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1.
Plant Cell ; 35(8): 3053-3072, 2023 08 02.
Artigo em Inglês | MEDLINE | ID: mdl-37100425

RESUMO

The ketocarotenoid fucoxanthin and its derivatives can absorb blue-green light enriched in marine environments. Fucoxanthin is widely adopted by phytoplankton species as a main light-harvesting pigment, in contrast to land plants that primarily employ chlorophylls. Despite its supreme abundance in the oceans, the last steps of fucoxanthin biosynthesis have remained elusive. Here, we identified the carotenoid isomerase-like protein CRTISO5 as the diatom fucoxanthin synthase that is related to the carotenoid cis-trans isomerase CRTISO from land plants but harbors unexpected enzymatic activity. A crtiso5 knockout mutant in the model diatom Phaeodactylum tricornutum completely lacked fucoxanthin and accumulated the acetylenic carotenoid phaneroxanthin. Recombinant CRTISO5 converted phaneroxanthin into fucoxanthin in vitro by hydrating its carbon-carbon triple bond, instead of functioning as an isomerase. Molecular docking and mutational analyses revealed residues essential for this activity. Furthermore, a photophysiological characterization of the crtiso5 mutant revealed a major structural and functional role of fucoxanthin in photosynthetic pigment-protein complexes of diatoms. As CRTISO5 hydrates an internal alkyne physiologically, the enzyme has unique potential for biocatalytic applications. The discovery of CRTISO5 illustrates how neofunctionalization leads to major diversification events in evolution of photosynthetic mechanisms and the prominent brown coloration of most marine photosynthetic eukaryotes.


Assuntos
Diatomáceas , Xantofilas , Simulação de Acoplamento Molecular , Xantofilas/metabolismo , Carotenoides/metabolismo , Clorofila/metabolismo , Diatomáceas/genética , Diatomáceas/metabolismo
2.
Plant Biotechnol J ; 20(1): 116-128, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-34487631

RESUMO

Achnatherum splendens Trin. (Gramineae) is a constructive species of the arid grassland ecosystem in Northwest China and is a major forage grass. It has good tolerance of salt and drought stress in alkaline habitats. Here, we report its chromosome-level genome, determined through a combination of Illumina HiSeq sequencing, PacBio sequencing and Hi-C technology. The final assembly of the ~1.17 Gb genome sequence had a super-scaffold N50 of 40.3 Mb. A total of 57 374 protein-coding genes were annotated, of which 54 426 (94.5%) genes have functional protein annotations. Approximately 735 Mb (62.37%) of the assembly were identified as repetitive elements, and among these, LTRs (40.53%) constitute the highest proportion, having made a major contribution to the expansion of genome size in A. splendens. Phylogenetic analysis revealed that A. splendens diverged from the Brachypodium distachyon-Hordeum vulgare-Aegilops tauschii subclade around 37 million years ago (Ma) and that a clade comprising these four species diverged from the Phyllostachys edulis clade ~47 Ma. Genomic synteny indicates that A. splendens underwent an additional species-specific whole-genome duplication (WGD) 18-20 Ma, which further promoted an increase in copies of numerous saline-alkali-related gene families in the A. splendens genome. By transcriptomic analysis, we further found that many of these duplicated genes from this extra WGD exhibited distinct functional divergence in response to salt stress. This WGD, therefore, contributed to the strong resistance to salt stress and widespread arid adaptation of A. splendens.


Assuntos
Brachypodium , Tolerância ao Sal , Ecossistema , Pradaria , Anotação de Sequência Molecular , Filogenia , Tolerância ao Sal/genética
3.
BMC Genet ; 20(1): 33, 2019 03 12.
Artigo em Inglês | MEDLINE | ID: mdl-30866795

