dataesr/scientific-paragraphs-categorization huggingface dataset:
The PCR products were sent for sequencing at Macrogen Europe (https://dna. macrogen-europe. com) using the internal primer 528F (5'-CCGCGGTAATTCCAGCTC-3')  (Zhu et al. , 2005). Partial sequences were compared with those available in Genbank using the BLAST plugin in Geneious 10 (  Kearse et al. , 2012). Sequences were aligned using the ClustalW2  (Larkin et al. , 2007)  plugin in Geneious 10 and grouped into phylotypes with 100% sequence similarity. Phylotypes represented by more than one strain are listed in Supplementary Data S1. Depending on general sequence quality, partial 18S rRNA sequence alignments were built for each group, including: 49 sequences with 436 nucleotide positions for pennate diatoms, 36 sequences with 612 positions for centric diatoms, 27 sequences with 392 positions for other members of the Heterokontophyta, 52 sequences with 361 positions for Chlorophyta, 10 sequences with 638 positions for Cryptophyta, 11 sequences with 692 positions for Haptophyta, and 6 sequences with 372 positions for Alveolata (Dinophyta).
Results In the present study, partial 18S rRNA gene sequences and light microscopy were used to characterize 276 Arctic strains obtained during the Green Edge campaign ( Supplementary Data S1), 77 and 199 isolated from ice and water samples, respectively (Figure  2 ). By combining different pre-isolation and isolation techniques we were able to retrieve 276 strains assigned to 57 phylotypes characterized by 100% similarity of partial 18S rRNA sequencing. A significant level of novelty exists within these strains, as almost 60% of the representative sequences of phylotypes did not match any sequence from previously cultured strains (Table  1 ) and more than 40% did not match any existing sequence from environmental datasets. The sequence of one strain (RCC5319) had only a 95. 3% match to any existing sequence.
Diatoms -Bacillariophyceae The Cylindrotheca sp. phylotype represented by RCC5303 contains two strains from ice core samples from the pre-bloom and bloom-development phases (Supplementary Data S1). Cells are solitary with two chloroplasts, a long apical (>35 μm) and short transapical axis ( ~3 μm) ( Figure  3R ). Cylindrotheca is a genus frequently observed in the Arctic, mainly represented by the cosmopolitan species complex C. closterium  (Lovejoy et al. , 2002; Li et al. , 2007; Katsuki et al. , 2009; Poulin et al. , 2011). However, sequences from the strains obtained in this study branched apart from C. closterium (Figure  4 ), but grouped with 100% identity with an uncultured Cylindrotheca sequence from the Arctic (GenBank JF698839). The sequence of Cylindrotheca sp. RCC5216, also isolated from an IC ice core sample (Supplementary Data S1), differed from that of Cylindrotheca sp.
Interestingly, none of the Navicula spp. strains recovered in this study were related to previous polar strains or environmental sequences, despite this genus being diverse  (Katsuki et al. , 2009)  and abundant in the Arctic  (Poulin et al. , 2011; Kauko et al. , 2018). Navicula sp. strain RCC5374 was recovered from an ice core sample from the bloom-development phase. The sequence of this strain is not very closely related to those of previously reported polar Navicula, but is 99. 2% similar to strain RCC5373 and 99. 7% similar to strain KSA2015-19 from the Red Sea (Figure  4 ). Cells have a ~25 μm apical axis, slightly radiating valvar striae and rostrate ends (Figure  3J ). The Naviculales phylotype represented by RCC5564 contains 12 strains from all phases and sampling sites (Supplementary Data S1).
Its sequence is 99. 7% similar to Naviculales strain CCMP2297 from northern Baffin Bay and to uncultured sequences from the Arctic (Figure  4 ). Cells have ~3 μm apical and 5 μm pervalvar axes. They are solitary or form short chains (Figure  3AC ). The Naviculales phylotype represented by RCC5387 contains four strains from IC water and ice samples (Supplementary Data S1). Its sequence has low similarity to sequences from GenBank or to the phylotype represented by RCC5564, sharing only 96. 9% similarity with strain CCMP2297 (Naviculales) (Figure  4 ). Cells are elongated, mainly solitary, with up to 6 μm apical and 3 μm pervalvar axes (Figure  3K ). The Naviculales phylotype represented by RCC5402 has two strains, both retrieved from IC ice cores during the pre-bloom period (Supplementary Data S1).
