Overexpression of a garlic nuclear factor Y (NF-Y) B gene, AsNF-YB3, affects seed germination and plant growth in transgenic tobacco

Nuclear factor Y (NF-Y) is a ubiquitous transcription factor found in many eukaryotic organisms. NF-Y consists of three distinct subunits, namely, NF-YA, NF-YB, and NF-YC. In this study, a NF-YB gene, AsNF-YB3, containing the full-length coding region was isolated from garlic. A sequence alignment and phylogenetic analysis showed that AsNF-YB3 clustered with TaNF-YB2 and AtNF-YB3. AsNF-YB3 was expressed in various organs, including the roots, cloves and leaves. A real-time RT-PCR analysis revealed that GA(3), ABA and MeJA treatment upregulated the expression of AsNF-YB3 transcript. Overexpressing AsNF-YB3 in tobacco plants significantly accelerated germination compared to the wild type. Moreover, the total soluble sugar, fructose and sucrose levels were significantly higher in transgenic tobacco lines that constitutively overexpressed AsNF-YB3, suggesting that AsNF-YB3 might be involved in carbohydrate metabolism. Transgenic tobacco plants that overexpressed AsNF-YB3 displayed enhanced root elongation and shoot growth. The overexpression of AsNF-YB3 also strongly promoted early flowering in tobacco. The results of this study in tobacco suggest that garlic AsNF-YB3 likely plays an important role as a plant growth regulator.