Drought is a major abiotic stress that limits plant growth and development. Adaptive mechanisms have evolved to mitigate drought stress, including the capacity to adjust water loss rate and to modify the morphology and structure of the epidermis. Here, we show that the expression of CmNF‐YB8, encoding a nuclear factor Y (NF‐Y) B‐type subunit, is lower under drought conditions in chrysanthemum (Chrysanthemum morifolium). Transgenic chrysanthemum lines in which transcript levels of CmNF‐YB8 were reduced by RNA interference (CmNF‐YB8‐RNAi) exhibited enhanced drought resistance relative to control lines, whereas lines overexpressing CmNF‐YB8 (CmNF‐YB8‐OX) were less tolerant to drought. Compared to wild type (WT), CmNF‐YB8‐RNAi plants showed reduced stomatal opening and a thicker epidermal cuticle that correlated with their water loss rate. We also identified genes involved in stomatal adjustment (CBL‐interacting protein kinase 6, CmCIPK6) and cuticle biosynthesis (CmSHN3) that are more highly expressed in CmNF‐YB8‐RNAi lines than in WT, CmCIPK6 being a direct downstream target of CmNF‐YB8. Virus‐induced gene silencing of CmCIPK6 or CmSHN3 in the CmNF‐YB8‐RNAi background abolished the effects of CmNF‐YB8‐RNAi on stomatal closure and cuticle deposition, respectively. CmNF‐YB8 thus regulates CmCIPK6 and CmSHN3 expression to alter stomatal movement and cuticle thickness in the leaf epidermis, thereby affecting drought resistance.

The gibberellins (GAs) receptor GA INSENSITIVE DWARF1 (GID1) plays a central role in GA signal perception and transduction. The typical photoperiodic plant chrysanthemum (Chrysanthemum morifolium) only flowers when grown in short-day photoperiods. In addition, chrysanthemum flowering is also controlled by the aging pathway, but whether and how GAs participate in photoperiod- and age-dependent regulation of flowering remain unknown. Here, we demonstrate that photoperiod affects CmGID1B expression in response to GAs and developmental age. Moreover, we identified PHOTOLYASE/BLUE LIGHT RECEPTOR2, an atypical photocleavage synthase, as a CRYPTOCHROME-INTERACTING bHLH1 interactor with which it forms a complex in response to short days to activate CmGID1B transcription. Knocking down CmGID1B raised endogenous bioactive GA contents and GA signal perception, in turn modulating the expression of the aging-related genes MicroRNA156 and SQUAMOSA PROMOTER BINDING PROTEIN-LIKE3. We propose that exposure to short days accelerates the juvenile-to-adult transition by increasing endogenous GA contents and response to GAs, leading to entry into floral transformation.

Petal senescence involves numerous programmed changes in biological and biochemical processes. Ubiquitination plays a critical role in protein degradation, a hallmark of organ senescence. Therefore, we investigated changes in the proteome and ubiquitome of senescing rose (Rosa hybrida) petals to better understand their involvement in petal senescence. Of 3859 proteins quantified in senescing petals, 1198 were upregulated, and 726 were downregulated during senescence. We identified 2208 ubiquitinated sites, including 384 with increased ubiquitination in 298 proteins and 1035 with decreased ubiquitination in 674 proteins. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that proteins related to peptidases in proteolysis and autophagy pathways were enriched in the proteome, suggesting that protein degradation and autophagy play important roles in petal senescence. In addition, many transporter proteins accumulated in senescing petals, and several transport processes were enriched in the ubiquitome, indicating that transport of substances is associated with petal senescence and regulated by ubiquitination. Moreover, several components of the brassinosteroid (BR) biosynthesis and signaling pathways were significantly altered at the protein and ubiquitination levels, implying that BR plays an important role in petal senescence. Our data provide a comprehensive view of rose petal senescence at the posttranslational level.

Chrysanthemum is one of the four major cut flowers in the world, with high ornamental and economic value. Fragrance is an important ornamental character of chrysanthemum flowers, especially those consumed as tea and other foods, and the flower fragrance is the major determinant of the commercial value of chrysanthemum cultivars. Currently, however, the research on chrysanthemum flower fragrance is mainly focused on the composition and content of fragrant compounds, and a clear classification of fragrance types is lacking. Here, we divided chrysanthemum fragrance into six categories based on sensory evaluation and determined the identity and content of fragrant compounds of chrysanthemum accessions representative of each fragrance type by GC-MS. In addition, we analyzed the conserved aromatic substances responsible for the fruity fragrance type chrysanthemum with multi-functional development potential, providing a theoretical basis for creating new chrysanthemum germplasm with specific fragrance types. The results of this study can accelerate the breeding process of chrysanthemum accessions with new fragrance types.

The decision to flower in chrysanthemum (Chrysanthemum morifolium) is controlled by the photoperiod imposed by the outside environment along with endogenous gibberellin levels. Small peptides have broad and critical functions throughout the plant life cycle, but whether and how small peptides are involved in photoperiod- and gibberellin-dependent regulation of flowering remain unclear. Here, we demonstrate that a GIBBERELLIC ACID-STIMULATED TRANSCRIPT (GAST) peptide family member, CmGAST1, promotes flowering in chrysanthemum by interacting with SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 9 (SPL9), a key regulator of flowering in the age-dependent pathway. CmGAST1 expression was induced under short-day photoperiods and by gibberellin treatment. In addition, we show that a negative regulator of GA signaling GIBBERELLIC ACID INSENSITIVE (GAI) interacts with CALMODULIN 7 (CAM7), a key factor in calcium signaling, and the resulting CmCAM7–GAI complex directly suppresses CmGAST1 expression. Notably, short-day photoperiods induce the accumulation of bioactive gibberellins and Ca2+ in the shoot apex, thereby inhibiting CmGAI and CmCAM7, respectively, and releasing their inhibition of CmGAST1 expression. We propose that the peptide CmGAST1 integrates gibberellin and calcium signals, coordinating the photoperiod and aging pathways to accelerate chrysanthemum maturation and flowering.