Lai Tongfei, Wang Xiaohong, Ye Bishun, Jin Mingfei, Chen Weiwei, Wang Ying, Zhou Yingying, Blanks Andrew M, Gu Mei, Zhang Pengcheng, Zhang Xinlian, Li Chunyang, Wang Huizhong, Liu Yule, Gallusci Philippe, Tör Mahmut, Hong Yiguo
Research Centre for Plant RNA Signaling and Zhejiang Provincial Key Laboratory for Genetic Improvement and Quality Control of Medicinal Plants, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, China.
School of Life Sciences, East China Normal University, Shanghai, China.
J Exp Bot. 2020 May 30;71(10):2995-3011. doi: 10.1093/jxb/eraa067.
SlSPL-CNR, an SBP-box transcription factor (TF) gene residing at the epimutant Colourless non-ripening (Cnr) locus, is involved in tomato ripening. This epimutant provides a unique model to investigate the (epi)genetic basis of fruit ripening. Here we report that SlSPL-CNR is a nucleus-localized protein with a distinct monopartite nuclear localization signal (NLS). It consists of four consecutive residues ' 30KRKR33' at the N-terminus of the protein. Mutation of the NLS abolishes SlSPL-CNR's ability to localize in the nucleus. SlSPL-CNR comprises two zinc-finger motifs (ZFMs) within the C-terminal SBP-box domain. Both ZFMs contribute to zinc-binding activity. SlSPL-CNR can induce cell death in tomato and tobacco, dependent on its nuclear localization. However, the two ZFMs have differential impacts on SlSPL-CNR's induction of severe necrosis or mild necrotic ringspot. NLS and ZFM mutants cannot complement Cnr fruits to ripen. SlSPL-CNR interacts with SlSnRK1. Virus-induced SlSnRK1 silencing leads to reduction in expression of ripening-related genes and inhibits ripening in tomato. We conclude that SlSPL-CNR is a multifunctional protein that consists of a distinct monopartite NLS, binds to zinc, and interacts with SlSnRK1 to affect cell death and tomato fruit ripening.
SlSPL-CNR是一个位于表观突变体无色不催熟（Cnr）位点的SBP-box转录因子（TF）基因，参与番茄成熟过程。这个表观突变体为研究果实成熟的（表观）遗传基础提供了一个独特的模型。在此我们报告，SlSPL-CNR是一种定位于细胞核的蛋白，具有独特的单分型核定位信号（NLS）。它由位于该蛋白N端的四个连续残基“30KRKR33”组成。NLS的突变消除了SlSPL-CNR定位于细胞核的能力。SlSPL-CNR在C端SBP-box结构域内包含两个锌指基序（ZFM）。两个ZFM都有助于锌结合活性。SlSPL-CNR可诱导番茄和烟草中的细胞死亡，这依赖于其核定位。然而，这两个ZFM对SlSPL-CNR诱导严重坏死或轻度坏死环斑有不同影响。NLS和ZFM突变体不能使Cnr果实恢复成熟。SlSPL-CNR与SlSnRK1相互作用。病毒诱导的SlSnRK1沉默导致成熟相关基因的表达降低，并抑制番茄成熟。我们得出结论，SlSPL-CNR是一种多功能蛋白，它由一个独特的单分型NLS组成，能结合锌，并与SlSnRK1相互作用以影响细胞死亡和番茄果实成熟。
