Search Results (10)

Apomixis-mediated fixation of heterosis could transform hybrid breeding in alfalfa (Medicago sativa), a globally important forage crop. The parthenogenesis-inducing morphogenetic regulator BABY BOOM (BBM) represents a promising candidate for enabling this advancement. Here, we identified BBM homologs from three alfalfa genomes, characterized their promoter regions, and cloned a 2082 bp MsBBM gene encoding a 694-amino acid nuclear-localized protein. Three alfalfa BBM gene promoters primarily contained light- and hormone-responsive elements. Phylogenetic and conserved domain analyses of the MsBBM protein revealed a high sequence similarity with M. truncatula BBM. Expression profiling demonstrated tissue-specific accumulation of MsBBM transcripts, with the highest expression in the roots and developing pods. Hormonal treatments differentially regulated MsBBM. Expression was upregulated by GA₃ (except at 4 h) and SA, downregulated by NAA, MeJA (both except at 8 h), and ABA (except at 4 h), while ETH treatment induced a transient expression peak at 2 h. As an AP2/ERF family transcription factor showing preferential expression in young embryos, MsBBM likely participates in reproductive development and may facilitate apomixis. These findings establish a molecular framework for exploiting MsBBM to enhance alfalfa breeding efficiency through heterosis fixation. Full article

Background/Objectives: BABY BOOM (BBM), a transcription factor from the APETALA2 (AP2) protein family, plays a critical role in somatic embryo induction and apomixis. BBM has now been widely applied to induce apomixis or enhance plant transformation and regeneration efficiency through overexpression or ectopic expression. However, the structural and functional evolutionary history of BBM genes in plants is still not well understood. Methods: The protein sequences of 10 selected plant species were used to locate the branch of BBM-Like by key domain identification and phylogenetic tree construction. The identified BBML genes were used for further conserved motif identification, gene structural analysis, miRNA binding site prediction, cis-acting element prediction, collinear analysis, protein–protein interaction network construction, three-dimensional structure modeling, molecular docking, and expression pattern analysis. Results: A total of 24 BBML proteins were identified from 10 representative plant species. Phylogenetic relationship analysis displayed that BBML proteins from eudicots and monocots were divided into two clusters, with monocots exhibiting a higher number of BBMLs. Gene duplication events indicated that whole genome/segmental duplication were the primary drivers of BBML genes’ evolution in the tested species, with purifying selection playing a key role during evolution processes. Comparative analysis of motif, domains, and gene structures revealed that most BBMLs were highly evolutionarily conserved. The expression patterns of BBML genes revealed significant tissue specificity, particularly in the root and embryo. We also constructed protein–protein interaction networks and molecular docking models to identify functional pathways and key amino acid residues of BBML proteins. The functions of BBMLs may differ between monocots and eudicots, as suggested by the functional enrichment of interacting proteins. Conclusions: Our research delved into the molecular mechanism, evolutionary relationships, functional differentiation, and expression patterns of BBML genes across plants, laying the groundwork for further investigations into the molecular properties and biological roles of BBMLs. Full article

BABY BOOM (BBM) is one of the members of the plant-specific APETALA2/ethylene-responsive factor (AP2/ERF) transcription factor superfamily. It acts as a key regulator of plant cell pluripotency, playing a significant role in promoting somatic embryogenesis. In this study, a BBM gene named PoBBM was screened, cloned, and identified from the third-generation full-length transcriptome data of Paeonia ostii. Its open reading frame was 2136 bp, encoding 711 amino acids. Sequence feature analysis revealed that it possessed two AP2 conserved domains and eight motifs, including bbm-1. The phylogenetic tree indicated that PoBBM clusters with AtBBM in the euANT group of the Arabidopsis AP2 family, which is most closely related to grape VvBBM and may have the same ancestry as grape. Subcellular localization demonstrated that the PoBBM protein was localized in the nucleus. Semi-quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to assess the PoBBM transcript levels during ten developmental stages of somatic embryos and in five tissue types of peonies. The results indicate that PoBBM was highly expressed in the early stages of peony somatic embryo development. The expression on 0–15 d was the highest and decreased gradually with somatic embryogenesis. The gene is almost not expressed after 40 d since somatic embryo formation. PoBBM was expressed in roots, stems, leaves, seeds, and calli, with the highest levels in seeds, followed by leaves and calli. The PoBBM protein displayed transcriptional self-activation activity, which may facilitate further research on its relationships with other proteins. The above results provide a key gene PoBBM for somatic embryogenesis in peonies, which is significant for advancing the establishment of a stable and efficient regeneration and genetic transformation system for peonies. Full article

