Genome-wide analysis of genes and the tolerance to drought stress in birch ().

BACKGROUND

DNA binding with one finger (Dof) proteins are plant-specific transcription factors playing vital roles in developmental processes and stress responses in plants. Nevertheless, the characterizations, expression patterns, and functions of the Dof family under drought stress (a key determinant of plant physiology and metabolic homeostasis) in woody plants remain unclear.

METHODS

The birch () genome and plant TFDB database were used to identify gene family members in birch plants. ClustalW2 of BioEdit v7.2.1, MEGA v7.0, ExPASy ProtParam tool, Subloc, TMHMM v2.0, GSDS v2.0, MEME, TBtools, KaKs Calculator v2.0, and PlantCARE were respectively used to align the sequences, build a phylogenetic tree, identify the physicochemical properties, analyze the chromosomal distribution and synteny, and identify the -elements in the promoter regions of the 26 genes. Additionally, the birch seedlings were exposed to PEG6000-simulated drought stress, and the expression patterns of the genes in different tissues were analyzed by qRT-PCR. The histochemical staining and the evaluation of physiological indexes were performed to assess the plant tolerance to drought with transient overexpression of , , and genes. SPSS software and ANOVA were used to conduct all statistical analyses and determine statistically significant differences between results.

RESULTS

A total of 26 genes were identified in birch via whole-genome analysis. The conserved Dof domain with a C(x)2C(x)21C(x)2C zinc finger motif was present in all BpDof proteins. These birch were classified into four groups (A to D) according to the phylogenetic analysis of genes. BpDof proteins within the same group mostly possessed similar motifs, as detected by conserved motif analysis. The exon-intron analysis revealed that the structures of genes differed, indicating probable gene gain and lose during the evolution. The chromosomal distribution and synteny analysis showed that the 26 were unevenly distributed on 14 chromosomes, and seven duplication events among six chromosomes were found. -acting elements were abundant in the promoter regions of the 26 genes. qRT-PCR revealed that the expression of the 26 genes was differentially regulated by drought stress among roots, stems, and leaves. Most genes responded to drought stress, and , , and were significantly up-regulated. Therefore, plants overexpressing these three genes were generated to investigate drought stress tolerance. The , , and overexpressing plants showed promoted reactive oxygen species (ROS) scavenging capabilities and less severe cell damage, suggesting that they conferred enhanced drought tolerance in birch. This study provided an in-depth insight into the structure, evolution, expression, and function of the gene family in plants.