|Norelli, John (jay)|
|Gasic, Ksenija - UNIV OF ILLINOIS|
|Korban, Schulyer - UNIV OF ILLINOIS|
Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: March 19, 2007
Publication Date: July 16, 2007
Citation: Wisniewski, M.E., Bassett, C.L., Norelli, J.L., Macarisin, D., Artlip, T.S., Gasic, K., Korban, S. 2007. Expressed-sequence tag (EST) analysis of the response of apple (Malus x domestica) to low temperature and water deficit. HortScience. 42:993. Technical Abstract: Apple leaf, bark, xylem, and root tissues were used to make cDNA libraries from non-stressed (control) trees and trees exposed to either low-temperature (5 C for 24 h) or water deficit (45% of saturated pot mass for 2 weeks). Over 22,600 clones from the nine libraries were subjected to 5' single pass sequencing, clustered, and annotated. BlastX analysis indicated that within the libraries, 65-72% of the clones had a high similarity to known function genes, 6-15% had no functional assignment, and 15-26% were completely novel. The ESTs were combined into three classes (control, low-temperature, water deficit), and the annotated genes in each class were placed into one of ten different functional categories. Results indicated a down regulation of genes involved in general metabolism and photosynthesis, while a significant increase in defense/stress-related genes, protein metabolism, and energy was observed. In particular, there was a three-fold increase in the number of stress genes observed in the water deficit libraries. The number of stress genes in response to low temperature, although elevated, was much less, reflecting the shorter (24h) exposure to stress. More specifically, genes that code for the following proteins were overexpressed in the low-temperature libraries: dehydrin and metallothionein-like proteins, ubiquitin proteins, a dormancy-associated protein, a plasma membrane intrinsic protein, and an RNA-binding protein. Genes that were up-regulated in the water deficit libraries fell mainly into the functional categories of stress (heat shock proteins, dehydrins) and photosynthesis. With few exceptions, the overall differences in down-regulated genes was nominal compared to differences in up-regulated genes. The results of this apple study are similar to other global studies of plant response to stress.