Background: Impatiens L. is a genus of complex taxonomy that belongs to the family Balsaminaceae (Ericales) and contains approximately 1000 species. The genus is well known for its economic, medicinal, ornamental, and horticultural value. However, knowledge about its germplasm identification, molecular phylogeny, and chloroplast genomics is limited, and taxonomic uncertainties still exist due to overlapping morphological features and insufficient genomic resources. Results: We sequenced the chloroplast genomes of six different species (Impatiens chlorosepala, Impatiens fanjingshanica, Impatiens guizhouensis, Impatiens linearisepala, Impatiens loulanensis, and Impatiens stenosepala) in the karst area of China and compared them with those of six previously published Balsaminaceae species. We contrasted genomic features and repeat sequences, assessed sequence divergence and constructed phylogenetic relationships. Except for those of I. alpicola, I. pritzelii and I. glandulifera, the complete chloroplast genomes ranging in size from 151,366 bp (I. alpicola) to 154,189 bp (Hydrocera triflora) encoded 115 distinct genes [81 protein-coding, 30 transfer RNA (tRNA), and 4 ribosomal RNA (rRNA) genes]. Moreover, the characteristics of the long repeat sequences and simple sequence repeats (SSRs) were determined. psbK-psbI, trnT-GGU-psbD, rpl36-rps8, rpoB-trnC-GCA, trnK-UUU-rps16, trnQ-UUG, trnP-UGG-psaJ, trnT-UGU-trnL-UAA, and ycf4-cemA were identified as divergence hotspot regions and thus might be suitable for species identification and phylogenetic studies. Additionally, the phylogenetic relationships based on Maximum likelihood (ML) and Bayesian inference (BI) of the whole chloroplast genomes showed that the chloroplast genome structure of I. guizhouensis represents the ancestral state of the Balsaminaceae family. Conclusion: Our study provided detailed information about nucleotide diversity hotspots and the types of repeats, which can be used to develop molecular markers applicable to Balsaminaceae species. We also reconstructed and analyzed the relationships of some Impatiens species and assessed their taxonomic statuses based on the complete chloroplast genomes. Together, the findings of the current study might provide valuable genomic resources for systematic evolution of the Balsaminaceae species.

Introduction: Flower color is one of the important ornamental traits in the plants, which plays an active role in attracting pollinators to pollinate plants and reproduce their offspring. The flower color of Impatiens uliginosa is rich, there are four main flower colors in nature: deep red, red, pink, and white. However, it remains unclear whether on four different flower colors mechanism of I. uliginosa.Methods: We investigate colorimetric measurement, observation of epidermal cells, cellular pH determination, extraction and determination of total anthocyanins and flavonoid, semi-quantitative determination of pigment components, and gene cloning and qRT-PCR of CHS genes to study four flower colors of I. uliginosa.Results: The L^* and b^* values were the highest in white flower, while the a^* values were the highest in pink flower. The same shape of epidermal cells was observed in different flower colors, which was all irregular flat polygons, and there were partial lignification. Their cellular pH values were weakly acidic, while the pH values of the deep red flower was the highest and the white flower was the lowest. The highest pigment content of the four flower colors was total anthocyanin content. And malvidin-3-galactosidechloride (C₂₃H₂₅ClO₁₂), cyanidin-3-O-glucoside (C₂₁H₂₁O₁₁) and delphinidin (C₁₅H₁₁O₇) were the main pigment components affecting the color of four different flower colors. The anthocyanin synthesis gene IuCHS was expressed in four flowers, and all three copies of it had the highest expression level in pink flower and the lowest expression level in white flower.Discussion: These results revealed the influence of main internal factors on four different flower colors of I. uliginosa, and provided a basis for further understanding of the intracellular and molecular regulatory mechanisms of flower color variation, and laid a foundation for the improvement of flower color breeding of Impatiens.

Impatiens L., the largest genus in the family Balsaminaceae with approximately 1,000 species, is a controversial genus. Due to the conflict of morphological features and insufficient genomic resources, the studies of systematic evolution and understanding of taxonomic identification are considered to be very limited. Hence, we have sequenced the complete chloroplast genomes of three ornamental species (Impatiens balsamina, I. hawkeri, and I. walleriana), and compared them with previously published wild species data. We performed a detailed comparison of a highly similar basic structure, size, GC content, gene number, order, and functional array among them. Similarly, most divergent genes were detected from previous work in the literature. The mutational regions containing highly variable nucleotide hotspots were identified and may be used as potential markers for species identification and taxonomy. Furthermore, using whole chloroplast genome data to analysis the phylogenetic relationship of the Balsaminaceae species, we found that they were all part of a single clade. The three phenotypically different ornamental species were clustered together, suggesting that they were very likely to be closely related. We achieved and characterized the plastid genome structure, identified the divergence hotspots, and determined the phylogenetic and taxonomic positions of the three cultivated species in the Impatiens genus. The results may show that the chloroplast genome can be used to solve phylogenetic problems in or between the Impatiens genus and also provide genomic resources for the study of the Balsaminaceae family’s systematics and evolution.

