Genome-wide identification of GH3 β-glucosidase members reveals NtBGLC12 improves growth in tobacco plants

Abstract

β-Glucosidase (BGL, EC 3.2.1.21), a glycoside hydrolase, participates in cellulose metabolism and modulates various physiological and biochemical pathways. However, its role in regulating plant growth remains poorly understood. In this study, 19 GH3 β-glucosidase genes (NtBGLCs) were identified in Nicotiana tabacum through genome-wide screening and were phylogenetically classified into two evolutionarily distinct clades. The encoded proteins (418–1254 aa) possess conserved Glyco_hydro_3_C catalytic domains and BglX structural motifs. Transcriptional profiling revealed a significant positive correlation (Pearson’s r = 0.82, P < 0.05) between NtBGLC12 expression levels and leaf biomass 45 days after transplanting. NtBGLC12 exhibited spatiotemporal specificity, with expression remaining stable in stems but increasing progressively in leaves and roots throughout the growth period. Transgenic lines overexpressing NtBGLC12 displayed enhanced growth at the seedling stage (six-true-leaf stage), including a 57.1 % increase in plant height, 51.4 % longer leaves, and 37.7 % wider leaves compared to wild type (WT). Notably, these growth advantages diminished at post-maturation (90 days after transplanting), showing only 6.74 %, 5.30 %, and 6.84 % increases, respectively. Biochemical analyses indicated that NtBGLC12 overexpression elevated β-glucosidase activity by 30 %, increased glucose (33.9 %), soluble sugar (9.87 %), and hemicellulose (11.9 %) content, while reducing cellulose accumulation by 9.05 %. These findings establish NtBGLC12 as a regulator of tobacco growth and implicate its role in cell wall remodeling, offering a novel strategy for enhancing crop productivity.