Bud dormancy is an evolved trait that confers adaptation to harsh environments, and affects flower differentiation, crop yield and vegetative growth in perennials. ABA is a stress hormone and a major regulator of dormancy. Although the physiology of bud dormancy is complex, several advancements have been achieved in this field recently by using genetics, omics and bioinformatics methods. Here, we review the current knowledge on the role of ABA and environmental signals, as well as the interplay of other hormones and sucrose, in the regulation of this process. We also discuss emerging potential mechanisms in this physiological process, including epigenetic regulation.

Class I BPCs repress FUSCA3 during reproductive and seed development to promote ovule development while coordinating embryo and endosperm growth.

Lilies are economically important monocots known for their ornamental flowers, bulbs, and large genomes. The absence of their genomic information has impeded evolutionary studies and genome-based breeding efforts. Here, we present reference genomes for Lilium sargentiae (lily, 35.66 Gb) and Gloriosa superba (flame lily, 5.09 Gb). The giant lily genome is shaped by recent long terminal repeat retroelements. Phylogenetic analysis reveals diverse, independent origins of lily cultivars. Gene families involved in sucrose and starch metabolism are significantly expanded in the lily genome. Key homologs of XTH22, SOC1, and AP1/FUL-like genes regulate the development, bud growth transition, and floral bud growth transition of lily bulbs. Colchicine biosynthetic gene clusters are identified in G. superba but are absent in L. sargentiae, highlighting independent colchicine evolution in Colchicaceae. These genomic insights enhance understanding of Liliales evolution, providing a foundation for future breeding and molecular research.

Understanding corm development in flower bulbs is of importance for securing the quality of cut flowers and propagation of commercial stocks. Gladiolus is one of the most popular bulb plants worldwide. Its corm development is characterized by starch accumulation. Previous research has shown that phytohormones (especially gibberellin (GA)) are involved in tuber development. However, the relationship between abscisic acid (ABA)/GA and starch during corm development remains unclear. To gain deeper insights into the biological process of corm development, we performed a detailed anatomical characterization of different stages of corm development and analyzed phytohormone levels. Our study showed that corm development is linked to hormones (ABA and GA) and carbohydrates (sucrose and starch). Exogenous hormone treatment and silencing of endogenous hormone biosynthesis genes indicated that ABA positively regulates corm development, while GA acts as an antagonist of ABA function. A sucrose synthase gene (GhSUS2) was shown to be involved in the antagonism between ABA and GA. GhSUS2 was upregulated by ABA and downregulated by GA. The increase in the transcript level of GhSUS2 coincided with the development of corm/cormels. Silencing of GhSUS2 repressed corm development and starch accumulation. In conclusion, we propose that GhSUS2, an essential enzyme in sucrose degradation, is differentially regulated by ABA and GA and controls corm development in Gladiolus.

Dormancy is one of the least understood phenomena in plant biology, however bud/corm dormancy is an important economic trait in agricultural/horticultural breeding. In this study, we isolated an abscisic acid (ABA) biosynthesis gene, GhNCED, from the transcriptome database of corm dormancy release (CDR), and characterized its negative role in regulating CDR. To understand transcriptional regulation of GhNCED, yeast one-hybrid screening was conducted and GhTCP19 was identified and shown to directly regulate GhNCED expression. In planta assay showed that GhTCP19 negatively regulates GhNCED expression. GhTCP19 is dramatically induced by exogenous cytokinins (CK) and is induced during CDR. Silencing of GhTCP19 in dormant cormels delayed CDR, resulting in higher expression of GhNCED and ABA levels. Meanwhile, endogenous CK biosynthesis and signaling were inhibited in GhTCP19-silenced cormels. Taken together, our results reveal that GhTCP19 is a positive regulator of the CDR process by repressing an ABA biosynthesis gene’s expression (GhNCED) and promoting CK biosynthesis (GhIPT), signal transduction (GhARR), as well as cyclin genes. This study expands our knowledge on corm dormancy release which is mediated by TCP family members.