Short Communication: Analysis of the chromosome numbers of Zinnia elegans Jacq. in single, double, and pom-pom flowers

Saifudin, Shafira S, Dwiranti A, Salamah A. 2021. Short Communication: Analysis of the chromosome numbers of Zinnia elegans Jacq. in single, double, and pom-pom flowers. Biodiversitas 22: 2771-2777. Zinnia elegans Jacq. is highly valued as an ornamental plant with a variety of flower colors, sizes, and shapes. Polyploidization has been reported in Z. elegans with pom-pom flowers, nevertheless, the variation in chromosome numbers of various flower shapes has yet to be investigated. This study aimed to analyze the chromosome numbers of Z. elegans Jacq. cultivar “California Giant,” “Lilliput,” and “Cactus Flowered Mix” with single, double, and pom-pom flowers to determine their variations and identify the morphology of the flowers. Chromosomes were prepared using the squashing method, and images were analyzed using the Chromosome Image Analyzing System (CHIAS) IV. The minimum of 5 slides was prepared for each flower type from each cultivar. The results show that the three cultivars are diploid plants (2n = 24) with varying flower morphology. The single and double flowers of Z. elegans “Lilliput” and the single flower of “Cactus Flowered Mix” showed no variation in chromosome numbers. In contrast, chromosome number variation was found in the pom-pom flower of Z. elegans “California Giant” (2n = 22, 24, 48) and the double flower of “Cactus Flowered Mix” (2n = 9, 13, 15, 24). Two cultivars, Z. elegans “California Giant” and Z. elegans “Cactus Flowered Mix,” were successfully analyzed using CHIAS IV. Statistical analysis using a t-test (? = 0.05) showed that the total chromosome length of Z. elegans “California Giant” (2n = 24) was significantly greater than that of Z. elegans “Cactus Flowered Mix” (2n = 24). Chromosome satellites were found in both cultivars.

Morphological And Molecular Identification of Double Flowered Stock (Matthiola Incana R. Br) Cultivars With High Fertility

Garden stock (Matthiola incana R. Br.) is a commercially important horticultural crop owing to its ornamental effect. There are different stock cultivars varied in color and shape, especially flowered phenotype is an essential index evaluating its commercial value, because double flowered cultivars have more brilliant flowers compared to single flowered one. The present work aimed: (1) to make superior cultivars with different colors, high fertility, being capable of early selecting only double flowered seedlings by leaf color and to investigate morphological characteristics and (2) to select RAPD and ISSR primers for the cultivar certification and identification to culture and produce good commercial stock cultivars. Here we obtained new double flowered stock cultivars with different colors including pink, pale pink and white, through outcrossing between “white” cultivar (high fertile but unable to select double flower phenotype) and “pink” cultivar (vice. versa). Among newly obtained stock cultivars, single and double flower seedlings are distinguishable from each other by leaf color, having about 70% of fertility. Moreover RAPD and ISSR markers selected in this study can be applied to identify different stock cultivars in seed production, culture and to establish cultivar certification system.

Genome sequence of Hydrangea macrophylla and its application in analysis of the double flower phenotype

Owing to its high ornamental value, the double flower phenotype of hydrangea (Hydrangea macrophylla) is one of its most important traits. In this study, genome sequence information was obtained to explore effective DNA markers and the causative genes for double flower production in hydrangea. Single-molecule real-time sequencing data followed by a Hi-C analysis were employed. Two haplotype-phased sequences were obtained from the heterozygous genome of hydrangea. One assembly consisted of 3,779 scaffolds (2.256 Gb in length and N50 of 1.5 Mb), the other also contained 3,779 scaffolds (2.227 Gb in length, and N50 of 1.4 Mb). A total of 36,930 genes were predicted in the sequences, of which 32,205 and 32,222 were found in each haplotype. A pair of 18 pseudomolecules was constructed along with a high-density single-nucleotide polymorphism (SNP) genetic linkage map. Using the genome sequence data, and two F2 populations, the SNPs linked to double flower loci (djo and dsu) were discovered. DNA markers linked to djo and dsu were developed, and these could distinguish the recessive double flower allele for each locus, respectively. The LEAFY gene is a very likely candidate as the causative gene for dsu, since frameshift was specifically observed in the double flower accession with dsu.

