Chair & Professor



Areas of Interest

Plant Molecular and Cellular Biology, Functional Genomics, Biotechnology

My lab's research emphasizes two general areas: 1) basic research exploring the function of plant cells at the molecular level; and 2) the application of plant biotechnology to solve practical problems faced by local agriculture. In the first area, we are elucidating the intriguing molecular mechanisms that regulate plant productivity, nutrient transport, protein synthesis and protein folding. We use a combination of molecular, cellular, biochemical and genetic approaches applied to the genetically amenable model plant, Arabidopsis thaliana. We have identified a potassium channel required for the uptake of potassium by plant cells and for providing tolerance to salinity and heavy metal stress. The channel protein is regulated by calmodulin and is a member of the CNGC (cyclic nucleotide gated channel) family. Complementation of E. coli and yeast channel mutants and expression in HEK cells have aided the functional identification and biochemical analysis. We have used a CNGC-specific antiserum, electron microscopy and immunolabeling to localize the channel to the plasma membrane of leaf and root cells. Reverse genetics are being used to identify the phenotypes of channel knockouts. We are also studying protein synthesis and folding in the endoplasmic reticulum (ER) mediated by a class of enzymes designated protein disulfide isomerases (PDI). We have localized these enzymes to the ER, vacuole, chloroplast, golgi and apoplasm. We have identified interacting partners using the yeast two-hybrid system. The green fluorescent protein fused to PDIs combined with PDI-antisera are being used for sub-cellular localization. Protein folding plays an ultimate role in the accumulation of proteins in seeds, the nutritional value of grain, and the trafficking of proteins to other compartments in plants.

In the second area, our primary goals are to decrease the use of pesticides in agriculture and to develop new products (vaccines, medicines) using plants as production systems. We contribute the tools of molecular biology in collaborative research that uses biotechnology to improve anthuriums, papaya, and pineapple. We investigate the genetic manipulation of aging and senescence in Anthuriums, the molecular response to pathogen attack in pineapple and papaya, and the biochemistry of protease inhibitors from pineapple. Human vaccine proteins are being expressed in sugarcane in a manner that prevents the vaccine gene form entering the pollen. A genomics approach is being used to isolate and characterize comprehensive sets of tissue-specific genes from tropical fruit crops. Detailed expression and regulation analyses and tissue-specific promoter isolation are being undertaken.

Our lab also sponsors the Advances in Bioscience Education (ABE) workshop funded by the National Science Foundation grant. This summer program brings community college faculty and students together to gain hands-on experience in real biology research. They work as teams on experimental problems using state-of-the-art molecular biological, bioinformatic, cellular, genomic and biochemical approaches. More information can be found at:


Other Service Projects

Recent Book Chapters and Magazine Articles

D.A. Christopher, 2003. Photosensory Pathways Regulating Chloroplast Gene Expression", (In: Handbook of Photochemistry & Photobiology, M.S.A. Abdel-Mottaleb & H.S. Nalwa, eds), American Scientific Publishers. Vol. 4, Chapter 8, pp.249-268..

D. A. Christopher, 2000 (January). "Engineering Genes: The Gene Genie's Progeny" THE WORLD & I Magazine, Washington Times Press, pp. 172-179.

Recent Journal Publications

Neuteboom LW, Matsumoto KO, Christopher DA,  2009. An extended AE-rich N-terminal trunk in secreted pineapple cystatin enhances inhibition of fruit bromelain and is post-translationally removed during ripening. Plant Physiology 151: 515-527  (Cover Feature)

Porter BW, Zhu YJ, Christopher DA, 2009. Carica papaya genes regulated by Phytophthora palmivora: A new system for comparative genomics. Tropical Plant Biology 2: 84–97.

Porter BW, Zhu YJ, Webb DT, Christopher DA, 2009.  Novel thigmomorphogenetic responses in Carica papaya: Touch decreases anthocyanin levels and stimulates petiole cork outgrowths. Annals of Botany, 103: 847-858.

Ondzighi CA, Christopher DA, Cho EJ, Chang SC, Staehelin LA,  2008.  Arabidopsis Protein Disulfide Isomerase-5 Inhibits Cysteine Proteases during Trafficking to Vacuoles before Programmed Cell Death of the Endothelium in Developing Seeds. The Plant Cell, 20: 2205-2220

Lu D-P, Christopher DA,  2008. Light enhances the unfolded protein response as measured by BiP2 gene expression and the secretory GFP-2SC marker in Arabidopsis. Physiologia Plantarum, 134: 360–368.

Lu, D-P,  Christopher,  DA,  2008. Endoplasmic reticulum stress activates the expression of a sub-group of protein disulfide isomerase genes and AtbZIP60 modulates the response in Arabidopsis thaliana. Molecular Genetics & Genomics. 280:199-210.

Lu, D.-P.,  Christopher,  D.A.   2008.  The effect of irradiance and redox-modifying reagents on the 52  kDa protein disulfide isomerase of Arabidopsis chloroplasts. Biologia Plantarum 52: 42-48.

Guo, KM, Babourina O, Christopher DA, Borsics T, Rengel Z, 2008. The cyclic nucleotide-gated channel, AtCNGC10, influences salt tolerance in ArabidopsisPhysiologia Plantarum 134:499-507.

Porter BW, Aizawa KS, Zhu YJ, Christopher DA, 2008. Differentially expressed and new non-protein-coding genes from a Carica papaya root transcriptome survey. Plant Science, 174:38-50.