Understanding the molecular mechanisms underlying somatic embryogenesis is essential for resolving the problems related to the long duration of the process and a low rate of somatic embryo induction in oil palm tissue culture. In this study, we conducted genome-wide identification of the oil palm homeodomain leucine zipper (EgHD-ZIP) family, which is one of the plant-specific transcription factors reported to be involved in embryogenesis. EgHD-ZIP proteins can be divided into four subfamilies, which have similarities in gene structure and protein-conserved motifs within a group. In silico expression analysis showed that the expression of EgHD-ZIP gene members in the EgHD-ZIP I and II families, as well as most members in the EgHD-ZIP IV family, were up-regulated during the zygotic and somatic embryo developmental stages. In contrast, the expression of EgHD-ZIP gene members in the EgHD-ZIP III family was down-regulated during zygotic embryo development. Moreover, the expression of EgHD-ZIP IV genes was validated in the oil palm callus and at the somatic embryo stages (globular, torpedo, and cotyledon). The results revealed that EgHD-ZIP IV genes were up-regulated at the late stages of somatic embryogenesis (torpedo and cotyledon). While BABY BOOM (BBM) gene was up-regulated at the early stage of somatic embryogenesis (globular). In addition, the Yeast-two hybrid assay revealed the direct binding between all members of the oil palm HD-ZIP IV subfamily (EgROC2, EgROC3, EgROC5, EgROC8, and EgBBM). Our findings suggested that the EgHD-ZIP IV subfamily and EgBBM work together to regulate somatic embryogenesis in oil palms. This process is important because it is widely used in plant biotechnology to produce large quantities of genetically identical plants, which can be used for oil palm tissue culture improvement. Full article

Although zygotic embryogenesis is usually studied in the field of seed biology, great attention has been paid to the methods used to generate haploid embryos due to their applications in crop breeding. These mainly include two methods for haploid embryogenesis: in vitro microspore embryogenesis and in vivo haploid embryogenesis. Although microspore culture systems and maize haploid induction systems were discovered in the 1960s, little is known about the molecular mechanisms underlying haploid formation. In recent years, major breakthroughs have been made in in vivo haploid induction systems, and several key factors, such as the matrilineal (MTL), baby boom (BBM), domain of unknown function 679 membrane protein (DMP), and egg cell-specific (ECS) that trigger in vivo haploid embryo production in both the crops and Arabidopsis models have been identified. The discovery of these haploid inducers indicates that haploid embryogenesis is highly related to gamete development, fertilization, and genome stability in ealry embryos. Here, based on recent efforts to identify key players in haploid embryogenesis and to understand its molecular mechanisms, we summarize the different paths to haploid embryogenesis, and we discuss the mechanisms of haploid generation and its potential applications in crop breeding. Although these haploid-inducing factors could assist egg cells in bypassing fertilization to initiate embryogenesis or trigger genome elimination in zygotes after fertilization to form haploid embryos, the fertilization of central cells to form endosperms is a prerequisite step for haploid formation. Deciphering the molecular and cellular mechanisms for haploid embryogenesis, increasing the haploid induction efficiency, and establishing haploid induction systems in other crops are critical for promoting the application of haploid technology in crop breeding, and these should be addressed in further studies. Full article

