A NAC transcription factor, NOR-like1, is a new positive regulator of tomato fruit ripening. Gao Ying,Wei Wei,Zhao Xiaodan,Tan Xiaoli,Fan Zhongqi,Zhang Yiping,Jing Yuan,Meng Lanhuan,Zhu Benzhong,Zhu Hongliang,Chen Jianye,Jiang Cai-Zhong,Grierson Donald,Luo Yunbo,Fu Da-Qi Horticulture research Ripening of the model fruit tomato () is controlled by a transcription factor network including NAC (NAM, ATAF1/2, and CUC2) domain proteins such as No-ripening (NOR), SlNAC1, and SlNAC4, but very little is known about the NAC targets or how they regulate ripening. Here, we conducted a systematic search of fruit-expressed NAC genes and showed that silencing (Solyc07g063420) using virus-induced gene silencing (VIGS) inhibited specific aspects of ripening. Ripening initiation was delayed by 14 days when NOR-like1 function was inactivated by CRISPR/Cas9 and fruits showed obviously reduced ethylene production, retarded softening and chlorophyll loss, and reduced lycopene accumulation. RNA-sequencing profiling and gene promoter analysis suggested that genes involved in ethylene biosynthesis (, ), color formation (, ), and cell wall metabolism (, , and ) are direct targets of NOR-like1. Electrophoretic mobility shift assays (EMSA), chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR), and dual-luciferase reporter assay (DLR) confirmed that NOR-like1 bound to the promoters of these genes both in vitro and in vivo, and activated their expression. Our findings demonstrate that NOR-like1 is a new positive regulator of tomato fruit ripening, with an important role in the transcriptional regulatory network. 10.1038/s41438-018-0111-5

Re-evaluation of the nor mutation and the role of the NAC-NOR transcription factor in tomato fruit ripening. Gao Ying,Wei Wei,Fan Zhongqi,Zhao Xiaodan,Zhang Yiping,Jing Yuan,Zhu Benzhong,Zhu Hongliang,Shan Wei,Chen Jianye,Grierson Donald,Luo Yunbo,Jemrić Tomislav,Jiang Cai-Zhong,Fu Da-Qi Journal of experimental botany The tomato non-ripening (nor) mutant generates a truncated 186-amino-acid protein (NOR186) and has been demonstrated previously to be a gain-of-function mutant. Here, we provide more evidence to support this view and answer the open question of whether the NAC-NOR gene is important in fruit ripening. Overexpression of NAC-NOR in the nor mutant did not restore the full ripening phenotype. Further analysis showed that the truncated NOR186 protein is located in the nucleus and binds to but does not activate the promoters of 1-aminocyclopropane-1-carboxylic acid synthase2 (SlACS2), geranylgeranyl diphosphate synthase2 (SlGgpps2), and pectate lyase (SlPL), which are involved in ethylene biosynthesis, carotenoid accumulation, and fruit softening, respectively. The activation of the promoters by the wild-type NOR protein can be inhibited by the mutant NOR186 protein. On the other hand, ethylene synthesis, carotenoid accumulation, and fruit softening were significantly inhibited in CR-NOR (CRISPR/Cas9-edited NAC-NOR) fruit compared with the wild-type, but much less severely affected than in the nor mutant, while they were accelerated in OE-NOR (overexpressed NAC-NOR) fruit. These data further indicated that nor is a gain-of-function mutation and NAC-NOR plays a significant role in ripening of wild-type fruit. 10.1093/jxb/eraa131