Plant Protein O-Arabinosylation

Petersen, Bent; MacAlister, Cora A.; Ulvskov, Peter

doi:10.3389/fpls.2021.645219

Cited by 28 publications

(22 citation statements)

References 122 publications

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“…Ambtr41.53 Given that the HPATs are glycosyltransferases, we expect that the hpat1/3 phenotype reflects the impact of the loss of hydroxyproline O-arabinosylation from the proteins that they modify. The largest known group of HPAT-modified proteins are the EXT cell wall structural proteins (Petersen et al, 2021). The EXTs form a cross-linked network and are hypothesized to serve as a scaffold for the assembly of pectin during cell wall formation (Cannon et al, 2008).…”

Section: Discussionmentioning

confidence: 99%

SEC1A is a major Arabidopsis Sec1/Munc18 gene in vesicle trafficking during pollen tube tip growth

et al. 2022

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SUMMARY Pollen tubes (PTs) grow by the targeted secretion of new cell wall material to their expanding tip region. Sec1/Munc18 (SM) proteins promote membrane fusion through regulation of the SNARE complex. We have previously shown that disruption of protein glycosylation in the Arabidopsis thaliana hpat1 hpat3 double mutant leads to PT growth defects that can be suppressed by reducing secretion. Here, we identified five point mutant alleles of the SM protein SEC1A as hpat1/3 suppressors. The suppressors increased seed set, reduced PT growth defects and reduced the rate of glycoprotein secretion. In the absence of the hpat mutations, sec1a reduced pollen germination and PT elongation producing shorter and wider PTs. Consistent with a defect in membrane fusion, sec1a PTs accumulated secretory vesicles. Though sec1a had significantly reduced male transmission, homozygous sec1a plants maintained full seed set, demonstrating that SEC1A was ultimately dispensable for pollen fertility. However, when combined with a mutation in another SEC1‐like SM gene, keule, pollen fertility was totally abolished. Mutation in sec1b, the final member of the Arabidopsis SEC1 clade, did not enhance the sec1a phenotype. Thus, SEC1A is the major SM protein promoting pollen germination and tube elongation, but in its absence KEULE can partially supply this activity. When we examined the expression of the SM protein family in other species for which pollen expression data were available, we found that at least one Sec1‐like protein was highly expressed in pollen samples, suggesting a conserved role in pollen fertility in other species.

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Section: Discussionmentioning

confidence: 99%

SEC1A is a major Arabidopsis Sec1/Munc18 gene in vesicle trafficking during pollen tube tip growth

et al. 2022

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“…This diversity originates from the combination of different monosaccharides and various linkages, generated by a huge variety of glycosyltransferases from which a considerable amount has not been thoroughly characterized yet (Showalter and Basu, 2016;Amos and Mohnen, 2019). Some enzymes responsible for the attachment of arabinoses to β1,4-linked galactoses on O-glycosylated arabinogalactan proteins as well as in cell-wall associated structures like rhamnogalaturan I have been described, but many still remain unknown (Léonard et al, 2010;Laursen et al, 2018;Ropartz and Ralet, 2020;Petersen et al, 2021). The identification of the enzyme or enzymes responsible for the arabinosylation of galactosylated N-glycans is therefore not a straightforward task.…”

Section: Discussionmentioning

confidence: 99%

Unexpected Arabinosylation after Humanization of Plant Protein N-Glycosylation

Bohlender

Parsons

Hoernstein

et al. 2022

Front. Bioeng. Biotechnol.

