Laboratory of Fruit Biology, College of Food Science & Nutritional Engineering, China Agricultural University, Beijing, 100083, China.
Laboratory of Fruit Quality Biology, Zhejiang Provincial Key Laboratory of Horticultural Plant Integrative Biology, Zhejiang University, Zijingang Campus, Hangzhou, 310058, China.
Plant J. 2021 Dec;108(5):1317-1331. doi: 10.1111/tpj.15512. Epub 2021 Nov 2.
Fruit ripening in tomato (Solanum lycopersicum) is the result of selective expression of ripening-related genes, which are regulated by transcription factors (TFs). The NAC (NAM, ATAF1/2, and CUC2) TF family is one of the largest families of plant-specific TFs and members are involved in a variety of plant physiological activities, including fruit ripening. Fruit ripening-associated NAC TFs studied in tomato to date include NAC-NOR (non-ripening), SlNOR-like1 (non-ripening like1), SlNAC1, and SlNAC4. Considering the large number of NAC genes in the tomato genome, there is little information about the possible roles of other NAC members in fruit ripening, and research on their target genes is lacking. In this study, we characterize SlNAM1, a NAC TF, which positively regulates the initiation of tomato fruit ripening via its regulation of ethylene biosynthesis. The onset of fruit ripening in slnam1-deficient mutants created by CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9) technology was delayed, whereas fruit ripening in OE-SlNAM1 lines was accelerated compared with the wild type. The results of RNA-sequencing (RNA-seq) and promoter analysis suggested that SlNAM1 directly binds to the promoters of two key ethylene biosynthesis genes (1-aminocyclopropane-1-carboxylate synthase: SlACS2 and SlACS4) and activates their expression. This hypothesis was confirmed by electrophoretic mobility shift assays and dual-luciferase reporter assay. Our findings provide insights into the mechanisms of ethylene production and enrich understanding of the tomato fruit ripening regulatory network.
番茄（Solanum lycopersicum）果实成熟是成熟相关基因选择性表达的结果，这些基因受转录因子（TFs）调控。NAC（NAM、ATAF1/2 和 CUC2）TF 家族是植物特异性 TF 中最大的家族之一，其成员参与多种植物生理活动，包括果实成熟。迄今为止，在番茄中研究的与果实成熟相关的 NAC TF 包括 NAC-NOR（不成熟）、SlNOR-like1（不类似 1）、SlNAC1 和 SlNAC4。考虑到番茄基因组中 NAC 基因数量众多，关于其他 NAC 成员在果实成熟中可能发挥的作用的信息很少，并且对其靶基因的研究也很少。在这项研究中，我们描述了 SlNAM1，一种 NAC TF，它通过调节乙烯生物合成来正向调节番茄果实成熟的启动。CRISPR/Cas9（成簇规律间隔短回文重复序列和 CRISPR 相关蛋白 9）技术创建的 slnam1 缺陷突变体中果实成熟的开始延迟，而 OE-SlNAM1 系中果实成熟的加速与野生型相比。RNA-seq（RNA-seq）和启动子分析的结果表明，SlNAM1 直接结合到两个关键乙烯生物合成基因（1-氨基环丙烷-1-羧酸合酶：SlACS2 和 SlACS4）的启动子上，并激活它们的表达。这一假设通过电泳迁移率变动分析和双荧光素酶报告基因 assay 得到了证实。我们的研究结果为乙烯产生的机制提供了深入的见解，并丰富了对番茄果实成熟调控网络的理解。
