Main conclusion: OsNF-YC2 and OsNF-YC4 proteins regulate the photoperiodic flowering response through the modulation of three flowering-time genes (Ehd1, Hd3a, andRFT1) in rice. Plant NUCLEAR FACTOR Y (NF-Y) transcription factors control numerous developmental processes by forming heterotrimeric complexes, but little is known about their roles in flowering in rice. In this study, it is shown that some subunits of OsNF-YB and OsNF-YC interact with each other, and among them, OsNF-YC2 and OsNF-YC4 proteins regulate the photoperiodic flowering response of rice. Protein interaction studies showed that the physical interactions occurred between the three OsNF-YC proteins (OsNF-YC2, OsNF-YC4 and OsNF-YC6) and three OsNF-YB proteins (OsNF-YB8, OsNF-YB10 and OsNF-YB11). Repression and overexpression of the OsNF-YC2 and OsNF-YC4 genes revealed that they act as inhibitors of flowering only under long-day (LD) conditions. Overexpression of OsNF-YC6, however, promoted flowering only under LD conditions, suggesting it could function as a flowering promoter. These phenotypes correlated with the changes in the expression of three rice flowering-time genes [Early heading date 1 (Ehd1), Heading date 3a (Hd3a) and RICE FLOWERING LOCUS T1 (RFT1)]. The diurnal and tissue-specific expression patterns of the subsets of OsNF-YB and OsNF-YC genes were similar to those of CCT domain encoding genes such as OsCO3, Heading date 1 (Hd1) and Ghd7. We propose that OsNF-YC2 and OsNF-YC4 proteins regulate the photoperiodic flowering response by interacting directly with OsNF-YB8, OsNF-YB10 or OsNF-YB11 proteins in rice.
Bibliographical noteFunding Information:
We thank Professors C.D. Han (Gyeongsang National University) and K. Shimamoto (NAIST, Japan) for RNAi vectors. We also thank Prof. C.D. Han for 35S::GFP transgenic rice plants and technical help. We are grateful to Kyung-Sook Lee for preparing transgenic rice lines and the RGRC-NIAS (Japan) and Rural Development Administration (Republic of Korea) for rice cDNA and seeds. This work was supported by grants from the Next-Generation BioGreen 21 Program (PJ007978), Rural Development Administration, Republic of Korea and a Korea University Grant (to J.-K.Kim) and by the BK 21 program (to S.-K.Kim).
© 2015, Springer-Verlag Berlin Heidelberg.
- Flowering time
- NUCLEAR FACTOR Y (NF-Y)
- Photoperiodic flowering
ASJC Scopus subject areas
- Plant Science