Genome-wide identification and molecular characterization of Citrus unshiu WRKY transcription factors in Satsuma mandarin: Clues for putative involvement in cell growth, fruit ripening, and stress response

Abstract

WRKY transcription factors, being involved in several biological roles, stimulus signaling, and stress response, could be interesting candidates to prospect, particularly in the Citrus unshiu (Satsuma mandarin) genome. Our approach, mainly based on computational analyses, led to the identification of 51 CiuWRKYs followed by their molecular characterization. Syntenic relationship analysis showed significant bias towards sweet orange and Arabidopsis chromosomes. Analyses of promoter region showed that CiuWRKY1 modulates gene transcription through W-box site targeting. The deduced CiuWRKY1 protein was moderately hydrophobic. A comparative in silico analysis among Arabidopsis thaliana and Citrus sinensis WRKYs allowed us to designate orthologous genes. Lacking available CiuWRKY1 expression data, the expression patterns of these orthologous genes indicated that CiuWRKY1 transcription would be modulated by various environmental and biotic constraints and growth regulator stimuli. Our results suggested that the characterization of the CiuWRKY genes in C. unshiu provides new information that can help characterize the molecular mechanisms underlying stress responses and cellular growth, and that CiuWRKY1 would be an interesting candidate to use in Citrus breeding technologies.