Ming, R et al. 2008. Genome of the transgenic tropical fruit tree papaya (Carica papaya L.) Nature 452: 991-995.

Christopher DA, Borsics T, Yuen CYL, Ullmer W, Andème-Ondzighi C, Andres ML, Kang BH, Staehelin L.A. The cyclic nucleotide-gated cation channel AtCNGC10 traffics from the ER via Golgi vesicles to the plasma membrane of Arabidopsis root and leaf cells. Biomedical Central Plant Biology 7(48): 1471-2229.

Borsics T, Webb D, Ondzighi C, Staehelin LA, and Christopher DA, 2007. The cyclic nucleotide-gated calmodulin-binding channel AtCNGC10 localizes to the plasma membrane and influences numerous growth responses and starch accumulation in Arabidopsis thaliana, Planta, 225: 563-573.

Lu DP and Christopher DA, 2006. Immunolocalization of a protein disulfide isomerase to Arabidopsis thaliana chloroplasts and its association with starch biogenesis, International Journal of Plant Science, 167(1): 1-9.

Lau TSL, Eno E, Goldstein G, Smith C, and Christopher DA, 2006. Ambient levels of UV-B in Hawaii combined with nutrient deficiency decrease photosynthesis in near-isogenic maize lines varying in leaf flavonoids: Flavonoids decrease photoinhibition in plants exposed to UV-B, Photosynthetica, 44: 394-403.

Lu DP and Christopher DA, 2005. Analysis of isoforms of protein disulfide isomerase in plants by immuno-microscopy. Microscopy & Microanalysis, 11:1160-1161.

Li XL, Borsics T, Harrington HM, and Christopher DA, 2005. Arabidopsis AtCNGC10 rescues potassium channel mutants of E. coli, yeast and Arabidopsis and is regulated by calcium/calmodulin and cyclic GMP in E. coli. Functional Plant Biology, 32:643 -653.

Hayden, DM and Christopher DA, 2004. Characterization of senescence-associated gene expression and senescence-dependent and -independent cysteine proteases differing in microsomal processing in Anthurium, Plant Science, 166:779-790.

Zhou L, Chen CC, Ming R, Christopher DA, Paull RP, 2003. Apoplastic invertase and its enhanced expression and post-translational control during papaya fruit maturation and ripening," J. Amer. Soc. Hort. Sci. 128:628-635.

Meiri E, Levitan A, Guo F, Christopher DA, Zurd J-P, Danon A, 2002. Characterization of three PDI-like genes in Physcomitrella patens and construction of knock-out mutants, Molecular Genetics & Genomics 267: 231-240.

Neuteboom LW, Kunimitsu WY, Webb D, Christopher DA, 2002. Characterization and tissue-regulated expression of genes involved in pineapple (Ananascomosus L.) root development. Plant Science, 165:1021-1035.

Shen Y, Danon A and Christopher DA, 2001. RNA binding-proteins interact specifically with the Arabidopsis chloroplast psbA mRNA 5' untranslated region in a redox-dependent manner, Plant & Cell Physiology 42:1071-1078.

Thum KE, Kim M, Christopher DA, and Mullet JE 2001. Cryptochrome 1, cryptochrome 2 and phytochrome A co-activate the chloroplast psbD blue light-responsive promoter, The Plant Cell 13: 2747-2760.

Chun L, Kawakami A, and Christopher DA, 2001. Phytochrome A mediates blue light and UV-A-dependent chloroplast gene transcription in green leaves, Plant Physiology 125:1957-1966.

Zhou L, Christopher DA, and Paull RE, 2000. Defoliation and fruit removal of papaya (Carica papaya C.): Fruit production, sugar accumulation and sucrose metabolism. J. American Society Horticultural Science 125: 644-652 .

Christopher DA, Shen Y, Dudley P, Tsinoremas NF, 1999. Expression of a higher plant chloroplast psbD promoter in a cyanobacterium (Synechococcus sp. strain PCC7942) reveals a conserved cis-element, designated PGT, that differentially interacts with sequence-specific binding factors during leaf development. Current Genetics, 35:657-666.

Kim M, Christopher DA, Mullet J, 1999. ADP-dependent phosphorylation regulates association of a DNA-binding complex with the barley chloroplasts psbD blue-light-responsive promoter. Plant Physiology 119: 663-670.

Tsinoremas NF, Kawakami A, Christopher DA, 1999. High-fluence blue light stimulates transcription from a higher plant chloroplast psbA promoter expressed in a cyanobacterium, Synechococcus (sp. strain PCC7942) Plant & Cell Physiology. 40:448-452.

Christopher DA. and Hoffer PH, 1998. DET1 represses a chloroplast blue light-responsive promoter in a developmental and tissue-specific manner in Arabidopsis thaliana. The Plant Journal 14:1-11.

Hoffer PH and Christopher DA, 1997. Structure and blue light-responsive transcription of a chloroplast psbD promoter from Arabidopsis thaliana. Plant Physiology 115: 213 - 22

Christopher DA, Li X, Kim M, Mullet JE, 1997. Involvement of protein kinase and extra-plastidic serine/threonine protein phosphatases in signaling pathways regulating plastid transcription and the psbD blue light-responsive promoter in barley (Hordeum vulgare L.). Plant Physiology 113: 1273-1282.

Christopher DA 1996 Leaf development and phytochrome modulate the activation of psbD-psbC transcription by high-fluence blue light in barley chloroplasts. Photosynthesis Research 47: 239-251.

Publications prior to 1996