|Norelli, John (jay)|
Submitted to: International Horticultural Congress
Publication Type: Abstract Only
Publication Acceptance Date: April 10, 2010
Publication Date: August 27, 2010
Citation: Wisniewski, M.E., Norelli, J.L., Bassett, C.L., Macarisin, D., Artlip, T.S., Dardick, C.D. 2010. Overexpression of a peach (Prunus persica) AP2/ERF-family transcription factor in apple (Malus x domestica) induces growth cessation in response to short photoperiod [abstract]. International Horticultural Congress. p. 246. Technical Abstract: Climate change will result in extreme swings in temperature during late fall and early spring that will have a negative impact on woody plants. Apple may be especially sensitive to the predicted weather patterns since growth cessation is regulated by low temperature rather than daylength. We have identified several short-day and low-temperature regulated genes in both peach and apple including several AP2/ERF – family transcription factors and have taken a transgenic approach to understand gene function. Currently, we report on the molecular and phenotypic analysis of several lines of transgenic apple (M26) that constitutively overexpress a specific AP2/ERF transcription factor gene (PpSD1) obtained from a cDNA library constructed from 'Loring' peach bark tissues harvested in December. At least five transgenic lines were identified, and three of these were propagated and subjected to molecular and phenotypic analyses. Phenotypic analysis indicated that, compared to untransformed plants, the transgenic lines varied in levels of cold hardiness and their response to short photoperiod (8 h day:16 h night). Molecular analysis indicated that the level of phenotypic change was associated with the level of expression of PpSD1. The highest expressing line exhibited several degrees of improved cold hardiness in both the non-acclimated and acclimated state. Most remarkably, the transgenic apple lines exhibited photoperiod-induced cessation of growth. Transgenic lines of apple placed under short day conditions for one to four weeks and then returned to optimum growth conditions in the greenhouse did not resume growth but rather set terminal buds and the leaves began to senesce. The rapidity of dormancy induction increased with the length of SD exposure. In contrast, while growth slowed under SD conditions in untransformed 'M26'apple plants, normal growth resumed once plants were returned to optimum growth conditions. This is the first report of photoperiod-induced growth cessation in apple.