Hyacinth, one of the five best-selling bulbous flowers in the world, is a favored flower of garden landscapes in the spring. Hyacinth has a single origin, but there are many horticultural varieties. Physical mapping of ribosomal DNA (rDNA) and telomeric repeat loci by fluorescence in situ hybridization (FISH) is helpful to understand the genetic relationship and chromosome inheritance in hyacinth breeding. In this study, 45S rDNA, 5S rDNA and telomeric repeats were used as probes, the mitotic metaphase chromosomes of 8 diploid hyacinth cultivars were analyzed by FISH location, and their karyotype parameters were analyzed by Q-type cluster analysis. The results showed that two 45S rDNA loci were detected in all eight hyacinth cultivars, four 5S rDNA loci were detected in ‘Gypsy Queen’, and three were detected in other cultivars. In addition to the presence of telomere loci at both ends of chromosomes, seven telomere loci were detected in ‘Gypsy Princess’ and ‘Yellow Stone’, and eight telomere loci were detected in other cultivars. At the same time, when the euclidean distance between groups was 20, the eight hyacinth cultivars were clustered into three groups (‘Yellow Stone’, ‘Red Pearl’ and ‘Pink Pearl’), and ‘Gypsy Prince’ was a single group; the other four cultivars were in one group. The distribution of 45S rDNA loci in diploid hyacinth cultivars was relatively conservative, while the locus number and distribution of 5S rDNA and telomeric repeats were highly polymorphic. The FISH physical mapping in this study provides a basic understanding of the karyotype evolution of hyacinth species, which could increase the understanding of the evolutionary history and phylogenetic relationships of hyacinths.

Background: MicroRNA159 (miR159) is a conserved miRNA found in various plant species. By regulating GAMYB-like transcription factors, miR159 is involved in diverse biological processes. Cymbidium goeringii, a significant traditional Chinese orchid, has unique flower shape and elegant fragrance. However, its development has been several limited because of the low flower bud differentiation and the difficult reproduction. This research aims to provide guidance for the role of cgo-miR159 in reproductive organ development to enhance the ornamental and economic value of Cymbidium. Methods: In this study, miR159 was cloned and its expression was determined across different development stages and tissue types. The function of cgo-miR159 was identified using gene transformation in Arabidopsis and tobacco plants. Results: High expression levels of cgo-miR159 were detected in the leaves and stamens during reproductive growth and expression peaked during flower bud development when the flower was above 0.5 to 3 cm in length. In transgenic experiments, the ectopic expression of cgo-miR159 led to defective development in the stamens of model plants (Arabidopsis and tobacco), including earlier anther dehiscence and pollen deformity, which resulted in developmental abnormalities and reduced seeds count in fruits. Conclusions: In summary, cgo-miR159 affected the development of reproductive organs in model plants. This research complements previous studies on the function of miR159 and provide useful references for the genetic improvement of orchids.

Age-dependent flowering is a prominent feature of perennial orchids, yet its physiological and small RNA basis remains poorly understood in Cymbidium goeringii. Here, floral bud formation, carbohydrate contents, and endogenous hormones were examined across successive shoot age stages, and four representative stages were selected for small RNA sequencing. Floral bud formation showed a clear age-dependent rise-and-fall pattern, accompanied by distinct changes in carbohydrate and hormone levels. Small RNA sequencing identified 810 miRNAs, including 356 known and 454 putative novel miRNAs, of which 311 were differentially expressed. Temporal expression analysis grouped 210 DEMIs into four significant profiles, all showing reduced expression in the oldest shoots. Functional analysis of predicted targets highlighted starch and sucrose metabolism and plant hormone signal transduction, and further pathway analysis identified multiple predicted miRNA–target associations related to carbohydrate metabolism and hormone signaling. qRT-PCR analysis generally supported the sequencing-based expression patterns. These findings reveal coordinated age-related changes in flowering competence, physiological status, and miRNA expression, and identify candidate miRNAs and functional pathways potentially associated with age-dependent flowering in C. goeringii.