RICE CENTRORADIALIS 1, a TFL1-like Gene, Responses to Drought Stress and Regulates Rice Flowering Transition

Abstract

Background: The initiation of flowering transition in rice (Oryza sativa) is a complex process regulated by genes and environment. In particular, drought can interfere with flowering; therefore, many plants hasten this process to shorten their life cycle under water scarcity, and this is known as drought-escape response. However, rice has other strategies; for example, drought stress can delay flowering instead of accelerating it. RICE CENTRORADIALIS 1 (RCN1) is a TERMINAL FLOWER-like gene that influences rice flowering transition and spike differentiation. It interacts with 14-3-3 proteins and transcription factor OsFD1 to form a florigen repression complex that suppresses flowering transition in rice.

Results: In this study, we explored the role of RCN1 in the molecular pathway of drought-regulated flowering transition. The rcn1 mutant plants displayed early heading under both normal water and drought stress conditions, and they were more insensitive to drought stress than the wild-type plants. Abscisic acid (ABA) signaling-mediated drought-induced RCN1 is involved in this process.

Conclusions: Thus, RCN1 plays an important role in the process of drought stress inhibiting flowering transition. It may worked by suppressing the protein function rather than transcription of HEADING DATE 3a.

Keywords: Drought; Florigen; Flowering transition; Heading time; RCN1; Rice.

Fig. 1

Expression patterns of RCN1 in rice. Expression of RCN1 RNA in rice (a). RCN1 expression was analyzed by quantitative real-time PCR throughout the growth period. Actin RNA was used as the control. DAS: days after seeding. GUS staining images of pRCN1::GUS:NOS in transgenic rice leaf (b), root (c), stem node (d), basal internodes (e), young panicle (f), and glume (g). The localization of the RCN1-GFP protein was visualized in confocal images of the leaf (h) and root (i) in pRCN1::RCN1-GFP:NOS transgenic rice plants, and the subcellular localization of the RCN1-GFP protein was visualized lateral root cells (j). Bars = 100 μm (for b-c), 1 mm (for d-g)

Fig. 2

Expression levels of RCN1 in the leaves and roots under different PEG6000 treatment concentrations (a and b), different ABA treatment times (c and d), and ABA treatment concentrations (e and f). PEG6000-induced RCN1 levels in the leaves (g) and roots (h) depended on ABA synthesis and protein phosphorylation. ABA-induced RCN1 levels in the leaf (i) and root (j) depended on de novo protein synthesis. CHX: cycloheximide. ABA-induced RCN1 expression levels in the leaf (k) and (l) root depended on protein phosphorylation. Note: Statistical analysis was performed using the Student’s t test; significantly different values at P < 0.05 (*) or P < 0.01 (**) are indicated

Fig. 3

Location of the probes in the genomic DNA of RCN1 (a). OSBZ8 (b) and OsAREB1 (c) were bound to the downstream sequence of RCN1. Note: 50×: 50 times concentration; 200×: 200 times concentration

Fig. 4

OsAREB1- and OSBZ8-induced RCN1 expression. The expression levels of OSBZ8 in Gos2::OSBZ8 (a) and Gos2::OsAREB1 (b) transgenic plants under DEX treatment. Expression levels of RCN1 in Gos2::OSBZ8 (c) and Gos2::OsAREB1 (d) transgenic plants under DEX treatment. DEX: dexamethasone

Fig. 5

Differences in promoters and terminators in pRCN1::GUS:NOS and pRCN1::RCN1-GFP:NOS transgenic plants and wild-type (WT) plants (a). The expression levels of native RCN1 and GUS in the pRCN1::GUS:NOS transgenic plants under ABA treatment (b). The expression levels of native RCN1 and GFP in the pRCN1::RCN1-GFP:NOS transgenic plants under ABA treatment (c)