Floral color polymorphism can provide great insight into species evolution from a genetic and ecological standpoint. Color variations between species are often mediated by pollinators and are fixed characteristics, indicating their relevance to adaptive evolution, especially between plants within a single population or between similar species. The orchid genus Pleione has a wide variety of flower colors, from violet, rose-purple, pink, to white, but their color formation and its evolutionary mechanism are unclear. Here, we selected the P. limprichtii population in Huanglong, Sichuan Province, China, which displayed three color variations: Rose-purple, pink, and white, providing ideal material for exploring color variations with regard to species evolution. We investigated the distribution pattern of the different color morphs. The ratio of rose-purple:pink:white-flowered individuals was close to 6:3:1. We inferred that the distribution pattern may serve as a reproductive strategy to maintain the population size. Metabolome analysis was used to reveal that cyanindin derivatives and delphidin are the main color pigments involved. RNA sequencing was used to characterize anthocyanin biosynthetic pathway-related genes and reveal different color formation pathways and transcription factors in order to identify differentially-expressed genes and explore their relationship with color formation. In addition, qRT-PCR was used to validate the expression patterns of some of the genes. The results show that PlFLS serves as a crucial gene that contributes to white color formation and that PlANS and PlUFGT are related to the accumulation of anthocyanin which is responsible for color intensity, especially in pigmented flowers. Phylogenetic and co-expression analyses also identified a R2R3-MYB gene PlMYB10, which is predicted to combine with PlbHLH20 or PlbHLH26 along with PlWD40-1 to form an MBW protein complex (MYB, bHLH, and WDR) that regulates PlFLS expression and may serve as a repressor of anthocyanin accumulation-controlled color variations. Our results not only explain the molecular mechanism of color variation in P. limprichtii, but also contribute to the exploration of a flower color evolutionary model in Pleione, as well as other flowering plants.

Pleione (Orchidaceae) is not only famous for the ornamental value in Europe because of its special color, but also endemic in Southern Asia for its use in traditional medicine. A great deal of research about its secondary metabolites and biological activities has been done on only three of 30 species of Pleione. Up to now, 183 chemical compounds, such as phenanthrenes, bibenzyls, glucosyloxybenzyl succinate derivatives, flavonoids, lignans, terpenoids, etc., have been obtained from Pleione. These compounds have been demonstrated to play a significant role in anti-tumor, anti-neurodegenerative and anti-inflammatory biological activities and improve immunity. In order to further develop the drugs and utilize the plants, the chemical structural analysis and biological activities of Pleione are summarized in this review.

The wood sorrel family, Oxalidaceae, is mainly composed of annual or perennial herbs, a few shrubs, and trees distributed from temperate to tropical zones. Members of Oxalidaceae are of high medicinal, ornamental, and economic value. Despite the rich diversity and value of Oxalidaceae, few molecular markers or plastomes are available for phylogenetic analysis of the family. Here, we reported four new whole plastomes of Oxalidaceae and compared them with plastomes of three species in the family, as well as the plastome of Rourea microphylla in the closely related family Connaraceae. The eight plastomes ranged in length from 150,673 bp (Biophytum sensitivum) to 156,609 bp (R. microphylla). Genome annotations revealed a total of 129–131 genes, including 83–84 protein-coding genes, eight rRNA genes, 37 tRNA genes, and two to three pseudogenes. Comparative analyses showed that the plastomes of these species have minor variations at the gene level. The smaller plastomes of herbs B. sensitivum and three Oxalis species are associated with variations in IR region sizes, intergenic region variation, and gene or intron loss. We identified sequences with high variation that may serve as molecular markers in taxonomic studies of Oxalidaceae. The phylogenetic trees of selected superrosid representatives based on 76 protein-coding genes corroborated the Oxalidaceae position in Oxalidales and supported it as a sister to Connaraceae. Our research also supported the monophyly of the COM (Celastrales, Oxalidales, and Malpighiales) clade.

Background: Members of the plant-specific YABBY gene family are thought to play an important role in the development of leaf, flower, and fruit. The YABBY genes have been characterized and regarded as vital contributors to fruit development in Arabidopsis thaliana and tomato, in contrast to that in the important tropical economic fruit star fruit (Averrhoa carambola), even though its genome is available. Methods: In the present study, a total of eight YABBY family genes (named from AcYABBY1 to AcYABBY8) were identified from the genome of star fruit, and their phylogenetic relationships, functional domains and motif compositions, physicochemical properties, chromosome locations, gene structures, protomer elements, collinear analysis, selective pressure, and expression profiles were further analyzed. Results: Eight AcYABBY genes (AcYABBYs) were clustered into five clades and were distributed on five chromosomes, and all of them had undergone negative selection. Tandem and fragment duplications rather than WGD contributed to YABBY gene number in the star fruit. Expression profiles of AcYABBYs from different organs and developmental stages of fleshy fruit indicated that AcYABBY4 may play a specific role in regulating fruit size. These results emphasize the need for further studies on the functions of AcYABBYs in fruit development.

Phalaenopsis orchids, belonging to the Orchidaceae family, one of the largest groups of angiosperms, possess significant commercial value due to their fascinating flowers. Petal size is a vital trait that directly determines flower size and shape of Phalaenopsis. However, the genetic and developmental regulation of petal size in Phalaenopsis remains unexplored. In this study, we tracked the petal growth pattern through five stages of flower opening, discovering that cell division stops at stage 2 and stages 3 to 5 are the critical periods of rapid petal expansion. RNA-seq was then conducted to further reveal the molecular mechanisms underlying petal size regulation. Gene ontology (GO) analysis indicated that the differentially expressed genes (DEGs) from the four comparable groups were both enriched in terms related to cell expansion. Endogenous hormone assays showed that auxin, cytokinin, and gibberellin were implicated in the petal growth of Phalaenopsis. Moreover, six auxin signaling pathway genes, 11 cell expansion-related genes, and 30 transcription factors (TFs) identified through trend analysis were abundantly expressed during the critical period of petal expansion, suggesting that they may influence petal size by regulating cell expansion. In contrast, 18 TFs exhibited the highest expression levels at the S1 stage, indicating their potential role in petal cell proliferation. Based on weighted gene co-expression network analysis (WGCNA), six hub genes (PaLOF2, PaSWEET11, PaVNI2, PaHDA3, PaPMEI3, PaXTH30) were screened from the green and yellow module which was highly associated with the petal size. Our results lay a foundation for further exploration of the molecular mechanisms regulating petal size development and are significant for molecular breeding programs aimed at generating novel Phalaenopsis with desirable traits.