Whole-genome sequencing highlights conservative genomic strategies of a stress-tolerant, long-lived scleractinian coral, Porites australiensis Vaughan, 1918

Massive corals of the genus Porites, common, keystone reef builders in the Indo-Pacific Ocean, are distinguished by their relative stress tolerance and longevity. In order to identify genetic bases of these attributes, we sequenced the complete genome of a massive coral, Porites australiensis. We developed a genome assembly and gene models of comparable quality to those of other coral genomes. Proteome analysis identified sixty Porites skeletal matrix protein genes, all of which show significant similarities to genes from other corals and even to those from a sea anemone, which has no skeleton. Nonetheless, 30% of its skeletal matrix proteins were unique to Porites, and were not present in the skeletons of other corals. Comparative genomic analyses showed that genes widely conserved among other organisms are selectively expanded in Porites. Specifically, comparisons of transcriptomic responses of P. australiensis and Acropora digitifera, a stress-sensitive coral, reveal significant differences in regard to genes that respond to increased water temperature, and some of the genes expanded exclusively in Porites may account for the different thermal tolerances of these corals. Taken together, widely shared genes may have given rise to unique biological characteristics of Porites, massive skeletons and stress tolerance.

Whole-genome sequencing of Acer catalpifolium reveals evolutionary history of endangered species

Acer catalpifolium is an endangered species restricted to remote localities of West China. Understanding the genomic content and evolution of A. catalpifolium is essential to conservation efforts of this rare and ecologically valuable plant. Here, we report a high-quality genome of A. catalpifolium consisting of ∼654 Mbps and ∼35,132 protein-coding genes. We detected 969 positively-selected genes in two Acer genomes compared with four other eudicots, 65 of which were transcription factors. We hypothesize that these positively-selected mutations in transcription factors might affect their function and thus contribute to A. catalpifolium’s decline-type population. We also identified 179 significantly expanded gene families compared to 12 other eudicots, some of which are involved in stress responses, such as the FRS-FRF family. We inferred that A. catalpifolium has experienced gene family expansions to cope with environmental stress in its evolutionary history. Finally, 109 candidate genes encoding key enzymes in the lignin biosynthesis pathway were identified in A. catalpifolium; of particular note were the large range and high copy number of cinnamyl alcohol dehydrogenase genes. The chromosome-level genome of A. catalpifolium presented here may serve as a fundamental genomic resource for better understanding endangered Acer species, informing future conservation efforts.