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As biopharmaceuticals, recombinant proteins have become indispensable tools in medicine. An increasing demand, not only in quantity but also in diversity, drives the constant development and improvement of production platforms. The N-glycosylation pattern on biopharmaceuticals plays an important role in activity, serum half-life and immunogenicity. Therefore, production platforms with tailored protein N-glycosylation are of great interest. Plant-based systems have already demonstrated their potential to produce pharmaceutically relevant recombinant proteins, although their N-glycan patterns differ from those in humans. Plants have shown great plasticity towards the manipulation of their glycosylation machinery, and some have already been glyco-engineered in order to avoid the attachment of plant-typical, putatively immunogenic sugar residues. This resulted in complex-type N-glycans with a core structure identical to the human one. Compared to humans, plants lack the ability to elongate these N-glycans with β1,4-linked galactoses and terminal sialic acids. However, these modifications, which require the activity of several mammalian enzymes, have already been achieved for Nicotiana benthamiana and the moss Physcomitrella. Here, we present the first step towards sialylation of recombinant glycoproteins in Physcomitrella, human β1,4-linked terminal N-glycan galactosylation, which was achieved by the introduction of a chimeric β1,4-galactosyltransferase (FTGT). This chimeric enzyme consists of the moss α1,4-fucosyltransferase transmembrane domain, fused to the catalytic domain of the human β1,4-galactosyltransferase. Stable FTGT expression led to the desired β1,4-galactosylation. However, additional pentoses of unknown identity were also observed. The nature of these pentoses was subsequently determined by Western blot and enzymatic digestion followed by mass spectrometric analysis and resulted in their identification as α-linked arabinoses. Since a pentosylation of β1,4-galactosylated N-glycans was reported earlier, e.g., on recombinant human erythropoietin produced in glyco-engineered Nicotiana tabacum, this phenomenon is of a more general importance for plant-based production platforms. Arabinoses, which are absent in humans, may prevent the full humanization of plant-derived products. Therefore, the identification of these pentoses as arabinoses is important as it creates the basis for their abolishment to ensure the production of safe biopharmaceuticals in plant-based systems.

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“…Other possible microspore cell wall components include cell wall-associated proteins, for example, the extensins or arabinogalactan glycoproteins (AGPs). The extensins are moderately glycosylated, highly repetitive proteins, which can be covalently cross-linked in the wall by secreted peroxidases, possibly forming a scaffold for pectin assembly (Schnabelrauch et al, 1996 ; Cannon et al, 2008 ; Petersen et al, 2021 ). In Arabidopsis peroxidase9 ( prx9 ) and prx40 double mutants, microspores and tapetal cells have a swollen phenotype, suggesting compromised cell wall integrity due to a reduction in extensin cross-linking during pollen development (Jacobowitz et al, 2019 ).…”

Section: Discussionmentioning

confidence: 99%

Sequential Deposition and Remodeling of Cell Wall Polymers During Tomato Pollen Development

Jaffri

MacAlister

2021

Front. Plant Sci.

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The cell wall of a mature pollen grain is a highly specialized, multilayered structure. The outer, sporopollenin-based exine provides protection and support to the pollen grain, while the inner intine, composed primarily of cellulose, is important for pollen germination. The formation of the mature pollen grain wall takes place within the anther with contributions of cell wall material from both the developing pollen grain as well as the surrounding cells of the tapetum. The process of wall development is complex; multiple cell wall polymers are deposited, some transiently, in a controlled sequence of events. Tomato (Solanum lycopersicum) is an important agricultural crop, which requires successful fertilization for fruit production as do many other members of the Solanaceae family. Despite the importance of pollen development for tomato, little is known about the detailed pollen gain wall developmental process. Here, we describe the structure of the tomato pollen wall and establish a developmental timeline of its formation. Mature tomato pollen is released from the anther in a dehydrated state and is tricolpate, with three long apertures without overlaying exine from which the pollen tube may emerge. Using histology and immunostaining, we determined the order in which key cell wall polymers were deposited with respect to overall pollen and anther development. Pollen development began in young flower buds when the premeiotic microspore mother cells (MMCs) began losing their cellulose primary cell wall. Following meiosis, the still conjoined microspores progressed to the tetrad stage characterized by a temporary, thick callose wall. Breakdown of the callose wall released the individual early microspores. Exine deposition began with the secretion of the sporopollenin foot layer. At the late microspore stage, exine deposition was completed and the tapetum degenerated. The pollen underwent mitosis to produce bicellular pollen; at which point, intine formation began, continuing through to pollen maturation. The entire cell wall development process was also punctuated by dynamic changes in pectin composition, particularly changes in methyl-esterified and de-methyl-esterified homogalacturonan.

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Plant Protein O-Arabinosylation

Cited by 28 publications

References 122 publications

SEC1A is a major Arabidopsis Sec1/Munc18 gene in vesicle trafficking during pollen tube tip growth

SEC1A is a major Arabidopsis Sec1/Munc18 gene in vesicle trafficking during pollen tube tip growth

Unexpected Arabinosylation after Humanization of Plant Protein N-Glycosylation

Sequential Deposition and Remodeling of Cell Wall Polymers During Tomato Pollen Development

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