1 is an intron-less gene represented by a single copy in the tomato genome. The structure, expression, and functional significance of these genes will be discussed. This research has been supported, in part, by USDA grant 94-37100-0834 to KGR.
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