Abstract

(1) Background:Populus yunnanensisDode (P. yunnanensis) grows in the low-latitude and high-altitude areas of southwest China. In low-latitude and high-altitude areas, plants suffer from the high intensity of UV-B (ultraviolet-b) radiation, and they have a complete regulation system to adapt to the environment of the high UV-B radiation. As natural antioxidants, anthocyanins play an important role in scavenging free radicals.BBX(B-box) genes are involved in anthocyanins biosynthesis. (2) Methods: By exploring the gene structure and motifs ofPyunBBXgenes (genes ofP. yunnanensis BBXfamily) and the evolutionary relationship betweenPyunBBXgenes and other speciesBBXgenes, sixPyunBBXgenes that responded to UV-B and participated in anthocyanins biosynthesis were screened.BBX,with the potential to regulate anthocyanins biosynthesis, was further investigated by anthocyanins content determination and RT-qPCR (real-time quantitative polymerase chain reaction); (3) Results: After 7 days of UV-B treatment, anthocyanins were significantly accumulated, and the expression ofPyunBBX18was up-regulated for 7 days. The expression ofPyunBBX12was inhibited by UV-B treatment. By analyzing the RNA-seq data of leaves and bark ofP. yunnanensis, we found thatPyunBBX18was highly expressed in leaves and young bark; (4) Conclusions: These results showed thatPyunBBX18andPyunBBX12may be involved in the response process of UV-B stress, in whichPyunBBX18may regulate the anthocyanins biosynthesis to resist UV damage.Keywords:BBX;Populus yunnanensis;UV stress;anthocyanins;gene family;B-box