Baby Boom (BBM) is a key transcription factor that triggers embryogenesis, enhances transformation and regeneration efficiencies, and regulates developmental pathways in plants. Triggering or activating BBM in non-model crops could overcome the bottlenecks in plant breeding. Understanding BBM’s structure is critical for functional characterization and determination of interacting partners and/or ligands. The current in silico study aimed to study BBM’s sequence and conservation across all plant proteomes, predict protein-protein and protein-ligand interactions, and perform molecular docking and molecular dynamics (MD) simulation to specifically determine the binding site amino acid residues. In addition, peptide sequences that interact with BBM have also been predicted, which provide avenues for altered functional interactions and the design of peptide mimetics that can be experimentally validated for their role in tissue culture or transformation media. This novel data could pave the way for the exploitation of BBM’s potential as the master regulator of specialized plant processes such as apomixes, haploid embryogenesis, and CRISPR/Cas9 transgenic development. Full article

Somatic embryogenesis-mediated plant regeneration is essential for the genetic manipulation of agronomically important traits in upland cotton. Genotype specific recalcitrance to regeneration is a primary challenge in deploying genome editing and incorporating useful transgenes into elite cotton germplasm. In this study, transcriptomes of a semi-recalcitrant cotton (Gossypium hirsutum L.) genotype ‘Coker312’ were analyzed at two critical stages of somatic embryogenesis that include non-embryogenic callus (NEC) and embryogenic callus (EC) cells, and the results were compared to a non-recalcitrant genotype ‘Jin668’. We discovered 305 differentially expressed genes in Coker312, whereas, in Jin668, about 6-fold more genes (2155) were differentially expressed. A total of 154 differentially expressed genes were common between the two genotypes. Gene enrichment analysis of the upregulated genes identified functional categories, such as lipid transport, embryo development, regulation of transcription, sugar transport, and vitamin biosynthesis, among others. In Coker312 EC cells, five major transcription factors were highly upregulated: LEAFY COTYLEDON 1 (LEC1), WUS-related homeobox 5 (WOX5), ABSCISIC ACID INSENSITIVE3 (ABI3), FUSCA3 (FUS3), and WRKY2. In Jin668, LEC1, BABY BOOM (BBM), FUS3, and AGAMOUS-LIKE15 (AGL15) were highly expressed in EC cells. We also found that gene expression of these embryogenesis genes was typically higher in Jin668 when compared to Coker312. We conclude that significant differences in the expression of the above genes between Coker312 and Jin668 may be a critical factor affecting the regenerative ability of these genotypes. Full article

Somatic embryogenesis is a plant regeneration method commonly used in tissue culture. Its molecular mechanisms are well-known in model plants such as Arabidopsis thaliana L. LEAFY COTYLEDON1 (LEC1), LEAFY COTYLEDON2 (LEC2), FUSCA3 (FUS3), ABSCISIC ACID INSENSITIVE3 (ABI3), and BABYBOOM (BBM) genes are considered master regulators in the induction, growth, and maturation of somatic embryos. However, the study of these transcription factors in fruit crops with high agronomic and economic value such as cultivated strawberry (Fragaria × ananassa Duch.) and other Rosaceae species is scarce. The purpose of this study was the in silico characterization of LEC1, ABI3, FUS3, LEC2, and BBM(LAFL-B) genes from F. × ananassa genome and the study of the evolutionary relationships within the Rosaceae family. Synteny analyses and molecular evolutionary rates were performed to analyze the evolution of each transcription factor within the Rosaceae family. Synteny was conserved between F. × ananassa and other Rosaceae genomes, and paralogous genes were selected through negative selection. Additionally, the exon–intron organization and multiple alignments showed that gene structure and DNA-binding domains were conserved in F. × ananassa transcription factors. Finally, phylogenetic trees showed close evolutionary relationships between F. × ananassa and its orthologous proteins in the Rosoideae subfamily. Overall, this research revealed novel insights in the LAFL-B network in F. × ananassa and other species of the Rosaceae family. These results provide useful in silico information and new resources for the establishment of more efficient propagation systems or the study of ploidy effects on somatic embryogenesis. Full article

