背景回顾：Lignified stone cell content is a key factor used to evaluate fruit quality, influencing the economic value of pear (Pyrus pyrifolia) fruits. 

提出问题：However, our understanding of the regulatory networks of stone cell formation is limited due to the complex secondary metabolic pathway. 

主要发现：In this study, we used a combination of co-expression network analysis, gene expression profiles, and transcriptome analysis in different pear cultivars with varied stone cell content to identify a hub MYB gene, PbrMYB24. 

结果1-PbrMYB24表达水平：The relative expression of PbrMYB24 in fruit flesh was significantly correlated with the contents of stone cells, lignin, and cellulose. 

结果2-验证系统：We then verified the function of PbrMYB24 in regulating lignin and cellulose formation via genetic transformation in homologous and heterologous systems. We constructed a high-efficiency verification system for lignin and cellulose biosynthesis genes in pear callus. 

结果3-PbrMYB24作用机制：PbrMYB24 transcriptionally activated multiple target genes involved in stone cell formation. On the one hand, PbrMYB24 activated the transcription of lignin and cellulose biosynthesis genes by binding to different cis-elements (AC elements and MYB-binding sites). On the other hand, PbrMYB24 bound directly to the promoters of PbrMYB169 and NAC STONE CELL PROMOTING FACTOR (PbrNSC), activating the gene expression. Moreover, both PbrMYB169 and PbrNSC activated the promoter of PbrMYB24, enhancing gene expression. 

结论：This study improves our understanding of lignin and cellulose synthesis regulation in pear fruits through identifying a regulator and establishing a regulatory network. This knowledge will be useful for reducing the stone cell content in pears via molecular breeding.

木质化的石细胞含量是评价梨果实品质的关键因素，其影响了梨果实的经济价值。然而，由于复杂的次级代谢途径，我们对石细胞形成的调节网络还存在盲区。本文中，作者通过对不同石细胞含量的梨果实进行共表达网络分析、基因表达谱和转录组分析，鉴定到了一个核心MYB基因PbrMYB24。PbrMYB24在果肉中的相对表达与石细胞、木质素和纤维素的含量显著相关。接着，作者通过在同源和异源系统中遗传转化，验证了PbrMYB24调节木质素和纤维素形成的功能。作者利用梨愈伤组织构建了一个用于验证木质素和纤维素生物合成基因的高效验证系统。PbrMYB24转录激活了多个参与石细胞形成的靶基因。一方面，PbrMYB24通过结合不同的顺式调控元件，激活了木质素和纤维素生物合成基因的转录。另一方面，PbrMYB24能够直接结合PbrMYB169和PbrNSC基因的启动子，从而激活其表达水平。此外，PbrMYB169和PbrNSC都能够激活PbrMYB24的启动子，增强PbrMYB24基因的表达。本文的研究通过鉴定调节因子和建立调节网络，增加了我们对于梨果实中木质素和纤维素合成调控的理解。这一发现将有助于通过分子育种降低梨果实中的石细胞含量。

** 吴 俊 **