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The TIFY gene family (formerly known as the zinc finger proteins expressed in inflorescence meristem (ZIM) family) not only functions in plant defense responses but also are widely involved in regulating plant growth and development. However, the identification and functional analysis of TIFY proteins remain unexplored in Orchidaceae. Here, we identified 19 putative TIFY genes in the Phalaenopsis aphrodite genome. The phylogenetic tree classified them into four subfamilies: 14 members from JAZ, 3 members from ZML, and 1 each from PPD and TIFY. Sequence analysis revealed that all Phalaenopsis TIFY proteins contained a TIFY domain. Exon-intron analysis showed that the intron number and length of Phalaenopsis TIFY genes varied, whereas the same subfamily and subgroup genes had similar exon or intron numbers and distributions. The most abundant cis -elements in the promoter regions of the 19 TIFY genes were associated with light responsiveness, followed by MeJA and ABA, indicating their potential regulation by light and phytohormones. The 13 candidate TIFY genes screened from the transcriptome data exhibited two types of expression trends, suggesting their different roles in cell proliferation and cell expansion of floral organ growth during Phalaenopsis flower opening. Overall, this study serves as a background for investigating the underlying roles of TIFY genes in floral organ growth in Phalaenopsis .

Despite extensive research on orchid reproductive strategies, the genetic studies of sex differentiation in the orchid family are still lacking. In this study, we compared three sexual phenotypes of Cymbidium tortisepalum bisexual flowers as well as female and male unisexual mutants. Through comparative transcriptomes, we analyzed the sex-biased differentially expressed genes (DEGs) and gene co-expression networks of sex organs (gynostemium and ovary) among them, identified the candidate genes of sex differentiation, and validated their expression by qRT-PCR. The C. tortisepalum unisexual mutants with degenerated phenotypes were compared to the bisexual plants with respect to both the flower organs and plant morphologies. Totally, 12,145, 10,789, and 14,447 genes were uniquely expressed in the female, male, and hermaphrodite sex organs, respectively. A total of 4291 sex-biased DEGs were detected among them, with 871, 2867, and 1937 DEGs in the comparisons of bisexual vs. female, bisexual vs. male, and male vs. female flowers, respectively. Two co-expressed network modules, with 81 and 419 genes were tightly correlated with female sexual traits, while two others with 265 and 135 genes were highly correlated with male sexual traits. Two female-biased hub genes (CtSDR3b and CtSDR3b-like) nested in the female modules, the homologs of maize sex determinant tasselseed2, may control the feminization of C. tortisepalum. At the same time, two male-biased hub genes (CtYAB2 and CtYAB5) nested in the male modules, the homologs of grape sex determinant VviYABBY3, may control the androphany of C. tortisepalum. This study discovered the molecular regulation networks and proposed a model for orchid sex differentiation, therefore providing for the first time the genetic basis for the sex separation in the orchid family. [ABSTRACT FROM AUTHOR]

Orchids are the flowers of magnetic beauty. Vivid and attractive flowers with magnificent shapes make them the king of the floriculture industry. However, the long-awaited flowering is a drawback to their market success, and therefore, flowering time regulation is the key to studies about orchid flower development. Although there are some rare orchids with a continuous flowering pattern, the molecular regulatory mechanisms are yet to be elucidated to find applicable solutions to other orchid species. Multiple regulatory pathways, such as photoperiod, vernalization, circadian clock, temperature and hormonal pathways are thought to signalize flower timing using a group of floral integrators. This mini review, thus, organizes the current knowledge of floral time regulators to suggest future perspectives on the continuous flowering mechanism that may help to plan functional studies to induce flowering revolution in precious orchid species. [ABSTRACT FROM AUTHOR]

Human beings have disturbed the original characters of plants through interspecies hybridization, especially for economically producing cultivars with enhanced traits. Phalaenopsis is remoulded for exquisite flowers with huge shape and popular colors. However, the current challenge in Phalaenopsis breeding is that existing varieties tend to lose their original floral scent during the complex process of super-paraent hybridization. To address this, we collected a wide range of native species and hybrids to form the composition background and correlated the dynamics of Phalaenopsis fragrance for the futher breeding. A total of 208 volatile organic compounds (VOCs), with 83 prominent compounds constituting about 40 % of the identified substances. The primary species included all three major classes of floral fragrance compounds, with native species accounting for 83.33 % of volatile compounds released at levels exceeding 100 ng g−1 h−1. Both primary species and cultivars exhibited distinct aroma profiles, characterized by ten specific substances. Phalaenopsis stobartiana , originating from China, shows potential for benzenoid scents in fragrant flower breeding. On the other hand, hybrids primarily consisted of terpenoids and contained a higher abundance of low-threshold floral fragrance compounds. We also observed significant correlations between terpenoid and benzenoid scents with respect to color and flower shape. The height and width of the plants also showed a significant negative correlation with phenylpropanoid/ benzenoids and nitrogen-containing scent compounds. By conducting an extensive investigation into floral fragrance detection, we were able to concisely present the interrelationships among various characteristics of Phalaenopsis. This endeavor lays a primary foundation for exploring polymorphism in floral scent, providing guidance in Phalaenopsis breeding and facilitating ongoing genome-based molecular design for cultivating high-quality and fragrant orchids. [Display omitted] • Primary species and cultivars exhibited distinct aroma profiles separated by ten main characteristic substances. • Metabolic shunting and hybridization origin are possible reasons for the loss of floral fragrances in Phalaenopsis cultivars. • Phalaenopsis stobartiana can be prospective parent to make up for the benzenoid floral substances of Phalaenopsis. [ABSTRACT FROM AUTHOR]

• Cymbidium orchids are the most valuable flowers with a long vegetative phase (2–3 years). • We obtained leafless flowers for three Cymbidium species through a special media combination in tissue culture. These can be excellent resources to study abiotic stress tolerance. • Comparative transcriptome between leafless flowers and healthy leaves provides important clues about melatonin-mediated flowering, which has not been documented before in orchids. • A number of DEGs were found for Tryptophan pathway with contrasting expression patterns between leafless flowers and healthy leaves of three Cymbidium species. Abiotic stress is a major constraint in the successful growth and development of ornamental plants under severe conditions. Since antiquity, melatonin homeostasis has been an effective contrivance in the strategies of abiotic stress tolerance in plants, although it is completely neglected in orchids, the champagne of flowers. Orchids with exceptionally long vegetative phase face a number of stresses and, therefore, stress alleviation has been a hot topic in orchid cultivation. The in-vitro flowering is a useful method for early identification of hybrids in crop improvement programs. We successfully achieved in-vitro leafless flowering in three Cymbidium orchids (C. sinense, C. goeringii and C. ensifolium), which are elite flowers in terms of versatile flower shapes, esthetic preference and price. Transcriptomic analysis was performed to compare the leafless flowers with leaves to identify genes related to tryptophan pathway and melatonin biosynthesis. More than 50 differentially expressed genes (DEGs) were identified in each species with contrasting expressions in the leafless flowers and leaves. The important melatonin pathway genes included serotonin N-acetyltransferase (SNAT), caffeic acid 3-O-methyltransferase (CAMT) and tryptophan decarboxylase (TDC). Moreover, clustering analysis pointed out the significant abiotic stress tolerance-related genes. This opening report, thus, provides a robust cradle to idealize the melatonin as an effective abiotic stress regulator to aid the long journey of vegetative growth and then flowering in precious orchids. [ABSTRACT FROM AUTHOR]