The Harper lab is interested in how a plant can use as few as 28,000 genes to develop and survive under extreme environmental conditions, such as cold, heat, drought and salt stress. A primary focus is on calcium signaling. The lab employs genetic, cell, bioinformatic, and biochemical approaches, using Arabidopsis and yeast as model systems.

Specific aims are focused on questions of enzyme structure and function for members of the following three gene families.

• Calcium Dependent Protein Kinases (CDPKs). CDPKs have a unique structure defined by the presence of a calmodulin-like regulatory domain fused to the C-terminal end of the kinase. They are only found in plants and some protist, including the human parasite Plasmodium, the causative agent of malaria.
   
• Cyclic Nucleotide Gated Channels (CNGCs). These ion channels have been implicated in calcium signaling and are regulated by both cyclic nucleotides and calmodulin.
   
• P-type ATPase Ion Pumps. These ion pumps are used to transport across membranes a wide variety of ions, including H+, Ca2+, Na+, and heavy metals. They are involved in ion homeostasis, nutrient acquisition from the soil, toxic ion efflux, and signal transduction.

Schiøtt, M., S. Romanowsky, M. K. Jakobsen, L. Bækgaard, M.G. Palmgren, J.F. Harper. (2004). A plant plasma membrane Ca2+ pump is required for normal pollen tube growth and fertilization. PNAS 101: 9502-9507

Harper J, Breton G, Harmon A (2004) Decoding CA signals through plant protein kinases. Annual Reviews of Plant Biology. 55: 263-88

Hussain,D., M J Haydon, Y Wang, E Wong, S.M. Sherson, J. Young, J. Camakaris, JF. Harper, C. S. Cobbett ( 2004). P-type ATPase heavy metal transporters with roles in essential zinc metabolism in Arabidopsis. Plant Cell 16: 1327-1339

Lahner B, Gong J, Mahmoudian M, Smith EL, Abid KB, Rogers EE, Guerinot ML, Harper JF, Ward JM, McIntyre L, Schroeder JI, Salt DE. (2003) Genomic scale profiling of nutrient and trace elements in Arabidopsis thaliana. Nat Biotechnol. 21(10): 1215-1221

Sanders D, Pelloux J, Brownlee C, Harper JF (2002) Calcium at the Crossroads of Signaling. The Plant Cell. Supplement 2002: S401-S417

Wu Z, Liang F, Hong B, Young JC, Sussman MR, Harper JF and Sze H (2002) An ER-bound Ca2+/Mn2+ pump, ECA1, supports plant growth and confers tolerance to Mn2+ stress. Plant Physiol 130:128-37

Christodoulou J, Hu H, Chung, J, Rance M, Harper JF, Chazin WJ (2002) "1H, 15N and 13C assignments of the regulatory domains of calcium-dependent protein kinase (CDPK)." J Biomolec. NMR 23: 249-50

Veeraraghavan S, Fagan P A, Hu H, Lee V, Harper JF, Huang B, Chazin WJ (2002) Structural independence of the two EF-hand domains of caltractin. J Biol Chem 28: 28564-71