Their sequence shares 99. 2% identity with the Bacillariophyta MBIC10102 strain from the Pacific Ocean and groups with Naviculales sequences with strong bootstrap support (91%, Figure  4 ). Cells are small ~4 μm long and 2 μm wide, sometimes solitary, but mainly forming large aggregates (Figure  3O ). The Nitzschia sp. phylotype represented by RCC5489 contains three strains from both sampling sites and substrates (Supplementary Data S1). Its sequence has no close similarity to any GenBank sequence from strains besides RCC5390 (Figure  4 ). Cells are ~11 μm wide, mainly solitary or forming small aggregates (Figure  3L ). Members of the genus Nitzschia are often reported to thrive in the Arctic  (Johnsen et al. , 2018; Kauko et al. , 2018) , with Nitzschia frigida, for example, being considered as the single most important diatom associated with sea ice  (Rózanska et al.
Nitzschia sp. RCC5458 was also retrieved from an ice sample from the pre-bloom period and its sequence is 98. 1% similar to Nitzschia sp. strain KSA2015-49 from the Red Sea (Figure  4 ). Cells are linear to lanceolate and larger than other Nitzschia strains retrieved in this study, with an apical axis up to 15 μm (Figure  3P ). Nitzschia sp. RCC5510 was isolated from AM waters (Supplementary Data S1). Its sequence is 98. 6% similar to Nitzschia sp. strain KSA2015-38 from the Red Sea (Figure  4 ). It is the only strain from this genus recovered only from AM. Its sequence branches apart from all other Nitzschia sp. (Figure  4 ). Cells are almost round in the valvar view and rather small (apical axis ~4 μm) compared to the other Nitzschia strains isolated here (Figure  3W ). The Pseudo-nitzschia arctica phylotype represented by RCC5469 contains nine strains of the recently described P.
arctica  (Percopo et al. , 2016) , all originating from IC (Supplementary Data S1). Their sequence is 100% similar to P. arctica RCC2004 (Figure  4 ), a potentially endemic species with a wide distribution in the Arctic  (Percopo et al. , 2016; Balzano et al. , 2017). Only solitary cells were observed, with lanceolate shape in valvar view, measuring ~50 μm and 3 μm for the apical and transapical axes, respectively (Figure  3S ). Sellaphora sp. strain RCC5460 was retrieved during pre-bloom from an IC ice core sample. Its sequence matches with 99% similarity that of the freshwater Sellaphora pupula strain SM-BLCAP (Figure  4 ). Cells are small, with 5 μm apical and 4 μm pervalvar axes, solitary or forming aggregates (Figure  3Q ). S. pupula is a species complex containing many pseudo-and semi-cryptic representatives capable of thriving in a wide range of environmental conditions  (Poulíčková et al.
Diatoms -Coscinodiscophyceae The Actinocyclus sp. phylotype represented by RCC5608 comprises two strains isolated from AM waters (Supplementary Data S1). Its sequence shares 100% similarity with a clone from the Arctic (EU371328), and 99. 8% with the Actinocyclus sp. MPA-2013 isolate from the Pacific Ocean (Figure  5 ). Cells have a pervalvar axis (13-17 μm) longer than the valvar diameter ( ~5 μm) and discoid chloroplasts (Figure  3AG ). Although sometimes spotted in low abundance  (Katsuki et al. , 2009; Crawford et al. , 2018) , this genus may dominate phytoplankton biomass in Arctic spring blooms  (Lovejoy et al. , 2002). Coscinodiscus sp. strain RCC5319 was isolated from an IC under-ice sample at the peak of the bloom (Supplementary Data S1). The sequence is only 95% similar to that of C.
