Identification of genes associated with growth cessation and bud dormancy entrance using a dormancy-incapable tree mutant

Abstract

BackgroundIn many tree species the perception of short days (SD) can trigger growth cessation, dormancy entrance, and the establishment of a chilling requirement for bud break. The molecular mechanisms connecting photoperiod perception, growth cessation and dormancy entrance in perennials are not clearly understood. The peach [Prunus persica (L.) Batsch] evergrowing (evg) mutant fails to cease growth and therefore cannot enter dormancy under SD. We used the evg mutant to filter gene expression associated with growth cessation after exposure to SD. Wild-type and evg plants were grown under controlled conditions of long days (16 h/8 h) followed by transfer to SD (8 h/16 h) for eight weeks. Apical tissues were sampled at zero, one, two, four, and eight weeks of SD and suppression subtractive hybridization was performed between genotypes at the same time points.ResultsWe identified 23 up-regulated genes in the wild-type with respect to the mutant during SD exposure. We used quantitative real-time PCR to verify the expression of the differentially expressed genes in wild-type tissues following the transition to SD treatment. Three general expression patterns were evident: one group of genes decreased at the time of growth cessation (after 2 weeks in SD), another that increased immediately after the SD exposure and then remained steady, and another that increased throughout SD exposure.ConclusionsThe use of the dormancy-incapable mutant evg has allowed us to reduce the number of genes typically detected by differential display techniques for SD experiments. These genes are candidates for involvement in the signalling pathway leading from photoperiod perception to growth cessation and dormancy entrance and will be the target of future investigations.

Molecular aspects of dormancy in peach (Prunus persica [L.] Batsch.)

“…These observations are in agreement with recent findings by Jiménez et al (2010a), showing that genes encoding a LEA and KEEP ON GOING (KEG)-like proteins are misregulated in evg mutant during short day induction of bud dormancy. KEG is an E3 ligase which regulates ABI5 abundance by means of its ubiquitination and subsequent proteasome-mediated degradation in A. thaliana (Stone et al, 2006).…”

“…Such ESTs and other related to plant dormancy for the first time in this work provide insight into the signals and processes regulating bud dormancy in general, and offer a series of gene sequences susceptible to be used for marker-assisted selection in peach breeding. DAM1 and DAM6 are up-regulated during bud growth cessation, following a change from long to short day photoperiod (Jiménez et al, 2010a), and down-regulated during dormancy release in two different peach cultivars (Leida et al, 2010). In a recent work, the expression of DAM5 and DAM6…”

“…In peach, a 60 kDa dehydrin was found at a lower concentration in the evg mutant when compared with coldacclimated standard deciduous trees . Numerous late embryogenesis abundant (LEA) proteins have been identified in different studies in a wide range of tissues (Horvath et al, 2003;Mazzitelli et al, 2007;Schrader et al, 2004; Basset et al, 2006;Jiménez et al, 2010a). Although the function of LEA proteins is not well known at the molecular level, they are supposed to have a role in protecting cells from desiccation and temperature stress.…”

“…From the six DAM genes, we chose DAM6 for subsequent expression analysis due to its recurrent identification in peach-dormancy genomic approaches (Jiménez et al, 2010a;Leida et al, 2010), and a close correlation of its expression with dormancy release and bud break found by Jiménez et al (2010b), Yamane et al (2011), and in this work. We measured DAM6 expression in two representative cultivars of early ('Red Candem') and relatively late ('Big Top') cultivars at different dates during bud dormancy release.…”

“…Previous studies employed the SSH procedure for the isolation of bud dormancy-related genes in peach. Jiménez et al (2010a) used SSH to compare wild type and evg mutant gene expression after bud growth cessation mediated by transfer to short day conditions. From 23 genes found by Jiménez and coworkers, only one (DAM6) has been also obtained in this work, most likely due to differences in the experimental design.…”