The FT/FD-dependent initiation of flowering under long-day conditions in the day-neutral species Nicotiana tabacum originates from the facultative short-day ancestor N. tomentosiformis

First author: Farina A. Beinecke; Affiliations: Fraunhofer Institute for Molecular Biology and Applied Ecology (弗劳恩霍夫分子生物学与应用生态学研究所): Münster, Germany

Corresponding author: Dirk Prüfer

Photoperiod is an important external stimulus governing the precise timing of the floral transition in plants. Members of the FLOWERING LOCUS T (FT)‐like clade of phosphatidylethanolamine‐inding proteins (磷脂酰乙醇胺结合蛋白) induce this developmental process in numerous species by forming regulatory protein complexes with FD‐like bZIP transcription factors. We identified several thus far unknown FT‐like and FD‐like genes in the genus Nicotiana and found that, even in the day‐ eutral (日中性) species N. tabacum, floral initiation requires the photoperiod‐dependent expression of several FT‐like genes. Furthermore, floral promotion under long‐day and short‐day conditions is mediated by an FT‐like protein (NtFT5) which originates from the genome of the paternal, facultative (兼性) short‐day ancestor N. tomentosiformis (绒毛状烟草). In contrast, its ortholog of the maternal long‐day ancestor N. sylvestnis (林烟草) is not present in the genome of N. tabacum cv. SR1. Expression profiling in N. tabacum and its ancestors confirmed the relevance of these FT and FD orthologs in the context of polyploidization. We also found that floral inhibition by tobacco FT‐like proteins is not restricted to short‐day conditions, highlighting the coincident expression of tobacco FT‐like genes encoding floral activators and floral inhibitors. Multicolor bimolecular fluorescence complementation analysis (多色荧光互补技术) revealed the preferential formation of FT/FD complexes that promote rather than inhibit flowering, which in concert with the regulation of NtFT and NtFD expression could explain how floral promotion overcomes floral repression during the floral transition in tobacco.

光周期是一个重要的外部刺激条件，能够精确调控植物的成花转变。在大部分植物物种中，磷脂酰乙醇胺结合蛋白类FT家族成员通过与bZIP类FD转录因子形成调控蛋白复合物诱导该进程。作者在烟草属物种中鉴定了一些目前未知功能的类FT和类FD基因，并且发现即使在日中性植物普通烟草中成花转变也需要某些类FT基因的光周期依赖型表达。此外，在长日照和短日照条件下促进成花是由类FT蛋白NtFT5所介导的，该蛋白源自于其父系、兼性短日照祖先物种绒毛状烟草。相反，其母系祖先长日照林烟草中该蛋白的同源物在普通烟草的基因组中并不存在。普通烟草的表达谱及其祖先物种中的情况确认了这些FT和FD同源基因在多倍化过程中的关联。作者还发现烟草类FT蛋白介导的成花抑制并不局限于短日照条件，表明烟草中编码成花促进和成花抑制的类FT基因有着一致的表达。多色荧光互补试验揭示了在烟草中相对于抑制成花，促进成花的FT/FD复合物会优先合成，这与能够解释烟草成花转变中成花促进效果大于成花抑制的NtFT和NtFD基因表达相一致。

通讯：Dirk Prüfer (https://www.uni-muenster.de/Biologie/Mitarbeiter/Pruefer.html)

doi: https://doi.org/10.1111/tpj.14033

Journal: the plant journal

First Published: 21 July, 2018

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