Their sequence shares 100% similarity with the Arctic strain RCC1988 (Figure  5 ). Cells are lightly silicified with ~6 μm pervalvar axis and horns up to two times the cell length. They are either solitary or form big aggregates (Figure  3AD ). A. septentrionalis is often reported in abundance in Arctic waters and ice  (Assmy et al. , 2013; Balzano et al. , 2017) , outcompeting pennate diatoms in high-luminosity/low nutrient conditions  (Campbell et al. , 2017). The Attheya longicornis phylotype represented by RCC5555 contains 14 strains, 11 of which were retrieved from AM water samples (Supplementary Data S1). Sequences are 100% identical to the Arctic A. longicornis strains RCC4284 and CCMP214 (Figure  5 ). Cells are often solitary or in short chains, with horns up to three times the length of the pervalvar axis (Figure  3AB ).
Their sequences were 100% similar to those of the Arctic strains RCC4290 and RCC1992 (Figure  5 ). Cells are rectangular ( ~6 μm), forming small, tight chains with narrow apertures and long inner setae, up to 25 μm (Figure  3C ). C. gelidus is a recently described species, previously considered as a Chaetoceros socialis ecotype, and is characteristic of northern temperate and polar waters  (Chamnansinp et al. , 2013). It is reported to form blooms  (Booth et al. , 2002)  and can represent an important fraction of diatom abundance and biomass in Baffin Bay  (Crawford et al. , 2018). Chaetoceros decipiens strain RCC5606 was isolated from 30-m depth in AM water (Supplementary Data S1). Its sequence is 99. 8% similar to Arctic strain C. decipiens RCC1997 (Figure  5 ). Cells ( ~10-30 μm apical axis) have very long inner setae (>100 μm) and form short, semicircular colonies (Figure  3AF ), which contrasts with previous morphological descriptions of C.
decipiens  (Hasle and Syvertsen, 1997; Balzano et al. , 2017) , indicating that it might correspond to a new phylotype. This cosmopolitan species has frequently been reported in the Arctic, both in ice and open waters  (Lovejoy et al. , 2002; Joo et al. , 2012; Johnsen et al. , 2018). Eucampia groenlandica RCC5531 strain was retrieved from 30 m depth during the Amundsen cruise. Its sequence shares 100% similarity with E. groenlandica Arctic strain RCC2038 (Figure  5 ). Cells are lightly silicified with varying sizes, forming straight or moderately curved colonies (Figure  3Y ). E. groenlandica was first reported in Baffin Bay  (Cleve, 1896)  although its distribution is not constrained to the Arctic  (Lee and Lee, 2012). The Shionodiscus bioculatus phylotype represented by RCC5532 contains two strains isolated from the AM (Supplementary Data S1).
Cells are colorless and solitary, round or slightly elongated with 4 μm diameter and 5 μm flagella (Figure  7N ). Heterotrophic flagellates from the genus Spumella have been previously reported in the Arctic  (Lovejoy et al. , 2006)  and are mostly cold-adapted and associated with lower salinities  (Grossmann et al. , 2015). The Spumella sp. phylotype represented by RCC5412 contains two isolates from IC waters. Their sequence is 100% similar to those of Spumella sp. isolate CCAP 955/1 from a soil sample collected in China and Spumella elongata isolate JBC/S24 from the UK (Figure  6A ). Interestingly, these sequences are part of a soil sub-cluster within Chrysophyceae clade C with few aquatic representatives  (Boenigk et al. , 2005). These strains were lost and no images are available. Pedinellales strain RCC5264 was retrieved from an IC ice sample at the peak of the bloom (Supplementary Data S1), and its sequence matched with 100% similarity that of the undescribed Pedinellales Arctic strain RCC2301 and also with CCMP2098 isolated from Baffin Bay (GenBank EU247836).
