The Evolution of the WUSCHEL-Related Homeobox Gene Family in Dendrobium Species and Its Role in Sex Organ Development in D. chrysotoxum.

The WUSCHEL-related homeobox (WOX) transcription factor plays a vital role in stem cell maintenance and organ morphogenesis, which are essential processes for plant growth and development. Dendrobium chrysotoxum, D. huoshanense, and D. nobile are valued for their ornamental and medicinal properties. However, the specific functions of the WOX gene family in Dendrobium species are not well understood. In our study, a total of 30 WOX genes were present in the genomes of the three Dendrobium species (nine DchWOXs, 11 DhuWOXs, and ten DnoWOXs). These 30 WOXs were clustered into ancient clades, intermediate clades, and WUS/modern clades. All 30 WOXs contained a conserved homeodomain, and the conserved motifs and gene structures were similar among WOXs belonging to the same branch. D. chrysotoxum and D. huoshanense had one pair of fragment duplication genes and one pair of tandem duplication genes, respectively; D. nobile had two pairs of fragment duplication genes. The cis-acting regulatory elements (CREs) in the WOX promoter region were mainly enriched in the light response, stress response, and plant growth and development regulation. The expression pattern and RT-qPCR analysis revealed that the WOXs were involved in regulating the floral organ development of D. chrysotoxum. Among them, the high expression of DchWOX3 suggests that it might be involved in controlling lip development, whereas DchWOX5 might be involved in controlling ovary development. In conclusion, this work lays the groundwork for an in-depth investigation into the functions of WOX genes and their regulatory role in Dendrobium species' floral organ development.

Genome-Wide Identification of PEBP Gene Family in Two Dendrobium Species and Expression Patterns in Dendrobium chrysotoxum.

The PEBP gene family plays a significant role in regulating flower development and formation. To understand its function in Dendrobium chrysotoxum and D. nobile flowering, we identified 22 PEBP genes (11 DchPEBPs and 11 DnoPEBPs) from both species. We conducted analyses on their conserved domains and motifs, phylogenetic relationships, chromosome distribution, collinear correlation, and cis elements. The classification results showed that the 22 PEBPs were mainly divided into three clades, as follows: FT, MFT, and TFL1. A sequence analysis showed that most PEBP proteins contained five conserved domains, while a gene structure analysis revealed that 77% of the total PEBP genes contained four exons and three introns. The promoter regions of the 22 PEBPs contained several cis elements related to hormone induction and light response. This suggests these PEBPs could play a role in regulating flower development by controlling photoperiod and hormone levels. Additionally, a collinearity analysis revealed three pairs of duplicate genes in the genomes of both D. chrysotoxum and D. nobile. Furthermore, RT-qPCR has found to influence the regulatory effect of DchPEBPs on the development of flower organs (sepals, petals, lip, ovary, and gynostemium) during the flowering process (bud, transparent stage, and initial bloom). The results obtained imply that DchPEBP8 and DchPEBP9 play a role in the initial bloom and that DchPEBP7 may inhibit flowering processes. Moreover, DchPEBP9 may potentially be involved in the development of reproductive functionality. PEBPs have regulatory functions that modulate flowering. FT initiates plant flowering by mediating photoperiod and temperature signals, while TFL1 inhibits flowering processes. These findings provide clues for future studies on flower development in Dendrobium.

Genome-Wide Identification of TCP Gene Family in Dendrobium and Their Expression Patterns in Dendrobium chrysotoxum.

The TCP gene family are plant-specific transcription factors that play important roles in plant growth and development. Dendrobium chrysotoxum, D. nobile, and D. huoshanense are orchids with a high ornamental value, but few studies have investigated the specific functions of TCPs in Dendrobium flower development. In this study, we used these three Dendrobium species to analyze TCPs, examining their physicochemical properties, phylogenetic relationships, gene structures, and expression profiles. A total of 50 TCPs were identified across three Dendrobium species; they were divided into two clades-Class-I (PCF subfamily) and Class-II (CIN and CYC/TB1 subfamilies)-based on their phylogenetic relationships. Our sequence logo analysis showed that almost all Dendrobium TCPs contain a conserved TCP domain, as well as the existence of fewer exons, and the cis-regulatory elements of the TCPs were mostly related to light response. In addition, our transcriptomic data and qRT-PCR results showed that DchTCP2 and DchTCP13 had a significant impact on lateral organs. Moreover, changes in the expression level of DchTCP4 suggested its important role in the phenotypic variation of floral organs. Therefore, this study provides a significant reference for the further exploration of TCP gene functions in the regulation of different floral organs in Dendrobium orchids.

