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This Week in PNAS: Oct 24, 2017

In the early, online version of the Proceedings of the National Academy of Sciences, researchers from the University of California, Davis, explore grape domestication and population history using whole-genome sequence data for wild and cultivated Vitis vinifera plants. Based on genome sequences for nine putatively wildplants from the sylvestris subspecies, 18 domesticated grapes from V. vinifera subspecies vinifera, and one representative from the V. rotundifolia subgroup, the team estimated that domesticated and wild grape groups started diverging roughly 22,000 years ago. Domesticated grape population sizes have apparently contracted since that split, the authors say, along with shifts in sex determination strategies and a jump in deleterious mutations in cultivated V. vinifera plants. 

A team from the UK, US, and Mali consider potential malaria vaccine targets by screening a set of antigens produced by the Plasmodium falciparum parasite during the blood stage of infection. The researchers narrowed in on potential targets using a screen relying on antibodies that systematically targeted 29 P. falciparum blood stage antigens alone or in combination, looking at targets that inhibited the parasite's ability to invade red blood cells. After identifying targets that appeared to thwart blood cell invasion by different parasite strains, they went on to assess the potential consequences of targeting antigen combination, tracking parasite invasion with video microscopy. The work "identifies specific antigen combinations for high-priority clinical testing and establishes a generalizable approach that is more likely to produce effective vaccines," the study's authors say.

Researchers from the University of Arizona, the International Rice Research Institute in the Philippines, and other centers take a crack at classifying a clade of columnar cacti that has traditionally been tricky to categorize, in part due to convergent evolution and parallel evolution. The team started its analysis of North American cacti by putting together a high-coverage reference genome assembly and transcriptome for the saguaro cactus Carnegiea gigantea. Together with lower coverage genome sequences for other species from the Sonoran Desert — Pachycereus pringlei, Lophocereus schottii, and Stenocereus thurberi — as well as an outgroup species, the saguaro sequences made it possible to do phylogenetic analyses that highlighted the influence of gene tree-species discordance and species history on amino acid patterns in columnar cacti that might otherwise be attributed to parallel evolution.