Porphyra umbilicalis (laver) belongs to an ancient group of red algae (Bangiophyceae), is harvested for human food, and thrives in the harsh conditions of the upper intertidal zone. Here we present the 87.7-Mbp haploid Porphyra genome (65.8% G + C content, 13,125 gene loci) and elucidate traits that inform our understanding of the biology of red algae as one of the few multicellular eukaryotic lineages. Novel features of the Porphyra genome shared by other red algae relate to the cytoskeleton, calcium signaling, the cell cycle, and stress-tolerance mechanisms including photoprotection. Cytoskeletal motor proteins in Porphyra are restricted to a small set of kinesins that appear to be the only universal cytoskeletal motors within the red algae. Dynein motors are absent, and most red algae, including Porphyra, lack myosin. This surprisingly minimal cytoskeleton offers a potential explanation for why red algal cells and multicellular structures are more limited in size than in most multicellular lineages. Additional discoveries further relating to the stress tolerance of bangiophytes include ancestral enzymes for sulfation of the hydrophilic galactan-rich cell wall, evidence for mannan synthesis that originated before the divergence of green and red algae, and a high capacity for nutrient uptake. Our analyses provide a comprehensive understanding of the red algae, which are both commercially important and have played a major role in the evolution of other algal groups through secondary endosymbioses.cytoskeleton | calcium-signaling | carbohydrate-active enzymes | stress tolerance | vitamin B 12T he red algae are one of the founding groups of photosynthetic eukaryotes (Archaeplastida) and among the few multicellular lineages within Eukarya. A red algal plastid, acquired through secondary endosymbiosis, supports carbon fixation, fatty acid synthesis, and other metabolic needs in many other algal groups in ways that are consequential. For example, diatoms and haptophytes have strong biogeochemical effects; apicomplexans cause human disease (e.g., malaria); and dinoflagellates include both coral symbionts and toxin-producing "red tides" (1). The evolutionary processes that produced the Archaeplastida and secondary algal lineages remain under investigation (2-5), but it is clear that both nuclear and plastid genes from the ancestral red algae have contributed dramatically to broader eukaryotic evolution and diversity. Consequently, the imprint of red algal metabolism on the Earth's climate system, aquatic foodwebs, and

SummaryThe use of quantitative disease resistance (QDR) is a promising strategy for promoting durable resistance to plant pathogens, but genes involved in QDR are largely unknown. To identify genetic components and accelerate improvement of QDR in legumes to the root pathogen Aphanomyces euteiches, we took advantage of both the recently generated massive genomic data for Medicago truncatula and natural variation of this model legume.A high-density (%5.1 million single nucleotide polymorphisms (SNPs)) genome-wide association study (GWAS) was performed with both in vitro and glasshouse phenotyping data collected for 179 lines.GWAS identified several candidate genes and pinpointed two independent major loci on the top of chromosome 3 that were detected in both phenotyping methods. Candidate SNPs in the most significant locus (r 2 A = 23%) were in the promoter and coding regions of an F-box protein coding gene. Subsequent qRT-PCR and bioinformatic analyses performed on 20 lines demonstrated that resistance is associated with mutations directly affecting the interaction domain of the F-box protein rather than gene expression.These results refine the position of previously identified QTL to specific candidate genes, suggest potential molecular mechanisms, and identify new loci explaining QDR against A. euteiches.

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