Genome-Wide Identification of the VQ Protein Gene Family of Tobacco (Nicotiana tabacum L.) and Analysis of Its Expression in Response to Phytohormones and Abiotic and Biotic Stresses

VQ motif-containing proteins (VQ proteins) are transcriptional regulators that work independently or in combination with other transcription factors (TFs) to control plant growth and development and responses to biotic and abiotic stresses. VQ proteins contain a conserved FxxhVQxhTG amino acid motif that is the main element of its interaction with WRKY TFs. We identified 59 members of the tobacco (Nicotiana tabacum L.) NtVQ gene family by in silico analysis and examined their differential expression in response to phytohormonal treatments and following exposure to biotic and abiotic stressors. NtVQ proteins clustered into eight groups based upon their amino acid sequence and presence of various conserved domains. Groups II, IV, V, VI, and VIII contained the largest proportion of NtVQ gene family members differentially expressed in response to one or more phytohormone, and NtVQ proteins with similar domain structures had similar patterns of response to different phytohormones. NtVQ genes differentially expressed in response to temperature alterations and mechanical wounding were also identified. Over half of the NtVQ genes were significantly induced in response to Ralstonia solanacearum infection. This first comprehensive characterization of the NtVQ genes in tobacco lays the foundation for further studies of the NtVQ-mediated regulatory network in plant growth, developmental, and stress-related processes.