Chlorophyta The Chlamydomonas sp. phylotype represented by RCC5305 contains 6 strains isolated from IC water and ice samples from the peak of the bloom and is the only representative of the Chlorophyceae in our set of culture isolates (Supplementary Data S1). Its sequence is 100% identical to sequences from the Chlamydomonas pulsatilla polar strain CCCryo 038-99, but also strains from Antarctic ice and Arctic fresh water (Figure  8 ), all belonging to the Polytoma clade  (Pocock et al. , 2004). Cells are round or elongated, ~7 μm in diameter or 10 μm long, respectively (Figure  7H ). Chlamydomonas is a common genus found in the Arctic during the spring and summer months  (Lovejoy et al. , 2002; Balzano et al. , 2012a) , that can occur in association with sea-ice  (Majaneva et al. , 2017). Bathycoccus prasinos RCC5417 strain was recovered from an IC ice core sample during bloom development (Supplementary Data S1).
RCC1987. These strains were lost and no images are available. Pyramimonas australis RCC5269 strain from IC water has a sequence matching with 100% similarity that of P. australis (GenBank AJ404886) from the subgenus Trichocystis, an Antarctic species described based on light/electron microscopy, nuclear-encoded small-subunit ribosomal DNA and chloroplast-encoded rbcL gene sequences, but with no representative sequence from cultures until now  (Moro et al. , 2002). Cells are pear-like to almost oval, ~10 μm long and 6 μm wide with four flagella (Figure  7E ). Pyramimonas sp. RCC5483 strain was recovered from IC surface waters during the pre-bloom phase and its sequence shares 100% similarity with that of the Arctic strain RCC669 (Figure  8 ). This strain was lost and no images are available.
Cryptophyta The Baffinella frigidus phylotype represented by RCC5246 contains 13 strains collected from IC water and ice samples (Supplementary Data S1). Their representative sequence matches with 100% similarity those of the B. frigidus sp. strain CCMP2045 (Figure  6B ). This genus was originally isolated from Baffin Bay and is the first Cryptophyta representative described from this region  (Daugbjerg et al. , 2018). Cells are ~10 μm long and 5 μm wide with a prominent pyrenoid (Figure  7A ). The Rhodomonas sp. phylotype represented by RCC5610 groups 3 strains, 2 of them isolated from IC and one from AM water samples (Supplementary Data S1). Its representative sequence has low similarity to that of RCC5246 (96. 8%) and is 100% similar to other Arctic strains such as RCC2020 and Rhodomonas marina SCCAP K-0435 from Denmark (Figure  6B ), a species associated with sea ice  (Niemi et al.
Haptophyta Pseudohaptolina sorokinii strain (RCC5270) was retrieved from IC water during the peak of the bloom. Its sequence shares 100% similarity with that of the recently described P. sorokinii  (Orlova et al. , 2016)  strain PsAB2015 collected from coastal, under-ice water and 99. 7% with the strain P. arctica CCMP 1204 (Figure  6C ). Cells are round to oblong, ~17 μm in length and 12 μm in width. The two flagella have almost the same length as the cell, with a shorter haptonema (Figure  7F ). The Isochrysis sp. phylotype represented by RCC5486 contains three strains, all retrieved from IC ice core samples. Their sequence shared low similarity to any other cultured strain in the GenBank database, matching with 99. 2% identity the Isochrysis nuda strain RCC2477 and 99. 1% Isochrysis galbana strain 24-25B5 (Figure  6C ).
Ice Camp A total of 187 strains were isolated from IC samples, 110 from the water and 77 from the ice (Supplementary Data S1). Diatoms dominated isolates from all phases of the bloom (pre-bloom, bloom-development and bloom-peak), although the diversity and number of strains varied ( Figure  9 ). During the pre-bloom phase, 28 strains were recovered from the ice and 10 from the water, belonging to six classes (Figure  9 ). This phase was dominated by Bacillariophyceae, mainly Nitzschia and F. cylindrus ( Figure  9 , Supplementary Data S1). Eight out of the eleven Mediophyceae strains belonged to the genus Thalassiosira. Strains from Pyramimonadales, Prymnesiophyceae, Pelagophyceae and Mamiellophyceae were also retrieved during pre-bloom. The bloom-development phase yielded 50 strains from seven classes.
