Abstract
Bud dormancy is an adaptive process that allows trees to survive the hard environmental conditions that they experience during the winter of temperate climates. Dormancy is characterized by the reduction in meristematic activity and the absence of visible growth. A prolonged exposure to cold temperatures is required to allow the bud resuming growth in response to warm temperatures. In fruit tree species, the dormancy cycle is believed to be regulated by a group of genes encoding MADS-box transcription factors. These genes are called DORMANCY-ASSOCIATED MADS-BOX (DAM) and are phylogenetically related to the Arabidopsis thaliana floral regulators SHORT VEGETATIVE PHASE (SVP) and AGAMOUS-LIKE 24. The interest in DAM and other orthologs of SVP (SVP-like) genes has notably increased due to the publication of several reports suggesting their role in the control of bud dormancy in numerous fruit species, including apple, pear, peach, Japanese apricot, and kiwifruit among others. In this review, we briefly describe the physiological bases of the dormancy cycle and how it is genetically regulated, with a particular emphasis on DAM and SVP-like genes. We also provide a detailed report of the most recent advances about the transcriptional regulation of these genes by seasonal cues, epigenetics and plant hormones. From this information, we propose a tentative classification of DAM and SVP-like genes based on their seasonal pattern of expression. Furthermore, we discuss the potential biological role of DAM and SVP-like genes in bud dormancy in antagonizing the function of FLOWERING LOCUS T-like genes. Finally, we draw a global picture of the possible role of DAM and SVP-like genes in the bud dormancy cycle and propose a model that integrates these genes in a molecular network of dormancy cycle regulation in temperate fruit trees.
Highlights
Reviewed by: David Horvath, United States Department of Agriculture, United States Hisayo Yamane, Kyoto University, Japan Erika Varkonyi-Gasic, The New Zealand Institute for Plant & Food Research Ltd., New Zealand
These genes are called DORMANCY-ASSOCIATED MADS-BOX (DAM) and are phylogenetically related to the Arabidopsis thaliana floral regulators SHORT VEGETATIVE PHASE (SVP) and AGAMOUS-LIKE 24
We briefly describe the physiological bases of the dormancy cycle and how it is genetically regulated, with a particular emphasis on DAM and SVP-like genes
Summary
Temperate trees are distributed over a geographical zone of the globe that spans between the tropics and the polar regions. We clustered the expression patterns of DAM genes from several species (i.e., apple, Japanese pear, Japanese apricot, peach, sweet cherry, Chinese cherry, leafy spurge and kiwifruit) into three different groups based on their seasonal pattern of expression during the growth and dormancy cycle (Figure 3). We excluded DAM and SVP-like genes from poplar (Howe et al, 2015) and tea plant (Hao et al, 2017), as their seasonal expression pattern did not fit in any of the proposed groups Whether this indicates that these genes are not involved in dormancy cycle or have a different role in poplar and tea plant remains uncertain. The expression pattern #2 was identified for DAM genes of Japanese apricot (Sasaki et al, 2011; Zhao et al, 2018a,b), peach (Li et al, 2009; Jiménez et al, 2010b; Yamane et al, 2011a,b,c), Japanese pear (Ubi et al, 2010; Liu et al, 2012; Bai et al, 2013; Saito et al, 2013; Ito et al, 2016; Niu et al, 2016), apple (Falavigna et al, 2014; Mimida et al, 2015; Wisniewski et al, 2015; Kumar et al, 2016, 2017; Porto et al, 2016; Wu et al, 2017a), sweet and Chinese cherry (Zhu et al, 2015; Rothkegel et al, 2017),
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