02263nas a2200217 4500008004100000245013700041210006900178520154300247653002501790653002401815653001401839653001101853653001901864653002201883100002001905700001901925700001701944700001701961700001901978856004801997 2017 eng d00aPlastome evolution in the sole hemiparasitic genus laurel dodder (Cassytha) and insights into the plastid phylogenomics of Lauraceae0 aPlastome evolution in the sole hemiparasitic genus laurel dodder3 a

To date, little is known about the evolution of plastid genomes (plastomes) in Lauraceae. As one of the top five largest families in tropical forests, the Lauraceae contain many species that are important ecologically and economically. Lauraceous species also provide wonderfulmaterials to study the evolutionary trajectory in response to parasitism because they contain both nonparasitic and parasitic species. This study compared the plastomes of nine Lauraceous species, including the sole hemiparasitic and herbaceous genus Cassytha (laurel dodder; here represented by Cassytha filiformis).We found differential contractions of the canonical inverted repeat (IR), resulting in two IR types present in Lauraceae. These two IR types reinforce Cryptocaryeae and Neocinnamomum–Perseeae–Laureae as two separate clades. Our data reveal several traits unique to Cas. filiformis, including loss of IRs, loss or pseudogenization of 11 ndh and rpl23 genes, richness of repeats, and accelerated rates of nucleotide substitutions in protein-coding genes. Although Cas. filiformis is low in chlorophyll content, our analysis based on dN/dS ratios suggests that both its plastid house-keeping and photosynthetic genes are under strong selective constraints. Hence, we propose that short generation time and herbaceous lifestyle rather than reduced photosynthetic ability drive the accelerated rates of nucleotide substitutions in Cas. filiformis.

10agenome rearrangement10ahemiparasitic plant10aLauraceae10alaurel10aplastid genome10asubstitution rate1 aWu, Chung-Shien1 aWang, Ting-Jen1 aWu, Chia-Wen1 aWang, Ya-Nan1 aChaw, Shu-Miaw uhttps://lauraceae.myspecies.info/node/20402