**Xiangshu Dong 1,\*, Yuan Jiang <sup>1</sup> and Yoonkang Hur 2,\***


Received: 28 February 2019; Accepted: 1 April 2019; Published: 3 April 2019

**Abstract:** Glycoside hydrolase family 1 (GH1) β-glucosidases (BGLUs) are encoded by a large number of genes, and are involved in many developmental processes and stress responses in plants. Due to their importance in plant growth and development, genome-wide analyses have been conducted in model plants (*Arabidopsis* and rice) and maize, but not in *Brassica* species, which are important vegetable crops. In this study, we systematically analyzed *B. rapa BGLU*s (*BrBGLU*s), and demonstrated the involvement of several genes in pollen development. Sixty-four *BrBGLU*s were identified in *Brassica* databases, which were anchored onto 10 chromosomes, with 10 tandem duplications. Phylogenetic analysis revealed that 64 genes were classified into 10 subgroups, and each subgroup had relatively conserved intron/exon structures. Clustering with *Arabidopsis* BGLUs (AtBGLUs) facilitated the identification of several important subgroups for flavonoid metabolism, the production of glucosinolates, the regulation of abscisic acid (ABA) levels, and other defense-related compounds. At least six BrBGLUs might be involved in pollen development. The expression of *BrBGLU10*/*AtBGLU20*, the analysis of co-expressed genes, and the examination of knocked down *Arabidopsis* plants strongly suggests that *BrBGLU10*/*AtBGLU20* has an indispensable function in pollen development. The results that are obtained from this study may provide valuable information for the further understanding of β-glucosidase function and *Brassica* breeding, for nutraceuticals-rich *Brassica* crops.

**Keywords:** β-glucosidase; *Brassica rapa*; BrBGLU10; pollen development; co-expression analysis