New taxa not isolated during the first phase appeared in this second phase, including one strain of Pedinellales (Dictyochophyceae) from an ice sample, and 7 strains of Cryptophyceae assigned to Rhodomonas and Baffinella, all from water samples (Figure  9 , Supplementary Data S1). More strains were retrieved during the bloom-peak phase than the other two phases combined (99), and 11 classes were isolated. In contrast to the previous two phases, strains retrieved from water were more diverse than from the ice (Figure  9 ). Chlorophyceae were represented by Chlamydomonas sp. , from both water and ice samples. One strain of the Prymnesiophyceae P. sorokinii and the Chrysophyceae strains D. faculiferum and Spumella spp. were only retrieved during this phase ( Supplementary Data S1). With respect to diatoms, this phase was marked by an increase in Mediophyceae, particularly from the genera Chaetoceros and Attheya ( Supplementary Data S1).
Amundsen cruise A total of 89 strains were isolated from AM water samples, of which 81 were diatoms. Although some stations were dominated by Bacillariophyceae, such as station G102, the majority of the strains belonged to the Mediophyceae, particularly Attheya spp. and C. neogracilis (Supplementary Data S1). Only two strains of the Coscinodiscophyceae genus Actinocyclus sp. were recovered, both from surface waters at the same station (G713). Few non-diatom strains were isolated. The only station with Cryptophyceae representatives was AM1, from which one Rhodomonas strain was isolated (Figure  S2 ). Four Dinophyceae strains (Biecheleria spp. ) were retrieved from station G204. One strain of Spumella sp. was recovered from G110 and two Pyramimonas sp. strains from G512 and G707 ( Supplementary Data S1).
Isolation method Serial dilution yielded the most phylotypes (18), followed by FCM cell sorting (  14 ) and single cell pipetting (7). Eighteen phylotypes had representatives isolated by more than one technique (Figure  S3 ). Among diatoms, Bacillariophyceae and Mediophyceae were retrieved by the three isolation methods, but Coscinodiscophyceae were isolated only by single cell pipetting (Figure  S4A  to C). Specifically, Arcocellulus sp. and E. groenlandica were retrieved only by flow cytometry sorting, while B. bathyomphala, Coscinodiscus sp. and Actinocyclus sp. strains came only from single cell pipetting. The strains isolated only by serial dilution included Sellaphora sp. , Skeletonema sp. and one Naviculales phylotype (Supplementary Data S1). For non-diatoms, FCM cell sorting was the technique which retrieved the highest diversity at the class level (Figure  S4F ).
Funding information Financial support for this work was provided by the  Green Edge project  ( ANR-14-CE01-0017 ,  Fondation Total) , the  ANR PhytoPol  ( ANR-15-CE02-0007 ) and  TaxMArc (Research Council of Norway ,  268286/E40 ). M. T. was supported by a PhD fellowship from the  Université Pierre et Marie Curie  and the  Région Bretagne (ARED GreenPhy ). ALS was supported by  FONDECYT grant PiSCOSouth  ( N1171802 ). CGR was supported by  CONICYT  project  3190827.
, 2017a). Analysis of the two genotypes identified 2,288 unique N termini corresponding to 1,043 nonredundant proteoforms and 824 distinct protein entities (PRIDE repository, identifier PXD017430). Among all identified proteoforms, 480 unique N termini (392 in the wild type and 309 in naa50-2) were quantified. Of the quantified N termini, 192 underwent the removal of iMet (40%) and 43 (9%) retained their iMet, while the remaining 245 (51%) are neo-N termini formed after intracellular maturation Table  1. The N-terminal acetylation yield of NatA substrates is unaffected in naa50-2 mutants Data are from proteins quantified in at least two biological replicate of the wild type and amiNaa10. When no quantitative acetylation data were obtained in the naa50-2 data set, the N-terminal status was specified instead.
