Title: Over-expression of SOD in young apple trees enhances abiotic stress resistance Authors
Submitted to: Plant and Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: October 31, 2007
Publication Date: January 10, 2008
Citation: Artlip, T.S., Wisniewski, M.E. 2008. Over-expression of SOD in young apple trees enhances abiotic stress resistance. Plant and Animal Genome Conference. San Diego, CA. Book of Abstracts. Vol. 16, Pg. 234. Technical Abstract: Reactive oxygen intermediates (ROIs) are induced during both biotic and abiotic stress, either as signaling molecules or as a response to stress injury. ROIs are highly destructive to cell components, and the injury resulting from these compounds is referred to as oxidative stress. Antioxidant enzymes, such as superoxide dismutase (SOD), scavenge oxygen radicals preventing the injury resulting from oxidative stress. The objective of the present research was to produce transgenic apple plants (Malus x domestica 'Royal Gala') with enhanced production of a cytosolic SOD. A full-length SOD cDNA was isolated from spinach by a combination of RT-PCR and conventional plaque lift screening of a spinach cDNA library. The SOD gene was mobilized into the binary vector pCGN 1578 (a combination of pCGN 1532 and pRTL2) for Agrobacterium-mediated transformation of apple. The resulting un-transformed, SOD-over-expression (SOD-OX), and blank-cassette lines were evaluated for resistance to abiotic stresses, including high temperature, chilling, and freezing injury, by ion leakage assays of leaves and bark from one-year-old trees. Results indicated that SOD-OX leaves exhibited improved resistance to both acute and longer-term exposure to elevated temperatures compared to the non SOD-OX lines. Cold tolerance of non-acclimated SOD-OX tissues did not differ from the control plants. Cold acclimated (two weeks exposure to a short day photoperiod) leaves and bark of SOD-OX trees had more cold tolerance compared to the other lines. Whether transgenic SOD-OX trees would have increased resistance to ROI-mediated disorders, such as sunscald or sunburn on apples, needs to be determined.