Genome-Wide Identification and Expression Analysis of the SPL Gene Family in Three Orchids.

SPL transcription factors regulate important processes such as plant growth and development, metabolic regulation, and abiotic stress. They play crucial roles in the development of flower organs. However, little is known about the characteristics and functions of the SPLs in the Orchidaceae. In this study, Cymbidium goeringii Rchb. f., Dendrobium chrysotoxum Lindl., and Gastrodia elata BI. were used as research objects. The SPL gene family of these orchids was analyzed on a genome-wide scale, and their physicochemical properties, phylogenetic relationships, gene structures, and expression patterns were studied. Transcriptome and qRT-PCR methods were combined to investigate the regulatory effect of SPLs on the development of flower organs during the flowering process (bud, initial bloom, and full bloom). This study identifies a total of 43 SPLs from C. goeringii (16), D. chrysotoxum (17), and G. elata (10) and divides them into eight subfamilies according to the phylogenetic tree. Most SPL proteins contained conserved SBP domains and complex gene structures; half of the genes had introns longer than 10 kb. The largest number and variety of cis-acting elements associated with light reactions were enriched, accounting for about 45% of the total (444/985); 13/43 SPLs contain response elements of miRNA156. GO enrichment analysis showed that the functions of most SPLs were mainly enriched in the development of plant flower organs and stems. In addition, expression patterns and qRT-PCR analysis suggested the involvement of SPL genes in the regulation of flower organ development in orchids. There was little change in the expression of the CgoSPL in C. goeringii, but DchSPL9 and GelSPL2 showed significant expression during the flowering process of D. chrysotoxum and G. elata, respectively. In summary, this paper provides a reference for exploring the regulation of the SPL gene family in orchids.

Genome-Wide Identification of the YABBY Gene Family in Dendrobium Orchids and Its Expression Patterns in Dendrobium chrysotoxum.

The small plant-specific YABBY gene family plays key roles in diverse developmental processes in plants. Dendrobium chrysotoxum, D. huoshanense, and D. nobile are perennial herbaceous plants belonging to Orchidaceae with a high ornamental value. However, the relationships and specific functions of the YABBY genes in the Dendrobium species remain unknown. In this study, six DchYABBYs, nine DhuYABBYs, and nine DnoYABBYs were identified from the genome databases of the three Dendrobium species, which were unevenly distributed on five, eight, and nine chromosomes, respectively. The 24 YABBY genes were classified into four subfamilies (CRC/DL, INO, YAB2, and FIL/YAB3) based on their phylogenetic analysis. A sequence analysis showed that most of the YABBY proteins contained conserved C2C2 zinc-finger and YABBY domains, while a gene structure analysis revealed that 46% of the total YABBY genes contained seven exons and six introns. All the YABBY genes harbored a large number of Methyl Jasmonate responsive elements, as well as anaerobic induction cis-acting elements in the promoter regions. Through a collinearity analysis, one, two, and two segmental duplicated gene pairs were identified in the D. chrysotoxum, D. huoshanense, and D. nobile genomes, respectively. The Ka/Ks values of these five gene pairs were lower than 0.5, indicating that the Dendrobium YABBY genes underwent negative selection. In addition, an expression analysis revealed that DchYABBY2 plays a role in ovary and early-stage petal development, while DchYABBY5 is essential for lip development and DchYABBY6 is crucial for early sepal formation. DchYABBY1 primarily regulates sepals during blooming. Furthermore, there is the potential involvement of DchYABBY2 and DchYABBY5 in gynostemium development. The results of a comprehensive genome-wide study would provide significant clues for future functional investigations and pattern analyses of YABBY genes in different flower parts during flower development in the Dendrobium species.

Genomic Resequencing Unravels the Genetic Basis of Domestication, Expansion, and Trait Improvement in Morus Atropurpurea.

