Jiang Ling, Li Donghao, Jin Lu, Ruan Ying, Shen Wen-Hui, Liu Chunlin
Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, Hunan Agricultural University, Changsha, 410128, China.
Key Laboratory of Education, Department of Hunan Province on Plant Genetics and Molecular Biology, College of Bioscience and Biotechnology, Hunan Agricultural University, Changsha, 410128, China.
Plant J. 2018 May 24. doi: 10.1111/tpj.13978.
Although increasing experimental evidence demonstrates that histone methylations play important roles in Arabidopsis plant growth and development, little information is available regarding Brassica napus. In this study, we characterized two genes encoding homologues of the Arabidopsis histone 3 lysine 36 (H3K36) methyltransferase SDG8, namely, BnaSDG8.A and BnaSDG8.C. Although no duplication of SDG8 homologous genes had been previously reported to occur during the evolution of any sequenced species, a domain-duplication was uncovered in BnaSDG8.C. This duplication led to the identification of a previously unknown NNH domain in the SDG8 homologues, providing a useful reference for future studies and revealing the finer mechanism of SDG8 function. One NNH domain is present in BnaSDG8.A, while two adjacent NNH domains are present in BnaSDG8.C. Reverse transcriptase-quantitative polymerase chain reaction analysis revealed similar patterns but with varied levels of expression of BnaSDG8.A/C in different plant organs/tissues. To directly investigate their function, BnaSDG8.A/C cDNA was ectopically expressed to complement the Arabidopsis mutant. We observed that the expression of either BnaSDG8.A or BnaSDG8.C could rescue the Arabidopsis sdg8 mutant to the wild-type phenotype. Using RNAi and CRISPR/Cas9-mediated gene editing, we obtained BnaSDG8.A/C knockdown and knockout mutants with the early flowering phenotype as compared with the control. Further analysis of two types of the mutants revealed that BnaSDG8.A/C are required for H3K36 m2/3 deposition and prevent the floral transition of B. napus by directly enhancing the H3K36 m2/3 levels at the BnaFLC chromatin loci. This observation on the floral transition by epigenetic modification in B. napus provides useful information for breeding early-flowering varieties.
尽管越来越多的实验证据表明组蛋白甲基化在拟南芥的植物生长和发育中发挥重要作用，但关于甘蓝型油菜的相关信息却很少。在本研究中，我们鉴定了两个编码拟南芥组蛋白3赖氨酸36（H3K36）甲基转移酶SDG8同源物的基因，即BnaSDG8.A和BnaSDG8.C。尽管先前没有报道在任何已测序物种的进化过程中发生过SDG8同源基因的复制，但在BnaSDG8.C中发现了一次结构域复制。这种复制导致在SDG8同源物中鉴定出一个以前未知的NNH结构域，为未来的研究提供了有用的参考，并揭示了SDG8功能的更精细机制。BnaSDG8.A中存在一个NNH结构域，而BnaSDG8.C中存在两个相邻的NNH结构域。逆转录定量聚合酶链反应分析揭示了相似的模式，但BnaSDG8.A/C在不同植物器官/组织中的表达水平有所不同。为了直接研究它们的功能，异位表达BnaSDG8.A/C cDNA以互补拟南芥突变体。我们观察到BnaSDG8.A或BnaSDG8.C的表达都可以将拟南芥sdg8突变体拯救为野生型表型。使用RNA干扰和CRISPR/Cas9介导的基因编辑，我们获得了与对照相比具有早花表型的BnaSDG8.A/C基因敲低和敲除突变体。对这两种突变体的进一步分析表明，BnaSDG8.A/C是H3K36 m2/3沉积所必需的，并且通过直接提高BnaFLC染色质位点的H3K36 m2/3水平来阻止甘蓝型油菜的花期转变。这种关于甘蓝型油菜通过表观遗传修饰进行花期转变的观察为培育早花品种提供了有用的信息。
