State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, China.
Laboratory of Horticultural Science, Nagoya University, Nagoya, Japan.
Plant Sci. 2022 May;318:111211. doi: 10.1016/j.plantsci.2022.111211. Epub 2022 Feb 8.
Light environment is an indispensable factor that regulates multitudinous developmental processes during the whole life cycle of plants, including fruit development. Stone cells which negatively influence pear fruit quality because of their strongly lignified cell wall are also affected by light, however, how light qualities influence lignin biosynthesis in pear remains unclear. Here, the calli of European pear (Pyrus communis L.) treated with different lights were used to explore the changes in phenotype, lignin content, and HO content, coupled with RNA-Seq and quantitative real-time PCR (qRT-PCR) to investigate the possible regulation pathway of light on lignin biosynthesis in stone cells. Results showed that blue light increased the expression of lignin structure genes and promoted lignin accumulation. Besides, four blue light receptors cryptochromes (CRYs) were identified in white pear, named PbCRY1a (Pbr024556.1), PbCRY1b (Pbr001636.3), PbCRY2a (Pbr023037.1), and PbCRY2b (Pbr002655.4). qRT-PCR analysis showed that PbCRY1a is highly expressed in cultivars with a high content of stone cells. Furthermore, the molecular function of PbCRY1a on stone cell formation in pear fruit was demonstrated by genetic transformation of pear calli and Agrobacterium-mediated transient overexpression in pear fruitlets. Co-expression network analyses with RNA-seq data showed that 8 MYB and 5 NAC genes were classified into different co-expression clusters with lignin biosynthesis genes under blue light conditions. These results indicate that CRY-mediated blue-light signal plays an important role in cell wall lignification and promotes the formation of stone cells in pear by regulating downstream genes.
光环境是调节植物整个生命周期中众多发育过程的不可或缺的因素，包括果实发育。石细胞因其强烈木质化的细胞壁而对梨果实品质产生负面影响，也受到光的影响，然而，不同光质如何影响梨木质素生物合成尚不清楚。本研究以欧洲梨（Pyrus communis L.）愈伤组织为材料，探讨不同光质处理对石细胞木质素生物合成的影响，采用 RNA-Seq 和定量实时 PCR（qRT-PCR）技术分析木质素结构基因的表达变化。结果表明，蓝光增加了木质素结构基因的表达，促进了木质素的积累。此外，在白梨中鉴定出 4 个蓝光受体隐花色素（CRYs），命名为 PbCRY1a（Pbr024556.1）、PbCRY1b（Pbr001636.3）、PbCRY2a（Pbr023037.1）和 PbCRY2b（Pbr002655.4）。qRT-PCR 分析表明，PbCRY1a 在石细胞含量高的品种中高度表达。此外，通过梨愈伤组织的遗传转化和梨幼果的瞬时过表达，证明了 PbCRY1a 在梨果实石细胞形成中的分子功能。与 RNA-seq 数据的共表达网络分析表明，8 个 MYB 和 5 个 NAC 基因在蓝光条件下与木质素生物合成基因一起被分类到不同的共表达簇中。这些结果表明，CRY 介导的蓝光信号在细胞壁木质化中起重要作用，并通过调节下游基因促进梨石细胞的形成。
