Murraya paniculata, commonly called orange jessamine in the family Rutaceae, is an important ornamental plant in tropical and subtropical regions which is famous for its strong fragrance. As ornamental plants with strong flower aroma, the flower volatiles of M. paniculata differ from those of Citrus plants in Aurantioideae. However, the molecular basis for the biosynthesis of compounds and the reason for the significant differences in volatiles between Citrus and Murraya are still unknown. In a study published in BMC Biology, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and Kunming Institute of Botany (KIB) report the first chromosome-level reference genome of M. paniculata with a total assembly length of 216.87 Mb of 9 chromosomes and a contig N50 of 18.25 Mb. The researchers conducted comparative analyses with other published Aurantioideae genomes and found that transposon expansion was responsible for the different genome sizes between M. paniculata and the other Aurantioideae species. Obvious differences in transposon contents were detected in the genomes among M. paniculata and other Aurantioideae species, especially in the upstream regions of genes, which may affect metabolites biosynthesis. They then carried out the flower volatiles analysis and transcriptome analysis in M. paniculata and C. maxima at different developmental periods. They newly identified three genes with strong synthetic activity for phenylacetaldehyde in M. paniculata. The expressions of two homologues of these genes in C. maxima may be affected by long terminal repeat (LTR) insertions which led to the lack of phenylacetaldehyde in flowers of C. maxima.
"We presented a high-quality reference genome of M. paniculata, which is the first chromosome-level genome assembly in Murraya plants. Our study provides insights into how transposons contribute to variations in flower volatiles among Murraya and Citrus plants,” said Prof. YANG Yongping of XTBG. Contact YANG Yongping Principal Investigator Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, Yunnan, China E-mail: yangyp@xtbg.ac.cn 
M. paniculata genomic landscape. (Image by YANG Tianyu) |
