A comparative study of characteristics in diploid and tetraploid Anoectochilus roxburghii.

Artificial induction of polyploidy is an efficient technique for improving biological properties and developing new varieties of many plants. In this study, we analyzed and compared differences in characteristics (morphological and biological) of diploid and tetraploid Anoectochilus roxburghii plants. We found significant differences between tetraploid plants and their diploid counterparts. The tetraploid plants exhibited dwarfing and stockiness. They were also bigger and had more voluminous roots and larger stomata than the diploid plants. Moreover, the biochemical analyses showed that the contents of some amino acids and minerals elements were significantly higher in tetraploid plants. The chlorophyll content of the leaves exhibited no definitive changes, but the photosynthetic performance was higher in the tetraploid plants. In addition, contents of major bioactive compounds, such as kinsenoside and some flavonoids, were enhanced in tetraploids. This is the first detailed analysis of characteristics in diploid and tetraploid A. roxburghii plants. The results may facilitate breeding programs with the species.

Chromosome-level assembly of the Neolamarckia cadamba genome provides insights into the evolution of cadambine biosynthesis.

Neolamarckia cadamba (Roxb.), a close relative of Coffea canephora and Ophiorrhiza pumila, is an important traditional medicine in Southeast Asia. Three major glycosidic monoterpenoid indole alkaloids (MIAs), cadambine and its derivatives 3ß-isodihydrocadambine and 3ß-dihydrocadambine, accumulate in the bark and leaves, and exhibit antimalarial, antiproliferative, antioxidant, anticancer and anti-inflammatory activities. Here, we report a chromosome-scale N. cadamba genome, with 744.5 Mb assembled into 22 pseudochromosomes with contig N50 and scaffold N50 of 824.14 Kb and 29.20 Mb, respectively. Comparative genomic analysis of N. cadamba with Co. canephora revealed that N. cadamba underwent a relatively recent whole-genome duplication (WGD) event after diverging from Co. canephora, which contributed to the evolution of the MIA biosynthetic pathway. We determined the key intermediates of the cadambine biosynthetic pathway and further showed that NcSTR1 catalyzed the synthesis of strictosidine in N. cadamba. A new component, epoxystrictosidine (C27H34N2O10, m/z 547.2285), was identified in the cadambine biosynthetic pathway. Combining genome-wide association study (GWAS), population analysis, multi-omics analysis and metabolic gene cluster prediction, this study will shed light on the evolution of MIA biosynthetic pathway genes. This N. cadamba reference sequence will accelerate the understanding of the evolutionary history of specific metabolic pathways and facilitate the development of tools for enhancing bioactive productivity by metabolic engineering in microbes or by molecular breeding in plants.