Differences in Cold Hardiness and Dehydrin Gene Expressions in Response to Artificial Deacclimation and Reacclimation in Peach (Prunus persica)

Changes of cold hardiness were estimated in the shoots of two peach (Prunus perisica) cultivars ‘Daewol’ and ‘Kiraranokiwami’ to mimic unseasonable changes of temperatures that occur in late winter and/or early spring through repeated deacclimation and reacclimation treatments. In addition, changes of dehydrin gene expressions by quantitative real-time PCR were examined to find out the relationship with cold hardiness. Patterns of cold hardiness declined dramatically during the deacclimation and rose during the reacclimation in both cultivars. Our results indicated that ‘Daewol’, which was more cold-tolerant in previous studies, possessed higher capacity in response to the repeated deacclimation and reacclimation treatments. Our result indicates that recent repeated warm spell may cause premature deacclimation in late winter and early spring. Changes of dehydrin gene expressions (PpDhn1, PpDhn2, and PpDhn3) were positively correlated with changes of cold hardiness throughout the whole experiment. PpDhn1, whose promoter contains paired ABA responsive elements (ABREs) and two C-repeat/dehydration responsive elements (CRT/DREs) that are related with cold/dehydration response, showed dramatic decreases in deacclimation treatments compared to BT in both cultivars and indicated almost similar recoveries in reacclimation treatments. Expression of PpDhn2, which was most responsive to dehydration which may correlate with the presence of paired ABREs near the TATA box, showed gradual decreases in reacclimation treatments compared to BT, indicating repeated down- and up- patterns and was the most highest correlation with fluctuation of cold hardiness in both cultivars (r = -0.77 in ‘Daewol’ and -0.81 in ‘Kiraranokiwami’). PpDhn3 expression levels of ‘Daewol’ were much higher than those of ‘Kiraranokiwami’ in all the treatments, indicating repeated down- and up- patterns.