Algal genes in aplastidic eukaryotes are not necessarily derived from historical plastids

In photosynthetic eukaryotes, many genes were transferred from plastids or algal endosymbionts to nuclear genomes of host cells. These transferred genes are often considered genetic footprints of plastids. However, genes of algal origin have also been detected in some plastid-lacking eukaryotes, and these genes are often cited as evidence of historical plastids. In this paper, we discuss two recent publications about algal genes in plastid-lacking eukaryotes. Both studies highlight the point that algal genes are not exclusively derived from historical plastids. Instead, the findings show that gene acquisition through feeding activities is a plausible explanation

The scale and evolutionary significance of horizontal gene transfer in the choanoflagellate

Background It is generally agreed that horizontal gene transfer (HGT) is common in phagotrophic protists. However, the overall scale of HGT and the cumulative impact of acquired genes on the evolution of these organisms remain largely unknown. Results Choanoflagellates are phagotrophs and the closest living relatives of animals. In this study, we performed phylogenomic analyses to investigate the scale of HGT and the evolutionary importance of horizontally acquired genes in the choanoflagellate Monosiga brevicollis. Our analyses identified 405 genes that are likely derived from algae and prokaryotes, accounting for approximately 4.4% of the Monosiga nuclear genome. Many of the horizontally acquired genes identified in Monosiga were probably acquired from food sources, rather than by endosymbiotic gene transfer (EGT) from obsolete endosymbionts or plastids. Of 193 genes identified in our analyses with functional information, 84 (43.5%) are involved in carbohydrate or amino acid metabolism, and 45 (23.3%) are transporters and/or involved in response to oxidative, osmotic, antibiotic, or heavy metal stresses. Some identified genes may also participate in biosynthesis of important metabolites such as vitamins C and K12, porphyrins and phospholipids. Conclusions Our results suggest that HGT is frequent in Monosiga brevicollis and might have contributed substantially to its adaptation and evolution. This finding also highlights the importance of HGT in the genome and organismal evolution of phagotrophic eukaryotes

Ancient gene transfer from algae to animals: Mechanisms and evolutionary significance

Background Horizontal gene transfer (HGT) is traditionally considered to be rare in multicellular eukaryotes such as animals. Recently, many genes of miscellaneous algal origins were discovered in choanoflagellates. Considering that choanoflagellates are the existing closest relatives of animals, we speculated that ancient HGT might have occurred in the unicellular ancestor of animals and affected the long-term evolution of animals. Results Through genome screening, phylogenetic and domain analyses, we identified 14 gene families, including 92 genes, in the tunicate Ciona intestinalis that are likely derived from miscellaneous photosynthetic eukaryotes. Almost all of these gene families are distributed in diverse animals, suggesting that they were mostly acquired by the common ancestor of animals. Their miscellaneous origins also suggest that these genes are not derived from a particular algal endosymbiont. In addition, most genes identified in our analyses are functionally related to molecule transport, cellular regulation and methylation signaling, suggesting that the acquisition of these genes might have facilitated the intercellular communication in the ancestral animal. Conclusions Our findings provide additional evidence that algal genes in aplastidic eukaryotes are not exclusively derived from historical plastids and thus important for interpreting the evolution of eukaryotic photosynthesis. Most importantly, our data represent the first evidence that more anciently acquired genes might exist in animals and that ancient HGT events have played an important role in animal evolution

Genome of Crucihimalaya himalaica, a close relative of Arabidopsis, shows ecological adaptation to high altitude

Crucihimalaya himalaica is a close relative of Arabidopsis with typical Qinghai–Tibet Plateau (QTP) distribution. Here, by combining short- and long-read sequencing technologies, we provide a de novo genome sequence of C. himalaica. Our results suggest that the quick uplifting of the QTP coincided with the expansion of repeat elements. Gene families showing dramatic contractions and expansions, as well as genes showing clear signs of natural selection, were likely responsible for C. himalaica’s specific adaptation to the harsh environment of the QTP. We also show that the transition to self-pollination of C. himalaica might have enabled its occupation of the QTP. This study provides insights into how plants might adapt to extreme environmental conditions

Shangrilaia (Brassicaceae), a New Genus from China

Volume: 14Start Page: 271End Page: 27

New insights into the taxonomy of tribe Euclidieae (Brassicaceae), evidence from nrITS sequence data

As currently delimitated, the species-rich mustard tribe Euclidieae DC. (Brassicaceae) comprises 28 genera and 152 species distributed primarily in Asia. To date, no tribe-wide comprehensive phylogenetic analysis has been conducted. In this study, sequence data from the nuclear ribosomal internal transcribed spacer (nrITS) region of 82 species in all 28 genera of Euclidieae were used to test its monophyly and infer inter- and intra-generic relationships within. Phylogenetic analyses revealed that Rhammatophyllum and Sisymbriopsis are embedded within Solms-laubachia s.l., and Solms-laubachia lanuginosa (Eurycarpus lanuginosus) fell outside the tribe. Therefore, Solms-laubachia s.l. as currently recognized is not monophyletic and its generic delimitation needed further study. Besides, our results suggest that the genera Lepidostemon, Neotorularia, and Tetracme are polyphyletic

Sisymbrium linifolium and Sisymbriopsis schugnana (Brassicaceae), two new records from Xinjiang, China

Sisymbrium linifolium and Sisymbriopsis schugnana, previously confined to western North America and Tajikistan, respectively, were discovered in Xinjiang during a recent field trip to this autonomous region of China. The identity of these two species was subsequently confirmed by extensive morphological and molecular studies. The biogeographical significance of these new floristic records is briefly addressed

Sisymbrium linifolium and Sisymbriopsis schugnana (Brassicaceae), two new records from Xinjiang, China

Sisymbrium linifolium and Sisymbriopsis schugnana, previously confined to western North America and Tajikistan, respectively, were discovered in Xinjiang during a recent field trip to this autonomous region of China. The identity of these two species was subsequently confirmed by extensive morphological and molecular studies. The biogeographical significance of these new floristic records is briefly addressed

Sisymbrium linifolium and Sisymbriopsis schugnana (Brassicaceae), two new records from Xinjiang, China

Sisymbrium linifolium and Sisymbriopsis schugnana, previously confined to western North America and Tajikistan, respectively, were discovered in Xinjiang during a recent field trip to this autonomous region of China. The identity of these two species was subsequently confirmed by extensive morphological and molecular studies. The biogeographical significance of these new floristic records is briefly addressed