**1. Introduction**

DNA binding with one finger (Dof) transcription factors (TFs) are a family of plant-specific transcription factors. The proteins generally contain 50–52 highly conserved amino acids, including a C2C2-type zinc-finger motif at the N-terminal end [1]. Dof transcription factors have been shown to be widely distributed in the plant kingdom. The cDNA sequence of Dof was first obtained from *Zea mays* [2]. Since then, many Dofs have been cloned from various plant species [3–5]. In previous studies, it is suggested that Dof proteins are involved in the regulation of a variety of biological processes, including seed germination, floral organ abscission, hormone signaling, and cell cycles. In *Arabidopsis*, *DAG1* and *DAG2* can promote seed germination [6,7], *DOF6* acts as a negative regulator of seed germination and interacts with TCP14 [8], and *AtDOF4.7* participates in the transcriptional regulation of floral organ abscission via an effect on cell wall hydrolase gene expression [9]. In addition, some Dof genes (*AtDof2.4*, *AtDof5.8*, and *AtDof5.6*/*HCA2*) are expressed in the early development of vascular cells [10]. In rice, *OsDof3* is involved in gibberellin-regulated expression [11]. Moreover, Dof TFs such as maize *Dof1* and *Dof2* are also involved in the control of carbon and nitrogen metabolism

through the regulation of phosphoenolpyruvate carboxykinase (PECPK), glutamine synthase (GS), and glutamate synthase (GLU) [7,12–16].

Genetic and molecular studies have suggested that Dof transcription factors participate in different stresses, light responsiveness, and flowering regulation. In *Brachypodium distachyon*, *BdCBF1*, *BdCBF2*, and *BdCBF3* contribute to cold, drought, and salt stresses by regulating downstream targets such as DEHYDRIN5.1 (*Dhn5.1*) and *COR* genes [17]. Overexpressing *SlCDF3* shows increased transgenic Arabidopsis drought and salt tolerance [18]. In Chinese cabbage, most *BraDof* genes are induced by cold, heat, high salinity, and drought stresses [19]. Moreover, Dof proteins are involved in photoperiod flowering. In Arabidopsis, cycling Dof factor-1 (CDF1) binds to the *COSTANS* (*CO*) and *FLOWERING LOCUS T* (*FT*) promoter regions to block transactivation of these two flowering genes, whereas this inhibition could be released based on the GIGANTEA-FLAVIN-BINDING, KELCH REPEAT, F-BOX1(GI-FKF1) complex-mediated degradation of CDF1 under long-day (LD) conditions [20]. In addition, *CDF2*, *CDF3*, and *CDF5* repress flowering of Arabidopsis by decreasing the mRNA level of *CO* [21]. In rice, overexpressing *OsDof12* promotes early flowering under LD conditions by upregulating the expression of *Hd3a* and *OsMADS14* [22]. Although a large number of Dofs have been extensively studied in annual plants [23,24], the knowledge of Dofs in moso bamboo is limited.

Moso bamboo (*Phyllostachys edulis*) is a perennial plant characterized by a long vegetative stage that flowers synchronously followed by widespread death [25]. In this case, studying the mechanism of moso bamboo flowering time is very important and challenging, and it is quite difficult to determine the key regulatory gene. Moreover, the growth of moso bamboo in the wild is severely threatened by various environmental conditions such as drought, salinity and cold, which severely limit the growth and distribution of moso bamboo and affect the yield and quality of winter shoots, as well as new bamboo yield in the following year and the yield of wood harvesting of the subsequent years [26–28]. In addition, recent research on Dofs is mainly in annual plants, and is limited in perennials. Therefore, researching the role of Dofs in moso bamboo is necessary, especially in terms of abiotic stress and flowering time. In this study, a Dof gene (*PheDof12-1*) is isolated from moso bamboo, induced by cold, drought, salt, and gibberellin (GA3) stresses. The functional characteristics of *PheDof12-1* are researched for the first time by ectopic expression in Arabidopsis, and transgenic Arabidopsis overexpressing homozygous *PheDof12-1* show early flowering under long-day (LD) conditions, binding to the promoter sequence of PheCOL4 with a strongly diurnal pattern. These results provide new insights into the functions of the Dof transcription factor in the regulation of photoperiod flowering time and abiotic stress in moso bamboo.
