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Title: DIFFERENTIAL DISTRIBUTION OF THE COGNATE AND HEAT-STRESS INDUCED ISOFORMS OF HIGH MR CIS-TRANS PROLYLPEPTIDYL ISOMERASE (FKBP) IN THE CYTOPLASM AND NUCLEOPLASM

Author
item DWIVEDI, R - HOWARD UNIVERSITY
item BREIMAN, A - TEL AVIV UNIVERSITY
item Herman, Eliot

Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2003
Publication Date: 12/1/2003
Citation: DWIVEDI, R.S., BREIMAN, A., HERMAN, E.M. DIFFERENTIAL DISTRIBUTION OF THE COGNATE AND HEAT-STRESS INDUCED ISOFORMS OF HIGH MR CIS-TRANS PROLYLPEPTIDYL ISOMERASE (FKBP) IN THE CYTOPLASM AND NUCLEOPLASM. JOURNAL OF EXPERIMENTAL BOTANY. 2003. V 54. P. 2679-2689.

Interpretive Summary: The largest factor in loss of crop productivity in the United States is the cumulative effects of various abiotic stresses of temperature extremes and water excess or deficit. Because these stresses are due to weather, they are still outside the control of farmers and industry. One partial solution is to produce more stress-tolerant crops by either breeding or by gene manipulation. In order to undertake these approaches, the underlying biology of stress responses must be elucidated and with this, key markers for breeding, or genes to manipulate become available. In the present manuscript, the biology of a gene that responds to heat stress is described. This protein functions to rotate segments of a protein and may function to repair proteins damaged by thermal stress. The results have shown that this protein concentrates at sites in the cell's DNA and suggest a protective function that is to ensure the continued expression of genes even under highly-stressful conditions. Such results are part of a gene discovery objective as this gene might prove useful for transfer experiments designed to test whether its presence could enhance thermal resistance in other crops. The present results are primarily of interest to scientists. However, should further experiments show that this protein is useful to impede thermal damage, then these results could be of interest to the biotechnology industry as a gene to moderate abiotic stress.

Technical Abstract: Wheat root tips express a 73 kD cognate and 77 kD heat-shock-induced isoforms of peptidyl prolyl cis-trans isomerase (FK506 binding protein; FKBP) that are part of a large chaperone complex with hsp90. The 73 kD and 77 kD FKBPs have very similar sequences, differing primarily in the N- and C-terminal 20 amino acids. To define their potential functional roles, the 73 kD and 77 kD FKBPs were localized in root tips using antigen-affinity purified antibodies. The cognate 73 kD FKBP is localized in the cytoplasm and appears enriched around the periphery of the early vacuoles and vesicles exiting the trans-Golgi. Parallel assays with antibodies directed against tonoplast aquaporin confirmed the association of FKBP with an early vacuole compartment. Sucrose-gradient-centrifugation analysis of root tip lysates also showed that 73 kD FKBP is co-fractionated with tonoplast aquaporin and V-ATPase in a light compartment near the top of the gradient. The FKBP remains at the bottom of a flotation gradient indicating that the FKBP complex can be easily removed from membranes. Heat-shock treatment of root tips induces the accumulation of the 77 kD FKBP, while the abundance of 73 kD FKBP remains constant. Quantitative EM immunogold assays of the intracellular distribution of FKBP over an 8-h-heat-shock time course showed that FKBP is initially present in the cytoplasm, but is transported into the nucleus where it accumulates in the nucleoplasm and into specific subnuclear domains.