OsMFT1 inhibits seed germination through modulating abscisic acid signaling and gibberellin biosynthesis under salt stress in rice.

Seed dormancy and germination are regulated by endogenous gene expression as well as hormonal and environmental conditions, such as salinity, which greatly inhibits seed germination. MOTHER OF FT AND TFL1 (MFT), which encodes a phosphatidylethanolamine-binding protein, is a key regulator in seed germination of Arabidopsis thaliana. There are two orthologous genes of AtMFT in rice (Oryza sativa), namely OsMFT1 and OsMFT2. However, the functions of these two genes in regulating rice seed germination under salt stress remain unknown. In this study, we found that seeds of loss-of-function osmft1 mutants germinated faster than wild-type (WT) seeds under salt stress, but this was not the case for loss-of-function osmft2 mutants. Overexpression of OsMFT1 (OsMFT1OE) or OsMFT2 increased the sensitivity to salt stress during seed germination. Transcriptome comparisons of osmft1 vs WT in the absence and presence of salt stress yielded several differentially expressed genes, which were associated with salt stress, plant hormone metabolism, and signaling pathways, such as B-BOX ZINC FINGER 6, Oryza sativa bZIP PROTEIN 8, and GIBBERELLIN (GA) 20-oxidase 1. In addition, the sensitivity of OsMFT1OE seeds to GA and osmft1 seeds to ABA during seed germination increased under salt stress. Overall, our results indicate that ABA and GA metabolism and their signaling pathways are regulated by OsMFT1, modulating seed germination in rice under salt stress.