背景回顾：Zygotic embryogenesis is a critical process during seed development in gymnosperms.

提出问题：However, knowledge on the genome-wide transcriptional activation that guides this process in conifers is limited, especially in Picea mongolica. 

主要研究：This tree species is endemic to semiarid habitats of Inner Mongolia in China. To extend what is known about the molecular events underpinning its zygotic embryogenesis, comparative transcriptomic analyses of gene expression in zygotic embryos were performed by RNA sequencing in P. mongolica. 

结果1-整体基因表达变化：Our results showed that most changes in transcript levels occurred in the early embryonic pattering determination and formation of mature embryos.

结果2-重点阐述：Transcripts related to embryogenic competence, cell division pattern, hormones, and stress response genes were identified during embryogenesis.

结果2.1-生长素：Auxin is essential for early embryo patterning and pre-cotyledon embryonic formation. 

结果2.2-脱落酸：However, ABA is a major regulator of embryo maturation. 

结果3-甲基化：Moreover, we found that methylation-related gene expression is associated with activation of early-stage embryos, late embryogenesis abundant proteins, and storage/energy-related genes with late and mature embryos. 

结果4-时期特异性表达基因：Furthermore, network analysis revealed stage-specific and multistage gene expression clusters during embryogenesis. 

结果5-转录因子：WOX, MYB, AP2, and HLH transcription factors seem more relevant to embryogenesis in different stages. 

结论：Our results provide large-scale and comprehensive transcriptome data for embryo development in P. mongolica. These data will lay a foundation for the protection and utilization of P. mongolica resources.

 摘 要 

合子胚胎发育是裸子植物种子发育的一个关键过程。但是，对于针叶树种的合子胚胎发育过程中全基因组范围上的转录激活还所知甚少，尤其是沙地云杉（Picea mongolica）。沙地云杉中国内蒙古地区半干旱生境的特有种。为了进一步了解沙地云杉合子胚胎发育的分子事件，作者通过RNA-seq的方法对沙地云杉不同合子胚胎发育时期进行了基因表达分析。作者发现大多数的基因表达变化发生在早期胚胎模式建成和后期成熟胚胎形成阶段。作者深入鉴定了与胚性能力、细胞分裂模式、激素以及胁迫响应相关基因的表达变化。生长素是早期胚胎模式建成和前子叶胚形成的关键因素。但是，ABA是胚胎成熟的主要调控子。此外，作者还发现甲基化相关基因的表达与早期胚胎的激活、后期胚胎发生富集蛋白以及储存/能量相关基因有关。此外，网络分析揭示了胚胎发生过程中的阶段特异性和多阶段基因表达簇。WOX、MYB、AP2和HLH转录因子似乎与不同阶段的胚胎发生更相关。本文结果为沙地云杉合子胚胎发育提供了全面综合的转录组数据，这些数据为沙地云杉资源的保护和利用奠定了基础。