Auxin contributes to almost every aspect of plant development and metabolism as well as the transport and signalling of auxin-shaped plant growth and morphogenesis in response to endo- and exogenous signals including stress conditions. Consistently with the common belief that auxin is a central trigger of developmental changes in plants, the auxin treatment of explants was reported to be an indispensable inducer of somatic embryogenesis (SE) in a large number of plant species. Treating in vitro-cultured tissue with auxins (primarily 2,4-dichlorophenoxyacetic acid, which is a synthetic auxin-like plant growth regulator) results in the extensive reprogramming of the somatic cell transcriptome, which involves the modulation of numerous SE-associated transcription factor genes (TFs). A number of SE-modulated TFs that control auxin metabolism and signalling have been identified, and conversely, the regulators of the auxin-signalling pathway seem to control the SE-involved TFs. In turn, the different expression of the genes encoding the core components of the auxin-signalling pathway, the AUXIN/INDOLE-3-ACETIC ACIDs (Aux/IAAs) and AUXIN RESPONSE FACTORs (ARFs), was demonstrated to accompany SE induction. Thus, the extensive crosstalk between the hormones, in particular, auxin and the TFs, was revealed to play a central role in the SE-regulatory network. Accordingly, LEAFY COTYLEDON (LEC1 and LEC2), BABY BOOM (BBM), AGAMOUS-LIKE15 (AGL15) and WUSCHEL (WUS) were found to constitute the central part of the complex regulatory network that directs the somatic plant cell towards embryogenic development in response to auxin. The revealing picture shows a high degree of complexity of the regulatory relationships between the TFs of the SE-regulatory network, which involve direct and indirect interactions and regulatory feedback loops. This review examines the recent advances in studies on the auxin-controlled genetic network, which is involved in the mechanism of SE induction and focuses on the complex regulatory relationships between the down- and up-stream targets of the SE-regulatory TFs. In particular, the outcomes from investigations on Arabidopsis, which became a model plant in research on genetic control of SE, are presented. Full article

Effective regeneration of callus tissue into embryos and then into whole plants is essential for plant biotechnology. The embryonic potential is often low and can further decrease with time in culture, which limits the utilisation of calli for transformation procedures and in vitro propagation. In this study, we show that the loss of embryogenic potential in callus cultures of Brachypodium distachyon is progressive over time. Flow cytometry analyses indicated endoploidy levels increased in 60- and 90-day-old calli with effective loss of the 2C DNA content peak in the latter. Analysis of indolic compounds content revealed a decrease in 60- and 90-day-old calli compared to either freshly isolated explants or 30-day-old calli. Immunohistochemical analysis revealed a decrease in arabinogalactan proteins (AGP) signal with the time of culture, but extensin (EXT) epitopes either increased (JIM12 epitopes) or decreased (JIM11 epitopes). The transcript accumulation levels of AGPs and EXTs confirmed these results, with most of AGP and EXT transcripts gradually decreasing. Some chimeric EXT transcripts significantly increased on the 30th day of culture, perhaps because of an increased embryogenic potential. Selected somatic embryogenesis-related genes and cyclins demonstrated a gradual decrease of transcript accumulation for YUCCA (YUC), AINTEGUMENTA-LIKE (AIL), BABY BOOM (BBM), and CLAVATA (CLV3) genes, as well as for most of the cyclins, starting from the 30th day of culture. Notably, WUSCHEL (WUS) transcript was detectable only on the 30th and 60th day and was not detectable in the zygotic embryos and in 90-day-old calli. Full article