Impatiens L., the largest genus in the family Balsaminaceae with approximately 1000 species, is a controversial and complex genus that includes many economically important species well known for medicinal and ornamental values. However, there is limited knowledge of molecular phylogeny and chloroplast genomics, and uncertainties still exist at a taxonomic level. In this study, we have assembled four chloroplast genomics specimens of Impatiens cyanantha and Impatiens monticola, which are found at the different altitudes of Guizhou and Yunnan in China, and compared them with previously published three wild Balsaminaceae species (Impatiens piufanensis, Impatiens glandlifera, and Hydrocera triflora). The complete chloroplast genome sequences ranged from 152,236 bp (I. piufanensis) to 154,189 bp (H. triflora) and encoded 115 total distinct genes, of which 81 were protein-coding, 30 were distinct transfer RNA genes(tRNA), and 4 were ribosomal RNA genes (rRNA). A comparative analysis of I. cyanantha (Guizhou) vs. I. cyanantha (Yunnan) and I. monticola (Guizhou) vs. I. monticola (Yunnan) revealed minor changes in lengths; however, similar gene contents, gene orders, and GC contents existed among them. Interestingly, highly coding and non-coding genes, and regions matK, psbK, atpH-atpI, trnC-trnT, petN, psbM, atpE, rbcL, accD, psaL, rps3-rps19, ndhG-ndhA,rpl16, rpoB, ndhB, ndhF, ycf1, and ndhH were found, which could be suitable for identification of species and phylogenetic studies. During the comparison between I. cyanantha (Guizhou) and I. cyanantha (Yunnan), we observed that the rps4, ycf2, ndhF, ycf1, and rpoC2 genes underwent positive selection. Meanwhile, in the comparative study of I. monticola (Guizhou) vs. I. monticola (Yunnan), The accD and ycf1 genes were positively selected. Additionally, phylogenetic relationships based on maximum likelihood (ML) and Bayesian inference (BI) among whole chloroplast genomes showed that a sister relationship with I. monticola (Guizhou) and I. monticola (Yunnan) formed a clade with I.piufanensis proving their close connection. Besides, I.cyanantha (Guizhou) and I. cyanantha (Yunnan) formed a clade with I. glandlifera. Along with the findings and the results, the current study might provide valuable significant genomic resources for systematics and evolution of the genus impatiens in different altitudes of regions.

Background: Spur, a structure capable of producing and storing nectar, not only plays a vital role in the pollination process but also promotes the rapid diversification of some plant lineages, which is considered a key innovation in plants. Spur is the focus of many studies, such as evolution and ecological hypothesis, but the current understanding of spur development is limited. High-throughput sequencing of Impatiens uliginosa was carried out to study the molecular mechanism of its spur development, which is believed to provide some insights into the spur development of Impatiens. Results: Transcriptomic sequencing and analysis were performed on spurs and limbs of I. uliginosa at three developmental stages. A total of 47.83 Gb of clean data were obtained, and 49,716 unigene genes were assembled. After comparison with NR, Swiss-Prot, Pfam, COG, GO and KEGG databases, a total of 27,686 genes were annotated successfully. Through comparative analysis, 19,356 differentially expressed genes were found and enriched into 208 GO terms and 146 KEGG pathways, among which plant hormone signal transduction was the most significantly enriched pathway. One thousand thirty-two transcription factors were identified, which belonged to 33 TF families such as MYB, bHLH and TCP. Twenty candidate genes that may be involved in spur development were screened and verified by qPCR, such as SBP, IAA and ABP. Conclusions: Transcriptome data of different developmental stages of spurs were obtained, and a series of candidate genes related to spur development were identified. The importance of genes related to cell cycle, cell division, cell elongation and hormones in spur development was clarified. This study provided valuable information and resources for understanding the molecular mechanism of spur development in Impatiens.

Background: Impatiens is an important genus with rich species of garden plants, and its distribution is extremely extensive, which is reflected in its diverse ecological environment. However, the specific mechanisms of Impatiens’ adaptation to various environments and the mechanism related to lignin remain unclear. Results: Three representative Impatiens species,Impatiens chlorosepala (wet, low degree of lignification), Impatiens uliginosa (aquatic, moderate degree of lignification) and Impatiens rubrostriata (terrestrial, high degree of lignification), were selected and analyzed for their anatomical structures, lignin content and composition, and lignin-related gene expression. There are significant differences in anatomical parameters among the stems of three Impatiens species, and the anatomical structure is consistent with the determination results of lignin content. Furthermore, the thickness of the xylem and cell walls, as well as the ratio of cell wall thickness to stem diameter have a strong correlation with lignin content. The anatomical structure and degree of lignification in Impatiens can be attributed to the plant's growth environment, morphology, and growth rate. Our analysis of lignin-related genes revealed a negative correlation between the MYB4 gene and lignin content. The MYB4 gene may control the lignin synthesis in Impatiens by controlling the structural genes involved in the lignin synthesis pathway, such as HCT, C3H, and COMT. Nonetheless, the regulation pathway differs between species of Impatiens. Conclusions: This study demonstrated consistency between the stem anatomy of Impatiens and the results obtained from lignin content and composition analyses. It is speculated that MYB4 negatively regulates the lignin synthesis in the stems of three Impatiens species by regulating the expression of structural genes, and its regulation mechanism appears to vary across different Impatiens species. This study analyses the variations among different Impatiens plants in diverse habitats, and can guide further molecular investigations of lignin biosynthesis in Impatiens.