Background: Crop productivity is challenged by abiotic stresses, among which drought stress is the most common. NF-Y genes, especially NF-YA genes, regulate tolerance to abiotic stress. Results: Soybean NF-Y gene GmNFYA5 was identified to have the highest transcript level among all 21 NF-YA genes in soybean ( Glycine max L.) under drought stress. Drought-induced transcript of GmNFYA5 was suppressed by the ABA synthesis inhibitor naproxen (NAP). GmNFYA5 transcript was detected in various tissues at vegetative and reproductive growth stages with higher levels in roots and leaves than in other tissues, which was consist with the GmNFYA5 promoter:GUS fusion assay. Overexpression of GmNFYA5 in transgenic Arabidopsis plants caused enhanced drought tolerance in seedlings by decreasing stomatal aperture and water loss from leaves. Overexpression and suppression of GmNFYA5 in soybean resulted in increased and decreased drought tolerance, respectively, relative to plants with an empty vector (EV). Transcript levels of ABA-dependent genes ( ABI2 , ABI3 , NCED3 , LEA3 , RD29A , P5CS1 , GmWRKY46 , GmNCED2 and GmbZIP1 ) and ABA-independent genes ( DREB1A , DREB2A , DREB2B , GmDREB1 , GmDREB2 and GmDREB3 ) in transgenic plants overexpressing GmNFYA5 were higher than those of wild-type plants under drought stress; suppression of GmNFYA5 transcript produced opposite results. GmNFYA5 probably regulated the transcript abundance of GmDREB2 and GmbZIP1 by binding to the promoters in vivo. Conclusions: Our results suggested that overexpression of GmNFYA5 improved drought tolerance in soybean via both ABA-dependent and ABA-independent pathways.

Background: The crop productivity is challenged by abiotic stresses, among which drought stress is the most widespread . The NF-Y genes, especially NF-YA genes function in regulating drought tolerance of plants. Results: In this study, a soybean NF-Y gene, GmNFYA5 , was identified with the highest transcript level among all of 21 NF-YA genes in soybean ( Glycine max L.) under drought stress. Transcript of GmNFYA5 induced by drought was suppressed by ABA synthesis inhibitor naproxen (NAP). GmNFYA5 transcript was detected in various tissues at vegetative and reproductive growth stage with higher levels in roots and leaves, which was consist with the GmNFYA5 promoter:GUS fusion assay. Overexpression of GmNFYA5 resulted in increased drought tolerance and ABA sensitivity in transgenic Arabidopsis plants. Additionally, overexpression and suppression of GmNFYA5 in soybean resulted in increased and decreased drought tolerance compared with empty vector (EV) plants respectively. Transcript levels of ABA-dependent and ABA-independent genes in transgenic Arabidopsis and soybean plants overexpressing GmNFYA5 were higher than those of WT and EV plants under drought stress respectively, but the opposite results were detected in soybean plants suppressing GmNFYA5 . Furthermore, GmNFYA5 might regulate the expression abundance of GmDREB2 and GmbZIP1 by binding the promoter in vivo. Conclusions: These results suggest that overexpression of GmNFYA5 can improve drought tolerance via ABA-dependent and ABA-independent pathways in soybean.