Budbreak in kiwifruit (Actinidia deliciosa) can be poor in locations that have warm winters with insufficient winter chilling. Kiwifruit vines are often treated with the dormancy-breaking chemical hydrogen cyanamide (HC) to increase and synchronize budbreak. This treatment also offers a tool to understand the processes involved in budbreak. A genomics approach is presented here to increase our understanding of budbreak in kiwifruit. Most genes identified following HC application appear to be associated with responses to stress, but a number of genes appear to be associated with the reactivation of growth. Three patterns of gene expression were identified: Profile 1, an HC-induced transient activation; Profile 2, an HC-induced transient activation followed by a growth-related activation; and Profile 3, HC- and growth-repressed. One group of genes that was rapidly up-regulated in response to HC was the glutathione S-transferase (GST) class of genes, which have been associated with stress and signalling. Previous budbreak studies, in three other species, also report up-regulated GST expression. Phylogenetic analysis of these GSTs showed that they clustered into two sub-clades, suggesting a strong correlation between their expression and budbreak across species.

The DRM1/ARP gene family is increasingly exhibiting associations with stress conditions at the transcript level. Traditionally correlated with dormancy, increases in transcript levels in response to various treatments have also been reported in various species. As alternative transcript splicing is common in stress conditions, the splice variants of AtDRM1 and AtDRM2 were assessed further in this study. A previously undescribed splice variant of AtDRM1 (AtDRM1.6) is introduced in this work. In silico analyses of predicted protein sequence of all splice variants showed that all variants retain the predicted intrinsically disordered nature. Transcriptional studies of AtDRM1 and AtDRM2 in response to a wide range of abiotic, physical and hormonal treatments showed that AtDRM1.6 is differentially regulated at the transcriptional level compared with other splice variants. Promoter analyses demonstrated AtDRM1 light regulation via the upstream promoter sequence.

Plants must carefully regulate their development in order to survive a wide range of conditions. Of particular importance to this is dormancy release, deciding when to grow and when not to, given these varying conditions. In order to better understand the growth release mechanism of dormant tissue at the molecular and physiological levels, molecular markers can be used. One gene family that has a long association with dormancy, which is routinely used as a marker for dormancy release, is DRM1/ARP (dormancyassociated gene-1/auxin-repressed protein). This plant-specific gene family has high sequence identity at the protein level throughout several plant species, but its function in planta remains undetermined. This review brings together and critically analyzes findings on the DRM1/ARP family from a number of species. We focus on the relevance of this gene as a molecular marker for dormancy, raising questions of what its role might actually be in the plant.