Drought and low temperature‐induced NF‐YA1 activates FT expression to promote citrus flowering

Abstract

Flower induction in adult citrus is mainly regulated by drought and low temperatures. However, the mechanism of FLOWERING LOCUS T regulation of citrus flowering (CiFT) under two flower‐inductive stimuli remains largely unclear. In this study, a citrus transcription factor, nuclear factor YA (CiNF‐YA1), was found to specifically bind to the CiFT promoter by forming a complex with CiNF‐YB2 and CiNF‐YC2 to activate CiFT expression. CiNF‐YA1 was induced in juvenile citrus by low temperature and drought treatments. Overexpression of CiNF‐YA1 increased drought susceptibility in transgenic citrus, whereas suppression of CiNF‐YA1 enhanced drought tolerance in silenced citrus plants. Furthermore, a GOLDEN2−LIKE protein (CiFE) that interacts with CiFT protein was also isolated. Further experimental evidence showed that CiFE binds to the citrus LEAFY (CiLFY) promoter and activates its expression. In addition, the expressions of CiNF‐YA1 and CiFE showed a seasonal increase during the floral induction period and were induced by artificial drought and low‐temperature treatments at which floral induction occurred. These results indicate that CiNF‐YA1 may activate CiFT expression in response to drought and low temperatures by binding to the CiFT promoter. CiFT then forms a complex with CiFE to activate CiLFY, thereby promoting the flowering of adult citrus.

Genome-Wide Identification and Analysis of NF-Y Gene Family Reveal Its Potential Roles in Stress-Resistance in Chrysanthemum

“…Among these, OsGhd8 (OsNF-YB11) delays flowering under long-day (LD) conditions but promotes flowering under short-day (SD) conditions by regulating OsEhd1, OsRFT1, and OsHd3a expression [25]. It was recently found that CiNF-YA1 could specifically bind to the CiFT promoter by forming a complex with CiNF-YB2 and CiNF-YC2 to promote flowering of adult lemon (Citrus limon) under drought and low temperatures [26]. In woody plants, RhNF-YC9 can be inhibited by ethylene to regulate petal expansion in rose (Rosa hybrida) [27].…”

IbNF‐YA1 is a key factor in the storage root development of sweet potato

“…In recent studies, NF‐YA1 is involved in multiple biological processes, including nodule differentiation (Hossain et al., 2016), rhizobial infection (Laporte et al., 2014), nitrogen‐fixing nodule symbioses (Bu et al., 2020), flowering (Zhou et al., 2022), seed germination (Siriwardana et al., 2014), and abiotic stresses (Ma, Li, & Wang, 2015; Ma, Zhu, et al., 2015). Thus far, NF‐YA1 has not been reported to regulate the development of storage roots in sweet potato.…”

The Role of Drought and Temperature Stress in the Regulation of Flowering Time in Annuals and Perennials

“…Notably, drought-induced flowering in citrus was also accompanied by the upregulation of the CiFT expression level [37,90]. Earlier studies have also shown that Citrus latifolia flowering is also induced by drought stress, and that all citrus plant species share this same flowering mechanism [91,92]. Additionally, the perennial woody plant Sapium sebiferum takes 3-5 years to flower normally, but one-year-old seedlings under drought stress flower early, which provides a feasible way to shorten the vegetative growth years of woody plants in genetic research and breeding efforts [36].…”

“…Also, Arabidopsis ABF3 and ABF4 act with NF-YCs to mediate drought-accelerated flowering by regulating SOC1 [95] (Figure 1). In citrus, CiNF-YA1 was also found to promote drought-induced flowering by forming a complex with CiNF-YB2 and CiNF-YC2 to activate CiFT expression, and overexpression of CiNF-YA1 in citrus increased plants drought-sensitivity [92]. It is evident that NF-YAs are likely to be functionally conserved in regulating flowering in annual and perennial plants, with functional diversity resulting from physiological differences in response to stress.…”

“…The increase in flower density under cold stress is associated with upregulation of CiFT expression in citrus buds and leaves. The citrus transcription factor CiNF-YA1 has been reported to control the response process to low-temperature stress by forming a complex with CiNF-YB2 and CiNF-YC2 as an upstream regulator of CiFT [92]. The CiFDα protein produced by FD alternative splicing is induced by low temperature, together with FT and the 14-3-3 proteins, forming a complex that regulates plant flowering [13].…”