Research articleCloning and characterization of a novel GIGANTEA gene in sweet potato

- We isolated and characterized the novel IbGI gene from sweet potato.
- IbGI mRNA levels showed a robust circadian rhythm during the light-dark transition.
- IbGI was upregulated by heat, drought, and salt and downregulated by cold.
- Overexpressing IbGI in Arabidopsis gi-2 rescued its late flowering phenotype.
- Like AtGI, IbGI is a negative regulator of the salt tolerance response.

The transition from vegetative to reproductive growth, a key event in the lifecycle of a plant, is affected by environmental stresses. The flowering-time regulator GIGANTEA (GI) may be contributing to susceptibility of the regulation of photoperiodic flowering, circadian rhythm control, and abiotic stress resistance in Arabidopsis. However, the role of GI in sweet potato remains unknown. Here, we isolated and characterized a GI gene (IbGI) from sweet potato (Ipomoea batatas [L.] Lam). The IbGI cDNA sequence was isolated based on information from a sweet potato transcriptome database. IbGI mRNA transcript levels showed robust circadian rhythm control during the light-dark transition, and the expression of IbGI was stronger in leaves and roots than in stems. IbGI protein is predominantly localized to the nucleus. IbGI expression was upregulated by high temperature, drought, and salt stress but downregulated by cold stress. Overexpressing IbGI in the Arabidopsis gi-2 mutant background rescued its late flowering phenotype and reduced its salt tolerance. Taken together, these results indicate that IbGI shares functions in regulating flowering, the circadian rhythm, and tolerance to some stresses with other GI orthologs.