Genome-Wide Identification of the BBX Gene Family: StBBX17 Positively Regulates Cold Tolerance in Potato

Potato is an important crop in the world and is rich in various nutrients. Common tetraploid potato is not tolerant of low temperatures and frost. Low-temperature stress severely affects the growth above-ground and the yield underground in potato. The BBX genes play an important role in the plant response to low-temperature stress. However, the molecular mechanism underlying the potato StBBX genes involved in cold stress response remains unclear. In the present study, 30 StBBX genes were identified in potato and divided into five groups. A total of 10 motifs and 10 cis-acting elements were obtained in all BBX proteins. All StBBX genes contained light responsive elements in the promoter, of which nine StBBX genes harbored low-temperature responsive elements. In total, 15 pairs of StBBX genes were identified in duplicated genomic regions. The gene expression patterns of all StBBXs were assessed in different tissues by transcriptome data. The qRT-PCR analysis indicated that six StBBX genes were significantly induced in response to cold stress. Subcellular localization suggested that the StBBX17 protein was localized in the nucleus. Compared with wild type (WT), the cold tolerance in StBBX17 overexpression lines was dramatically increased. After cold treatment, the StBBX17 overexpression lines displayed a less injured area of leaves and lower electrolyte leakage compared with the WT plants, demonstrating StBBX17 positively regulated cold tolerances in potato. These results indicate that StBBX genes have important functions under cold stress, providing a theoretical reference for the breeding of cold-resistant potato.