Genome-wide identification and expression profile of homeodomain-leucine zipper Class I gene family in Cucumis sativus

• A complete set of 13 HD-Zip I genes were identified in the cucumber genome.
• The cucumber HD-Zip I family contained the smaller number of identified genes compared to other species.
• A group of cucumber HD-Zip I genes responded to one or more abiotic stresses.
• Some CsHDZI genes showed closer relationship with their orthologs than paralogs.

The HD-Zip proteins comprise one of the largest families of transcription factors in plants. HD-Zip genes have been grouped into four different classes: HD-Zip I to IV. In this study, we described the identification and structural characterization of Class I HD-Zip genes in cucumber. A complete set of 13 HD-Zip I genes were identified in the cucumber genome using Blast search tools and phylogeny. The cucumber HD-Zip I family contained a smaller number of identified genes compared to other higher plants such as Arabidopsis and maize due to the absence of recent gene duplication events. Chromosomal location of these genes revealed that they are distributed unevenly across 5 of 7 chromosomes. Tissue-specific expression profiles showed that 13 cucumber HD-Zip I genes were expressed in at least one of the tissues, which suggested that cucumber HD-Zip I genes took part in many cellular processes. The transcript abundance level analysis during abiotic stress conditions (NaCl, ABA and low temperature treatments) identified a group of HD-Zip I genes that responded to one or more treatments.