Identification and Analysis of the Organization of sHsp Genes in Nicotiana attenuata and Solanum lycopersicum (Solanaceae)

Low-molecular-weight heat shock proteins (sHSPs) play a key role in protecting plants from abiotic stress and are also involved in growth and development processes. In this study, using bioinformatics approaches, a comprehensive analysis of the multigenic sHsp family in members of the Solanaceae family, which includes numerous food, medicinal, and ornamental plant species, was performed. As a result of a genomic screening for two members of this family, Nicotiana attenuata (coyote tobacco), Solanum lycopersicum (tomato), and the model plant Arabidopsis thaliana, 52, 45, and 34 putative sHsp genes were identified, respectively, and their chromosomal localization was determined. All tobacco genes, five tomato genes, and one Arabidopsis gene were identified for the first time. The putative sHSPs belong to 19 classes. They differ in the size of their structural domains and contain targeting signals for various cellular compartments. Most classes formed before the divergence of the phylogenetic lineages of Superrosids and Superasterids and were conserved throughout the further evolution of dicots, while some classes proved to be specific to A. thaliana or members of the Solanaceae family. Several sHsps are characterized by a clustered organization on the chromosomes, which arose through tandem duplications of individual genes during evolution. In the genomes examined, 15 sHsps were identified, encoding two to four alternative transcripts. Analysis of the promoter regions revealed numerous recognition sites for transcription factors associated with the regulation of stress responses, light signaling, phytohormone action, and various processes governing plant growth and development.