RESUMO

BACKGROUND: The genus Ostrya (Betulaceae) contains eight species and four of them are distributed in China. However, studies based on limited informative sites of several chloroplast markers failed to resolve interspecific delimitation and relationships among the four Chinese species. In this study, we aimed to use the whole chloroplast genomes to address these two issues. RESULTS: We assembled and annotated 33 complete chloroplast genomes (plastomes) of the four Chinese species, representing 17 populations across most of their geographical distributions. Each species contained samples of several individuals that cover most of geographic distributions of the species. All plastomes are highly conserved in genome structure and gene order, with a total length of 158-159 kb and 122 genes. Phylogenetic analyses of whole plastomes, non-coding regions and protein-coding genes produced almost the same topological relationships. In contrast to the well-delimitated species boundary inferred from the nuclear ITS sequence variations, three of the four species are non-monophyletic in the plastome trees, which is consistent with previous studies based on a few chloroplast markers. CONCLUSIONS: The high incongruence between the ITS and plastome trees may suggest the widespread occurrences of hybrid introgression and incomplete lineage sorting during the divergence of these species. In addition, the plastomes with more informative sites compared with a few chloroplast markers still failed to resolve the phylogenetic relationships of the four species, and further studies involving population genomic data may be needed to better understand their evolutionary histories.


Assuntos
Betulaceae/genética , Genoma de Cloroplastos/genética , DNA de Plantas/genética , Genômica , Filogenia
4.
Nat Commun ; 15(1): 5578, 2024 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-38956103

RESUMO

Diatoms often outnumber other eukaryotic algae in the oceans, especially in coastal environments characterized by frequent fluctuations in light intensity. The identities and operational mechanisms of regulatory factors governing diatom acclimation to high light stress remain largely elusive. Here, we identified the AUREO1c protein from the coastal diatom Phaeodactylum tricornutum as a crucial regulator of non-photochemical quenching (NPQ), a photoprotective mechanism that dissipates excess energy as heat. AUREO1c detects light stress using a light-oxygen-voltage (LOV) domain and directly activates the expression of target genes, including LI818 genes that encode NPQ effector proteins, via its bZIP DNA-binding domain. In comparison to a kinase-mediated pathway reported in the freshwater green alga Chlamydomonas reinhardtii, the AUREO1c pathway exhibits a faster response and enables accumulation of LI818 transcript and protein levels to comparable degrees between continuous high-light and fluctuating-light treatments. We propose that the AUREO1c-LI818 pathway contributes to the resilience of diatoms under dynamic light conditions.


Assuntos
Aclimatação , Diatomáceas , Luz , Diatomáceas/metabolismo , Diatomáceas/genética , Diatomáceas/efeitos da radiação , Chlamydomonas reinhardtii/metabolismo , Chlamydomonas reinhardtii/genética , Chlamydomonas reinhardtii/efeitos da radiação , Proteínas de Algas/metabolismo , Proteínas de Algas/genética , Regulação da Expressão Gênica/efeitos da radiação
5.
Science ; 382(6666): 92-98, 2023 10 06.
Artigo em Inglês | MEDLINE | ID: mdl-37797009

RESUMO

Marine and terrestrial photosynthesis exhibit a schism in the accessory chlorophyll (Chl) that complements the function of Chl a: Chl b for green plants versus Chl c for most eukaryotic phytoplankton. The enzymes that mediate Chl c biosynthesis have long remained elusive. In this work, we identified the CHLC dioxygenase (Phatr3_J43737) from the marine diatom Phaeodactylum tricornutum as the Chl c synthase. The chlc mutants lacked Chl c, instead accumulating its precursors, and exhibited growth defects. In vitro, recombinant CHLC protein converted these precursors into Chl c, thereby confirming its identity. Phylogenetic evidence demonstrates conserved use of CHLC across phyla but also the existence of distinct Chl c synthases in different algal groups. Our study addresses a long-outstanding question with implications for both contemporary and ancient marine photosynthesis.


Assuntos
Carbono-Oxigênio Liases , Clorofila , Diatomáceas , Fitoplâncton , Clorofila/metabolismo , Clorofila A/metabolismo , Diatomáceas/enzimologia , Diatomáceas/genética , Fotossíntese , Filogenia , Fitoplâncton/enzimologia , Proteínas Recombinantes/metabolismo , Carbono-Oxigênio Liases/classificação , Carbono-Oxigênio Liases/genética , Carbono-Oxigênio Liases/metabolismo , Mutação
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