Transcriptional profiling and physiological analysis reveal the critical roles of ROS-scavenging system in the Antarctic moss Pohlia nutans under Ultraviolet-B radiation

Abstract

Organisms suffer more harmful ultraviolet radiation in the Antarctica due to the ozone layer destruction. Bryophytes are the dominant flora in the Antarctic continent. However, the molecular mechanism of Antarctic moss adaptation to UV-B radiation remains unclear. In the research, the transcriptional profiling of the Antarctic moss Pohlia nutans under UV-B radiation was conducted by Illumina HiSeq2500 platform. Totally, 72,922 unigenes with N50 length of 1434 bp were generated. Differential expression analysis demonstrated that 581 unigenes were markedly up-regulated and 249 unigenes were significantly down-regulated. The gene clustering analysis showed that these differentially expressed genes (DEGs) includes several transcription factors, photolyases, antioxidant enzymes, and flavonoid biosynthesis-related genes. Further analyses suggested that the content of malondialdehyde (MDA), the activities of several antioxidant enzymes (i.e., catalase, peroxidase, and glutathione reductase) were significantly enhanced upon UV-B treatment. Furthermore, the content of flavonoids and the gene expression levels of their synthesis-related enzymes were also markedly increased when plants were exposed to UV-B light. Therefore, these results suggested that the pathways of antioxidant enzymes, flavonoid synthesis and photolyases were the main defense systems that contributed to the adaption of Pohlia nutans to the enhanced UV-B radiation in Antarctica.