Genome-Wide Characterization and Evolutionary Expansion of Poplar NAC Transcription Factors and Their Tissue-Specific Expression Profiles under Drought.

The NAC (NAM, ATAF1/2 and CUC2) is a large gene family of plant-specific transcription factors that play a pivotal role in various physiological processes and abiotic stresses. Due to the lack of genome-wide characterization, intraspecific and interspecific synteny, and drought-responsive expression pattern of genes in poplar, the functional characterization of drought-related genes have been scarcely reported in species. Here, we identified a total of 170 domain-containing genes in the genome, 169 of which were unevenly distributed on its nineteen chromosomes. These genes were phylogenetically divided into twenty subgroups, some of which exhibited a similar pattern of exon-intron architecture. The synteny and Ka/Ks analysis indicated that the expansion of genes in poplar was mainly due to gene duplication events occurring before and after the divergence of and . Ten ( cv.'Nanlin895') genes were randomly selected and cloned. Their drought-responsive expression profiles showed a tissue-specific pattern. The transcription factor PdNAC013 was verified to be localized in the nucleus. Our research results provide genomic information for the expansion of genes in the poplar genome, and for further characterizing putative poplar genes associated with water-deficit.