B, The differentially regulated proteins (first pie chart, downregulated in naa50-2 compared with the wild type; second pie chart, up-regulated in naa50-2 compared with the wild type) are localized in a variety of cellular compartments, according to the SUB-Acon localization of the SUBA4 Arabidopsis subcellular localization database  (Hooper et al. , 2017). For comparison, the distribution of localizations was calculated for all proteins detected in the MS approach (third pie chart, designated background). The full list of quantified protein groups is available in Supplemental Table  S2. N. A. , Not available. groups, which corresponds to 16% of the quantified protein groups (4,508 protein groups; Supplemental Table  S2 ). The 20 most affected proteins are listed in Table  2. The abundance of 541 protein groups increased significantly in naa50-2, while 191 protein groups were found to be downregulated (Fig.
SDS-PAGE and Immunological Detection Protein extracts were analyzed via SDS-PAGE  (Laemmli, 1970)  and blotted onto polyvinylidene difluoride membranes using Mini-Protean II cells (Bio-Rad). The primary NAA50 antibody and the secondary horseradish peroxidaselinked anti-rabbit antibody (no. AS10 852, Agrisera) were diluted 1:5,000 and 1:25,000 in 13 Tris-buffered saline plus Tween 20 (50 mM Tris, pH 7. 6, 150 mM NaCl, and 0. 05% [v/v] Tween 20) supplemented with 0. 5% (w/v) BSA. Membranes were developed using the SuperSignal West Dura Extended Duration Substrate (Thermo Scientific) according to the manufacturer's instructions. The resulting signals were recorded using the ImageQuant LAS 4000 (GE Healthcare) and subsequently quantified with the ImageQuant TL software (GE Healthcare).
GAP and Data Analysis GAP was performed as previously described by  Dinh et al. (2015). For this purpose, 1 mg of E. coli lysates expressing AtNAA50-SUMO or SUMO-GFP as a negative control was subjected to chemical acetylation of free N termini with N-acetoxy-[2H3]-succinimide required for SILProNAQ quantification  (Bienvenut et al. , 2017a). The samples were digested with trypsin, and the N-terminal peptides were enriched by strong cation-exchange liquid chromatography before liquid chromatography-tandem mass spectrometry (LC-MS/ MS) analysis. Raw data were extracted and exported with Proteome Discoverer (Thermo Scientific, version 1. 4). The MASCOT 2. 4 software was used for the identification of proteins and their cotranslational and posttranslational modifications. The E. coli K12 strain proteome extracted from UniProtKB (version 112) served as a reference proteome.
Acts as a Nat with Broad Substrate Specificity BLAST searches with NAA50 from human or yeast identify AT5G11340 as a putative ortholog of NAA50 1 This work was supported by the Deutsche Forschungsgemeinschaft via the Collaborative Research Centre (grant no. SFP1036, TP13 to R. H. and M. W. , TP 22 to I. Si. , FI 1655/3-1 and INST 211/ 744-1 to I. F. , and WI 3560/4-1 to M. W. ) and by the Leibniz Programme (to I. Si). C. G. was supported by the Agence Nationale de la Recherche (grant no. ANR-10-LABX-0040-SPS) and by the facilities and expertise of the Institute of Integrative Biology of the Cell Service for the Identification and Characterization of Proteins by Mass Spectrometry proteomic platform, supported by Infrastructures in Biology Health and Agronomy, Ile de France Region, Plan Cancer, French National Centre for Scientific Research, and Paris-Sud University.
Acknowledgements We thank the  Deutsche Forschungsgemeinschaft (DFG ,  Schu/12-1 ) and the  French National Agency for Research (ANR)  for financial support. We thank the Peruvian authorities and  Dr Gerardo Lamas  ( Museo de Historia Natural, Universidad Mayor de San Marcos ) for research permits ( 236-2012-AG-DGFFS-DGEFFS ). We also thank  Armando Silva-Vásquez  and  Stéphanie Galusser  for their precious help in the field. Melanie McClure allowed usage of her Ihomia-photo in the graphical abstract. Céline Houssin  allowed usage of her photos of Ithomia salapia aquinia and Ithomia salapia derasa in the supporting information.