scholarly journals Characterization of the Chlamydomonas reinhardtii phycosphere reveals conserved features of the plant microbiota

2021 ◽  
Author(s):  
Paloma Durán ◽  
José Flores-Uribe ◽  
Kathrin Wippel ◽  
Pengfan Zhang ◽  
Rui Guan ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Chlamydomonas Reinhardtii ◽  
Heterotrophic Bacteria ◽  
Flowering Plants ◽  
Land Plants ◽  
Photosynthetic Organisms ◽  
Ecological Principles ◽  
Plant Microbiota ◽  
Root Microbiota

AbstractMicroscopic algae release organic compounds to the region immediately surrounding their cells, known as the phycosphere, constituting a niche for colonization by heterotrophic bacteria. These bacteria take up algal photoassimilates and provide beneficial functions to their host, in a process that resembles the establishment of microbial communities associated with the roots and rhizospheres of land plants. Here, we characterize the microbiota of the model alga Chlamydomonas reinhardtii and reveal extensive taxonomic and functional overlap with the root microbiota of land plants. Reconstitution experiments using synthetic communities derived from C. reinhardtii and Arabidopsis thaliana show that phycosphere and root bacteria assemble into taxonomically equivalent communities on either host. We show that provision of diffusible metabolites is not sufficient for phycosphere community establishment, which additionally requires physical proximity to the host. Our data suggests that the microbiota of photosynthetic organisms, including green algae and flowering plants, assembles according to core ecological principles.

scholarly journals Deep evolutionary origin of gamete-directed zygote activation by KNOX/BELL transcription factors in green plants

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Tetsuya Hisanaga ◽  
Shota Fujimoto ◽  
Yihui Cui ◽  
Katsutoshi Sato ◽  
Ryosuke Sano ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Transcription Factors ◽  
Chlamydomonas Reinhardtii ◽  
Plant Species ◽  
Land Plant ◽  
Land Plants ◽  
Marchantia Polymorpha ◽  
Mating Types ◽  
Meristem Maintenance

KNOX and BELL transcription factors regulate distinct steps of diploid development in plants. In the green alga Chlamydomonas reinhardtii, KNOX and BELL proteins are inherited by gametes of the opposite mating types and heterodimerize in zygotes to activate diploid development. By contrast, in land plants such as Physcomitrium patens and Arabidopsis thaliana, KNOX and BELL proteins function in meristem maintenance and organogenesis during the later stages of diploid development. However, whether the contrasting functions of KNOX and BELL were acquired independently in algae and land plants is currently unknown. Here, we show that in the basal land plant species Marchantia polymorpha, gamete-expressed KNOX and BELL are required to initiate zygotic development by promoting nuclear fusion in a manner strikingly similar to that in C. reinhardtii. Our results indicate that zygote activation is the ancestral role of KNOX/BELL transcription factors, which shifted toward meristem maintenance as land plants evolved.

scholarly journals Current knowledge and recent advances in understanding metabolism of the model cyanobacterium Synechocystis sp. PCC 6803

2020 ◽  
Vol 40 (4) ◽  
Author(s):  
Lauren A. Mills ◽  
Alistair J. McCormick ◽  
David J. Lea-Smith
Keyword(s):  
Amino Acids ◽  
Heterotrophic Bacteria ◽  
Membrane Lipids ◽  
Current Knowledge ◽  
Oxygenic Photosynthesis ◽  
Photosynthetic Organisms ◽  
Physiological Processes ◽  
Synechocystis Sp ◽  
Pcc 6803

Abstract Cyanobacteria are key organisms in the global ecosystem, useful models for studying metabolic and physiological processes conserved in photosynthetic organisms, and potential renewable platforms for production of chemicals. Characterizing cyanobacterial metabolism and physiology is key to understanding their role in the environment and unlocking their potential for biotechnology applications. Many aspects of cyanobacterial biology differ from heterotrophic bacteria. For example, most cyanobacteria incorporate a series of internal thylakoid membranes where both oxygenic photosynthesis and respiration occur, while CO2 fixation takes place in specialized compartments termed carboxysomes. In this review, we provide a comprehensive summary of our knowledge on cyanobacterial physiology and the pathways in Synechocystis sp. PCC 6803 (Synechocystis) involved in biosynthesis of sugar-based metabolites, amino acids, nucleotides, lipids, cofactors, vitamins, isoprenoids, pigments and cell wall components, in addition to the proteins involved in metabolite transport. While some pathways are conserved between model cyanobacteria, such as Synechocystis, and model heterotrophic bacteria like Escherichia coli, many enzymes and/or pathways involved in the biosynthesis of key metabolites in cyanobacteria have not been completely characterized. These include pathways required for biosynthesis of chorismate and membrane lipids, nucleotides, several amino acids, vitamins and cofactors, and isoprenoids such as plastoquinone, carotenoids, and tocopherols. Moreover, our understanding of photorespiration, lipopolysaccharide assembly and transport, and degradation of lipids, sucrose, most vitamins and amino acids, and haem, is incomplete. We discuss tools that may aid our understanding of cyanobacterial metabolism, notably CyanoSource, a barcoded library of targeted Synechocystis mutants, which will significantly accelerate characterization of individual proteins.

scholarly journals Brassinosteroids repress the seed maturation program during the seed-to-seedling transition

2021 ◽  
Author(s):  
Jiuxiao Ruan ◽  
Huhui Chen ◽  
Tao Zhu ◽  
Yaoguang Yu ◽  
Yawen Lei ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Transcription Factor ◽  
Abscisic Acid ◽  
Plant Hormone ◽  
Flowering Plants ◽  
Seed Maturation ◽  
Domain Protein ◽  
Abscisic Acid Insensitive3 ◽  
Underlying Mechanisms ◽  
Embryonic Structure

Abstract In flowering plants, repression of the seed maturation program is essential for the transition from the seed to the vegetative phase, but the underlying mechanisms remain poorly understood. The B3-domain protein VIVIPAROUS1/ABSCISIC ACID-INSENSITIVE3-LIKE 1 (VAL1) is involved in repressing the seed maturation program. Here we uncovered a molecular network triggered by the plant hormone brassinosteroid (BR) that inhibits the seed maturation program during the seed-to-seedling transition in Arabidopsis (Arabidopsis thaliana). val1-2 mutant seedlings treated with a BR biosynthesis inhibitor form embryonic structures, whereas BR signaling gain-of-function mutations rescue the embryonic structure trait. Furthermore, the BR-activated transcription factors BRI1-EMS-SUPPRESSOR 1 and BRASSINAZOLE-RESISTANT 1 bind directly to the promoter of AGAMOUS-LIKE15 (AGL15), which encodes a transcription factor involved in activating the seed maturation program, and suppress its expression. Genetic analysis indicated that BR signaling is epistatic to AGL15 and represses the seed maturation program by downregulating AGL15. Finally, we showed that the BR-mediated pathway functions synergistically with the VAL1/2-mediated pathway to ensure the full repression of the seed maturation program. Together, our work uncovered a mechanism underlying the suppression of the seed maturation program, shedding light on how BR promotes seedling growth.

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