Molecular cloning and expression analysis of HD-ZIP Ⅳ transcription factor gene NtPDF2 from Nicotiana tabacum

To identify the biological functions of NtPDF2 and its mechanism in regulating trichome development in tobacco, NtPDF2 gene was cloned by homologous cloning strategy. The gene sequence, exon/intron structure, phylogenetic relationship and expression pattern of NtPDF2 were analyzed. The results showed that the full-length CDS sequence of NtPDF2 was 2 199 bp, which encoded 732 amino acids. The putative protein sequences of tobacco PDF2 were highly conserved, especially C-terminal which included three conserved domains (Homeobox domain, START domain and SAD domain) and one conserved LZ (Leucine zipper) motif. The gene structure of NtPDF2 was highly conserved, including 10 exons and 9 introns. Phylogenetic analysis revealed that NtPDF2 was evolved from NsylML1 gene. The expression pattern of NtPDF2 had an obvious spatio-temporal specificity. The transcription level of NtPDF2 significantly decreased under drought, darkness and phosphate starvation, while it did not change obviously under salt stress. Furthermore, GA, ABA, MeJA and topping treatments significantly induced the expression of NtPDF2, which suggested that NtPDF2 might participate in plant responses to various abiotic stresses and phytohormones.