@article{densiow_rueschhoff_daub_2007, title={Regulation of the Arabidopsis thaliana vitamin B-6 biosynthesis genes by abiotic stress}, volume={45}, ISSN={["0981-9428"]}, DOI={10.1016/j.plaphy.2007.01.007}, abstractNote={Vitamin B6 (pyridoxine and its vitamers) plays an essential role as a co-factor for enzymatic reactions and has also recently been implicated in defense against cellular oxidative stress. The biosynthetic pathway was thoroughly characterized in Escherichia coli, however most organisms, including plants, utilize an alternate pathway involving two genes, PDX1 and PDX2. Arabidopsis thaliana contains one copy of PDX2, but three full-length copies of PDX1, one each on chromosomes 2, 3, and 5 (referred to as PDX1.1, PDX1.2, and PDX1.3, respectively). Phylogenetic analysis of the PDX1 homologues in A. thaliana showed that PDX1.1 and PDX1.3 clustered with the homologues from the other dicots, whereas PDX1.2 was more divergent, and did not cluster with either the dicots or monocots. Expression analysis using quantitative PCR showed that PDX1.1 and PDX1.3 were highly expressed in A. thaliana rosettes, while PDX1.2 showed only low level expression. All three PDX1 genes and PDX2 were responsive to abiotic stressors including high light, chilling, drought, and ozone, however, the response of PDX1.2 was disparate from that of the other PDX genes, showing a lessened response to high light, chilling, and drought, but an increased response to ozone. Green fluorescent protein fusion studies demonstrated that PDX2 localizes in the nucleus and membranes of cells, consistent with recent published data for PDX1. Insight into regulation of the biosynthetic genes during abiotic stress could have important applications in the development of stress-tolerant crops.}, number={2}, journal={PLANT PHYSIOLOGY AND BIOCHEMISTRY}, author={Densiow, Sheri A. and Rueschhoff, Elizabeth E. and Daub, Margaret E.}, year={2007}, month={Feb}, pages={152–161} }
 @article{denslow_walls_daub_2005, title={Regulation of biosynthetic genes and antioxidant properties of vitamin B-6 vitamers during plant defense responses}, volume={66}, ISSN={["0885-5765"]}, DOI={10.1016/j.pmpp.2005.09.004}, abstractNote={Vitamin B6, an essential cofactor in enzymatic reactions, has only recently been linked to cellular oxidative stress. We investigated the role of this vitamin as an antioxidant in oxidative responses linked to plant defense. B6 vitamers effectively quenched superoxide and had antioxidant activity when assayed in vitro. The de novo B6 biosynthetic genes (PDX1 and PDX2) were identified in Nicotiana tabacum cv. ‘Burley 21’ and their transcript abundance was assayed during defense responses. PDX1 and PDX2 transcript levels decreased following inoculation with the incompatible pathogen Pseudomonas syringae pv. phaseolicola and transiently increased in response to salicylic acid and methyl jasmonate. Excess vitamin B6 in tobacco leaves interfered with the development of a hypersensitive response caused by P. syringae pv. phaseolicola and increased disease severity caused by the compatible bacterium P. syringae pv. tabaci. Our findings indicate that during plant defense responses, vitamin B6 functions and its synthesis is regulated in a manner consistent with this vitamin's activity as an antioxidant and modulator of active oxygen species in vivo.}, number={6}, journal={PHYSIOLOGICAL AND MOLECULAR PLANT PATHOLOGY}, author={Denslow, SA and Walls, AA and Daub, ME}, year={2005}, month={Jun}, pages={244–255} }
 @article{wetzel_ehrenshaft_denslow_daub_2004, title={Functional complementation between the PDX1 vitamin B-6 biosynthetic gene of Cercospora nicotianae and pdxJ of Escherichia coli}, volume={564}, ISSN={["1873-3468"]}, DOI={10.1016/S0014-5793(04)00329-1}, abstractNote={The pathway for de novo vitamin B 6 biosynthesis has been characterized in Escherichia coli , however plants, fungi, archaebacteria, and most bacteria utilize an alternative pathway. Two unique genes of the alternative pathway, PDX1 and PDX2 , have been described. PDX2 encodes a glutaminase, however the enzymatic function of the product encoded by PDX1 is not known. We conducted reciprocal transformation experiments to determine if there was functional homology between the E. coli pdxA and pdxJ genes and PDX1 of Cercospora nicotianae . Although expression of pdxJ and pdxA in C. nicotianae pdx1 mutants, either separately or together, failed to complement the pyridoxine mutation in this fungus, expression of PDX1 restored pyridoxine prototrophy to the E. coli pdxJ mutant. Expression of PDX1 in the E. coli pdxA mutant restored very limited ability to grow on medium lacking pyridoxine. We conclude that the PDX1 gene of the alternative B 6 pathway encodes a protein responsible for synthesis of the pyridoxine ring.}, number={1-2}, journal={FEBS LETTERS}, author={Wetzel, DK and Ehrenshaft, M and Denslow, SA and Daub, ME}, year={2004}, month={Apr}, pages={143–146} }