BcLhcb2.1, a Light-harvesting chlorophyll a/b-binding protein from Wucai, plays a positive regulatory role in the response to Abiotic Stress

• In this study, 27 Lhcb gene family members were identified in B. rapa . • Through transcriptome data analysis and RT-qPCR, we identified a crucial gene, BcLhcb2.1 , localized in chloroplasts, that is highly expressed in leaves. • Overexpression of BcLhcb2.1 was associated with enhanced tolerance to cold, salt, and drought stresses in Arabidopsis . Light-harvesting chlorophyll a/b-binding (Lhcb) proteins play key roles in light energy capture and transfer, leaf development, plant growth, and various stress responses. However, their role in Wucai ( Brassica campestris L.) has not yet been studied. In this study, 27 Lhcb genes were identified in Brassica rapa . Chromosomal location analysis revealed that these 27 genes are distributed on nine chromosomes. Subcellular localization analysis indicated that many BrLhcb proteins were present in the chloroplast. The number of exons and introns in BrLhcb family genes was in the range of 1–7 and 0–6, respectively. Cis-acting element analysis of the BrLhcb promoters demonstrated that light-responsive elements were the most common along with elements related to stress and stress-related hormonal signals. In addition, an evolutionary analysis indicated a closer relationship between Lhcb genes of B. rapa and A. thaliana compared with the other three Brassica species. Through transcriptome data analysis and quantitative reverse transcription polymerase chain reaction (RT-qPCR), we identified a crucial gene, BcLhcb2.1 , which is localized in chloroplasts and is highly expressed in leaves. Overexpression of BcLhcb2.1 enhanced cold, salt, and drought tolerance in Arabidopsis. This study provides a theoretical basis for exploring the functions of the BrLhcb gene family and for identifying and screening stress-resistance genes.