Genome-wide identification, characterization, and expression patterns of the BZR transcription factor family in sugar beet (Beta vulgaris L.)

Abstract

Background: BRASSINAZOLE-RESISTANT (BZR) family genes encode plant-specific transcription factors (TFs) that participate in brassinosteroid signal transduction. BZR TFs have vital roles in plant growth, including cell elongation. However, little is known about BZR genes in sugar beet (Beta vulgaris L.).

Results: Therefore, we performed a genome-wide investigation of BvBZR genes in sugar beet. Through an analysis of the BES1_N conserved domain, six BvBZR gene family members were identified in the sugar beet genome, which clustered into three subgroups according to a phylogenetic analysis. Each clade was well defined by the conserved motifs, implying that close genetic relationships could be identified among the members of each subfamily. According to chromosomal distribution mapping, 2, 1, 1, 1, and 1 genes were located on chromosomes 1, 4, 5, 6, and 8, respectively. The cis-acting elements related to taproot growth were randomly distributed in the promoter sequences of the BvBZR genes. Tissue-specific expression analyses indicated that all BvBZR genes were expressed in all three major tissue types (roots, stems, and leaves), with significantly higher expression in leaves. Subcellular localization analysis revealed that Bv1_fxre and Bv6_nyuw are localized in the nuclei, consistent with the prediction of Wolf PSORT.

Conclusion: These findings offer a basis to predict the functions of BZR genes in sugar beet, and lay a foundation for further research of the biological functions of BZR genes in sugar beet.

Keywords: BZR transcription factor; Expression pattern; Genome-wide analysis; Sugar beet; Taproot development.

Fig. 1

Phylogenetic analysis and the grouping of BZR family

Fig. 2

The distribution of conserved motifs for BZR proteins

Fig. 3

Chromosomal distribution and gene structures of BvBZR genes. a Distribution of the BvBZR genes on Beta vulgaris chromosomes. b Exon-intron structures analyses of BvBZR genes

Fig. 4

Analysis of cis-acting elements in BvBZR gene promotors

Fig. 5

Taproot growth rhythm of sugar beet. The E-type cultivar SD13829 and the Z-type cultivar BS02 were grown in field. a The growth curve of taproot. b The growth rate of taproot. c The sugar content curve of taproot. d The increase rate of sugar content of taproot

Fig. 6

The expression patterns of BvBZR genes. a The clustering anslysis for expression pattern of BvBZR family gene in taproot development. The expression level of BvBZR genes in the taproot of E-type cultivar SD13829 and Z-type cultivar BS02 at 38, 69, 89, 99, 120 and 143 DAE. b The different expression of BvBZR genes in the taproot of E-type cultivar SD13829 compared to that in the taproot of Z-type cultivar BS02 at 38, 69, 89, 99, 120 and 143 DAE

Fig. 7

The analysis of organ specific expression for BvBZR genes

Fig. 8

Response of BvBZR genes to several phytohormones. The seedling age was 69 days. The exogenous GA₃ (80 mg/L), ABA (10 mg/L), IAA (0.5 mg/L) and MeJA (200 μmol/L) were sprayed to the beetroot, the control group was sprayed with water

Fig. 9

Subcellular localization of Bv1_fxre and Bv6_nyuw