Comparative Transcriptome and WGCNA Reveal Candidate Genes Involved in Petaloid Stamens in Paeonia Lactiflora

Background: The phenomenon of petaloid stamens in Paeonia lactiflora is an important cause of double flower formation. Although research on stamen development in model plants has progressed, the molecular mechanism of P. lactiflora petaloid stamens is still unclear. Results: In this study, a comparative transcriptomic analysis was performed on two cultivars of P. lactiflora (‘Fen Yu Nu’ and ‘Lian Tai’) with different stamen developmental patterns. Using transcriptome sequencing, 89,393 unigenes were identified in P. lactiflora. Trend analysis and weighted gene co-expression network analysis (WGCNA) indicated that 18 candidate genes were likely involved in petaloid stamens, including seven MADS-box genes PlAP3, PlDEFA, PlPI2, PlAG-1, PlSEP3, PlSEP1-1, and PlSEP1-2, and 11 transcription factors (TFs) PlTCP2, PlTCP4, PlTCP9, PlbHLH36, PlICE1, PlLBD38, PlNAC083, PlBLH11, PlPDF2, PlGBF1, and PlIIIA. Based on the selected candidate genes, a hypothetical model of gene expression network regulating petaloid stamens is proposed. Conclusions: Our results provide a collection of candidate genes for the analysis of P. lactiflora petaloid stamens, allowing for in-depth studies of the development pattern of P. lactiflora flower organs, and providing a theoretical basis for related research on petaloid stamens of other herbaceous flowers.

Genome sequence of Hydrangea macrophylla and its application in analysis of the double flower phenotype

Owing to its high ornamental value, the double flower phenotype of hydrangea (Hydrangea macrophylla) is one of its most important traits. In this study, genome sequence information was obtained to explore effective DNA markers and the causative genes for double flower production in hydrangea. Single molecule real-time sequencing data followed by a HiC analysis was employed. The resultant haplotype-phased sequences consisted of 3,779 sequences (2.256 Gb in length and N50 of 1.5 Mb), and 18 pseudomolecules comprising 1.08 Gb scaffold sequences along with a high-density SNP genetic linkage map. Using the genome sequence data obtained from two breeding populations, the SNPs linked to double flower loci (Djo and Dsu), were discovered for each breeding population. DNA markers J01 linked to Djo and S01 linked to Dsu were developed, and these could be used successfully to distinguish the recessive double flower allele for each locus respectively. The LEAFY gene was suggested as the causative gene for Dsu, since frameshift was specifically observed in double flower accession with dsu. The genome information obtained in this study will facilitate a wide range of genomic studies on hydrangea in the future.

Say it with double flowers

This article comments on: Gattolin, S, Cirilli M, Chessa S, et al. 2020. Mutations in orthologous PETALOSA TOE-type genes cause dominant double-flower phenotype in phylogenetically distant eudicots. Journal of Experimental Botany 71, 2585–2595.

Mapping a double flower phenotype-associated gene DcAP2L in Dianthus chinensis

The double flower is a highly important breeding trait that affects the ornamental value in many flowering plants. To get a better understanding of the genetic mechanism of double flower formation in Dianthus chinensis, we have constructed a high-density genetic map using 140 F2 progenies derived from a cross between a single flower genotype and a double flower genotype. The linkage map was constructed using double-digest restriction site-associated DNA sequencing (ddRAD-seq) with 2353 single nucleotide polymorphisms (SNPs). Quantitative trait locus (QTL) mapping analysis was conducted for 12 horticultural traits, and major QTLs were identified for nine of the 12 traits. Among them, two major QTLs accounted for 20.7% and 78.1% of the total petal number variation, respectively. Bulked segregant RNA-seq (BSR-seq) was performed to search accurately for candidate genes associated with the double flower trait. Integrative analysis of QTL mapping and BSR-seq analysis using the reference genome of Dianthus caryophyllus suggested that an SNP mutation in the miR172 cleavage site of the A-class flower organ identity gene APETALA2 (DcAP2L) is responsible for double flower formation in Dianthus through regulating the expression of DcAG genes.

Mutations in orthologous PETALOSA TOE-type genes cause a dominant double-flower phenotype in phylogenetically distant eudicots

The double-flower phenotype has been selected by humans for its attractiveness in various plant species and it is of great commercial value for the ornamental market. In this study we investigated the genetic determinant of the dominant double-flower trait in carnation, petunia, and Rosa rugosa, and identified mutant alleles of TARGET OF EAT (TOE)-type genes characterized by a disruption of the miR172 target sequence and of the C-terminal portion of the encoded protein. Despite the phylogenetic distance between these eudicots, which diverged in the early Cretaceous, the orthologous genes carrying these mutations all belong to a single TOE-type subgroup, which we name as PETALOSA (PET). Homology searches allowed us to identify PET sequences in various other species. To confirm the results from naturally occurring mutations, we used CrispR-Cas9 to induce lesions within the miR172 target site of Nicotiana tabacum PET genes, and this resulted in the development of supernumerary petaloid structures. This study describes pet alleles in economically important ornamental species and provides evidence about the possibility of identifying and engineering PET genes to obtain the desirable double-flower trait in different plants.