Genome-wide identification and expression profiling of basic leucine zipper transcription factors following abiotic stresses in potato (Solanum tuberosum L.)

Potato (Solanum tuberosum L.) is an important food crop that is grown and consumed worldwide. The growth and productivity of this crop are severely affected by various abiotic stresses. Basic leucine zipper (bZIP) transcription factors (TFs) in plants are well known for their function during growth and development. However, systematic and in-depth identification and functional characterization of the bZIP gene family of potato is lacking. In the current study, we identified a total of 90 bZIPs (StbZIP) distributed on 12 linkage groups of potato. Based on the previous functional annotation and classification of bZIPs in Arabidopsis, wheat, and rice, a phylogenetic tree of potato bZIPs was constructed and genes were categorized into various functional groups (A to I, S, and U) as previously annotated in Arabidopsis thaliana. Analyses of the transcript sequence (RNA-seq) data led to identifying a total of 18 candidate StbZIPs [four in roots, eight in the tuber, six in mesocarp and endocarp] that were expressed in a tissue-specific manner. Differential expression analysis under the various abiotic conditions (salt, mannitol, water, and heat stress) and treatment with phytohormones (ABA, GA, IAA, and BAP) led to the identification of forty-two [thirteen under salt stress, two under mannitol stress, ten under water stress, and eighteen under heat stress], and eleven [eight and three StbZIPs upon treatment with ABA, and IAA, respectively] candidate StbZIPs, respectively. Using sequence information of candidate StbZIPs, a total of 22 SSR markers were also identified in this study. In conclusion, the genome-wide identification analysis coupled with RNA-Seq expression data led to identifying candidate StbZIPs, which are dysregulated, and may play a pivotal role under various abiotic stress conditions. This study will pave the way for future functional studies using forward and reverse genetics to improve abiotic stress tolerance in potato.