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Major zygotic genome activation (ZGA) occurs at the late 2‐cell stage and involves the activation of thousands of genes, supporting early embryonic development. The reasons underlying the regulation of ZGA are not clear. Acetylation modifications of histone tails promote transcriptional activation, and the maternal deletion of H4K16ac leads to failure in ZGA. GATAD2B is one of the core subunits of the nucleosome remodelling and histone deacetylation (NuRD) complex. Our research has shown that GATAD2B exhibits specific nucleus localization and high protein expression from the late 2‐cell stage to the 8‐cell stage. This intriguing phenomenon prompted us to investigate the relationship between GATAD2B and the ZGA. We discovered a distinctive pattern of GATAD2B, starting from the late 2‐cell stage with nuclear localization. GATAD2B depletion resulted in defective embryonic development, including increased DNA damage at morula, decreased blastocyst formation rate, and abnormal differentiation of ICM/TE lineages. Consistent with the delay during the cleavage stage, the transcriptome analysis of the 2‐cell embryo revealed inhibition of the cell cycle G2/M phase transition pathway. Furthermore, the GATAD2B proteomic data provided clear evidence of a certain association between GATAD2B and molecules involved in the cell cycle pathway. As hypothesized, GATAD2B‐deficient 2‐cell embryos exhibited abnormalities in ZGA during the maternal‐to‐embryonic transition, with lower expression of the major ZGA marker MERVL. Overall, our results demonstrate that GATAD2B is essential for early embryonic development, in part through facilitating ZGA. [ABSTRACT FROM AUTHOR]

SUMMARY: Plant embryogenic calli (ECs) can undergo somatic embryogenesis to regenerate plants. This process is mediated by regulatory factors, such as transcription factors and specifically expressed genes, but the precise molecular mechanisms underlying somatic embryogenesis at the single‐cell level remain unclear. In this study, we performed high‐resolution single‐cell RNA sequencing analysis to determine the cellular changes in the EC of the woody plant species Dimocarpus longan (longan) and clarify the continuous cell differentiation trajectories at the transcriptome level. The highly heterogeneous cells in the EC were divided into 12 putative clusters (e.g., proliferating, meristematic, vascular, and epidermal cell clusters). We determined cluster‐enriched expression marker genes and found that overexpression of the epidermal cell marker gene GDSL ESTERASE/LIPASE‐1 inhibited the hydrolysis of triacylglycerol. In addition, the stability of autophagy was critical for the somatic embryogenesis of longan. The pseudo‐timeline analysis elucidated the continuous cell differentiation trajectories from early embryonic cell division to vascular and epidermal cell differentiation during the somatic embryogenesis of longan. Moreover, key transcriptional regulators associated with cell fates were revealed. We found that ETHYLENE RESPONSIVE FACTOR 6 was characterized as a heat‐sensitive factor that negatively regulates longan somatic embryogenesis under high‐temperature stress conditions. The results of this study provide new spatiotemporal insights into cell division and differentiation during longan somatic embryogenesis at single‐cell resolution. Significance Statement: Plant embryogenic calli can undergo somatic embryogenesis to regenerate plants. The single‐cell RNA‐seq results described herein provide new spatiotemporal insights into cell division and differentiation in the Dimocarpus longan (longan) embryogenic callus. The generated gene expression map will enable us to investigate how embryonic cells differentiate into vascular and epidermal cells. The results may provide the foundation for future molecular and cellular investigations into the mechanisms mediating longan somatic embryogenesis and zygotic embryogenesis. [ABSTRACT FROM AUTHOR]

BACKGROUND: The regulation of functional metabolites under light by structural genes and regulatory genes is understood but the roles of microRNAs in this pathway have rarely been reported and their regulation network is not yet clear. RESULTS: Blue light was most conducive to promoting the synthesis of some functional metabolites in longan embryonic callus (ECs). In this study, we sequenced three small RNA libraries of constructed longan ECs under different light qualities (dark, blue, and white). A total of 29 and 22 miRNAs were differentially expressed in the dark versus blue (DB) and dark versus white (DW) combinations, respectively. According to Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, most of the differentially expressed miRNA target genes were involved in plant hormone signal transduction, mitogen‐activated protein kinase (MAPK) signaling, biosynthesis of unsaturated fatty acids, and so on. Cytoscape analysis of the target genes of miRNAs indicated that miR396b‐5p and miR5139 had the most target genes in DB. Moreover, this study also found that miR171f_3 targeted DELLA, miR390e targeted BRI1, miR396b‐5p targeted EBF1/2 and EIN3; these miRNAs participated in the blue light signaling network through their target genes and regulated the accumulation of longan functional metabolites. CONCLUSIONS: The results of the study revealed that the expressions of phase‐specific miRNAs vary with the change of functional metabolites in longan ECs. This study provides new insights into the molecular mechanisms that allow light to influence plant metabolism. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]