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Research Paper

Differential expression and phylogenetic analysis suggest specialization of plastid-localized members of the PHT4 phosphate transporter family for photosynthetic and heterotrophic tissues

Biwei Guo, Sonia Irigoyen, Tiffany B. Fowler and Wayne K. Versaw

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Plastids rely on multiple phosphate (Pi) transport activities to support and control a wide range of metabolic processes, including photosynthesis and carbon partitioning. Five of the six members of the PHT4 family of Pi transporters in Arabidopsis thaliana (PHT4;1-PHT4;5) are confirmed or predicted plastid proteins. As a step towards identifying the roles of individual PHT4 Pi transporters in chloroplast and non-photosynthetic plastid Pi dynamics, we used promoter-reporter gene fusions and quantitative RT-PCR studies, respectively, to determine spatial and diurnal gene expression patterns. PHT4;1 and PHT4;4 were both expressed predominantly in photosynthetic tissues, although expression of PHT4;1 was circadian and PHT4;4 was induced by light. PHT4;3 and PHT4;5 were expressed mainly in leaf phloem. PHT4;2 was expressed throughout the root, and exhibited a diurnal pattern with peak transcript levels in the dark. The remaining member of this gene family, PHT4;6, encodes a Golgi-localized protein and was expressed ubiquitously. The overlapping but distinct expression patterns for these genes suggest specialized roles for the encoded transporters in multiple types of differentiated plastids. Phylogenetic analysis revealed conservation of each of the orthologous members of the PHT4 family in Arabidopsis and rice, which is consistent with specialization, and suggests that the individual members of this transporter family diverged prior to the divergence of monocots and dicots.

Authors

Biwei Guo

Department of Biology; Texas A&M University; College Station, Texas USA

Sonia Irigoyen

Department of Biology; Texas A&M University; College Station, Texas USA; Molecular and Environmental Plant Sciences Program; Texas A&M University; College Station, Texas USA

Tiffany B. Fowler

Department of Biology; Texas A&M University; College Station, Texas USA

Wayne K. Versaw

Department of Biology; Texas A&M University; College Station, Texas USA; Molecular and Environmental Plant Sciences Program; Texas A&M University; College Station, Texas USA

This is an open-access article

 Download PDF

If the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.