Mulberry is an economically important plant in the sericulture industry and traditional medicine. However, the genetic and evolutionary history of mulberry remains largely unknown. Here, this work presents the chromosome-level genome assembly of Morus atropurpurea (M. atropurpurea), originating from south China. Population genomic analysis using 425 mulberry accessions reveal that cultivated mulberry is classified into two species, M. atropurpurea and M. alba, which may have originated from two different mulberry progenitors and have independent and parallel domestication in north and south China, respectively. Extensive gene flow is revealed between different mulberry populations, contributing to genetic diversity in modern hybrid cultivars. This work also identifies the genetic architecture of the flowering time and leaf size. In addition, the genomic structure and evolution of sex-determining regions are identified. This study significantly advances the understanding of the genetic basis and domestication history of mulberry in the north and south, and provides valuable molecular markers of desirable traits for mulberry breeding.

Genome-wide identification and expression analysis of the GRAS gene family in Dendrobium chrysotoxum.

The GRAS gene family encodes transcription factors that participate in plant growth and development phases. They are crucial in regulating light signal transduction, plant hormone (e.g. gibberellin) signaling, meristem growth, root radial development, response to abiotic stress, etc. However, little is known about the features and functions of GRAS genes in Orchidaceae, the largest and most diverse angiosperm lineage. In this study, genome-wide analysis of the GRAS gene family was conducted in Dendrobium chrysotoxum (Epidendroideae, Orchidaceae) to investigate its physicochemical properties, phylogenetic relationships, gene structure, and expression patterns under abiotic stress in orchids. Forty-six DchGRAS genes were identified from the D. chrysotoxum genome and divided into ten subfamilies according to their phylogenetic relationships. Sequence analysis showed that most DchGRAS proteins contained conserved VHIID and SAW domains. Gene structure analysis showed that intronless genes accounted for approximately 70% of the DchGRAS genes, the gene structures of the same subfamily were the same, and the conserved motifs were also similar. The Ka/Ks ratios of 12 pairs of DchGRAS genes were all less than 1, indicating that DchGRAS genes underwent negative selection. The results of cis-acting element analysis showed that the 46 DchGRAS genes contained a large number of hormone-regulated and light-responsive elements as well as environmental stress-related elements. In addition, the real-time reverse transcription quantitative PCR (RT-qPCR) experimental results showed significant differences in the expression levels of 12 genes under high temperature, drought and salt treatment, among which two members of the LISCL subfamily (DchGRAS13 and DchGRAS15) were most sensitive to stress. Taken together, this paper provides insights into the regulatory roles of the GRAS gene family in orchids.

Genome-wide analysis of the TCP gene family and their expression pattern in Cymbidium goeringii.

TCP gene family are specific transcription factors for plant, and considered to play an important role in development and growth. However, few related studies investigated the TCP gene trait and how it plays a role in growth and development of Orchidaceae. In this study, we obtained 14 TCP genes (CgTCPs) from the Spring Orchid Cymbidium goeringii genome. The classification results showed that 14 CgTCPs were mainly divided into two clades as follows: four PCF genes (Class I), nine CIN genes and one CYC gene (Class II). The sequence analysis showed that the TCP proteins of C. goeringii contain four conserved regions (basic Helix-Loop-Helix) in the TCP domain. The exon-intron structure varied in the clade according to a comparative investigation of the gene structure, and some genes had no introns. There are fewer CgTCP homologous gene pairs compared with Dendrobium catenatum and Phalaenopsis equestris, suggesting that the TCP genes in C. goeringii suffered more loss events. The majority of the cis-elements revealed to be enriched in the function of light responsiveness, followed by MeJA and ABA responsiveness, demonstrating their functions in regulating by light and phytohormones. The collinearity study revealed that the TCPs in D. catenatum, P. equestris and C. goeringii almost 1:1. The transcriptomic data and real-time reverse transcription-quantitative PCR (RT-qPCR) expression profiles showed that the flower-specific expression of the TCP class II genes (CgCIN2, CgCIN5 and CgCIN6) may be related to the regulation of florescence. Altogether, this study provides a comprehensive analysis uncovering the underlying function of TCP genes in Orchidaceae.