PECTIN METHYLESTERASE INHIBITOR6 Promotes <i>Arabidopsis</i> Mucilage Release by Limiting Methylesterification of Homogalacturonan in Seed Coat Epidermal Cells

Saéz-Aguayo, Susana; Ralet, Marie-Christine; Berger, Adeline; Botran, Lucy; Ropartz, David; Marion‐Poll, Annie; North, Helen

doi:10.1105/tpc.112.106575

Cited by 126 publications

(228 citation statements)

References 67 publications

(132 reference statements)

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“…If SOS5 does not mediate its effects on cell wall structure through cellulose, it must function through other mechanisms. The composition and modification of mucilage pectin (RG I and HG) have also been shown to influence the structure and adherence of mucilage (Dean et al, 2007;Macquet et al, 2007b;Rautengarten et al, 2008;Arsovski et al, 2009;Saez-Aguayo et al, 2013;Voiniciuc et al, 2013). Although both SOS5 and CESA5 are required for the adherence of mucilage pectin, several lines of evidence suggest that SOS5 has a much stronger effect than CESA5.…”

Section: Sos5 Has a Greater Impact On Mucilage Pectin Whereas Cesa5 mentioning

confidence: 99%

“…For example, both SUBTILISIN-LIKE SER PROTEASE1.7 and PECTIN METHYLESTERASE INHIBITOR6 are required for proper methyl esterification of mucilage (Rautengarten et al, 2008;Saez-Aguayo et al, 2013). Mutations in another gene, FLYING SAUCER1 (FLY1; a transmembrane E3 ubiquitin ligase), reduce the degree of pectin methylesterification in mucilage and cause increased mucilage adherence and defective mucilage extrusion (Voiniciuc et al, 2013).…”

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confidence: 99%

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SALT-OVERLY SENSITIVE5 Mediates Arabidopsis Seed Coat Mucilage Adherence and Organization through Pectins

Griffiths¹,

Tsai²,

Xue

et al. 2014

Plant Physiology

135

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Interactions between cell wall polymers are critical for establishing cell wall integrity and cell-cell adhesion. Here, we exploit the Arabidopsis (Arabidopsis thaliana) seed coat mucilage system to examine cell wall polymer interactions. On hydration, seeds release an adherent mucilage layer strongly attached to the seed in addition to a nonadherent layer that can be removed by gentle agitation. Rhamnogalacturonan I (RG I) is the primary component of adherent mucilage, with homogalacturonan, cellulose, and xyloglucan constituting minor components. Adherent mucilage contains rays composed of cellulose and pectin that extend above the center of each epidermal cell. CELLULOSE SYNTHASE5 (CESA5) and the arabinogalactan protein SALT-OVERLY SENSITIVE5 (SOS5) are required for mucilage adherence through unknown mechanisms. SOS5 has been suggested to mediate adherence by influencing cellulose biosynthesis. We, therefore, investigated the relationship between SOS5 and CESA5. cesa5-1 seeds show reduced cellulose, RG I, and ray size in adherent mucilage. In contrast, sos5-2 seeds have wild-type levels of cellulose but completely lack adherent RG I and rays. Thus, relative to each other, cesa5-1 has a greater effect on cellulose, whereas sos5-2 mainly affects pectin. The double mutant cesa5-1 sos5-2 has a much more severe loss of mucilage adherence, suggesting that SOS5 and CESA5 function independently. Doublemutant analyses with mutations in MUCILAGE MODIFIED2 and FLYING SAUCER1 that reduce mucilage release through pectin modification suggest that only SOS5 influences pectin-mediated adherence. Together, these findings suggest that SOS5 mediates adherence through pectins and does so independently of but in concert with cellulose synthesized by CESA5.

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Section: Sos5 Has a Greater Impact On Mucilage Pectin Whereas Cesa5 mentioning

confidence: 99%

mentioning

confidence: 99%

SALT-OVERLY SENSITIVE5 Mediates Arabidopsis Seed Coat Mucilage Adherence and Organization through Pectins

Griffiths¹,

Tsai²,

Xue

et al. 2014

Plant Physiology

135

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“…As with the nonadherent layer, adherent mucilage is also mainly composed of unbranched RG-I, but with small numbers of arabinan and galactan ramifications (Penfield et al, 2001;Willats et al, 2001;Dean et al, 2007;Macquet et al, 2007aMacquet et al, , 2007bArsovski et al, 2009;Haughn and Western, 2012). There are also minor amounts of pectic HG in the adherent mucilage, with high methylesterified HG in the external domain compared with the internal domain of the adherent layer (Willats et al, 2001;Macquet et al, 2007a;Rautengarten et al, 2008;Sullivan et al, 2011;Saez-Aguayo et al, 2013). In addition, the adherent mucilage contains cellulose (Blake et al, 2006;Macquet et al, 2007a), which is entangled with RG-I and is thought to anchor the pectinrich mucilage onto seeds (Macquet et al, 2007a; HarpazSaad et al, 2011 HarpazSaad et al, , 2012Mendu et al, 2011;Sullivan et al, 2011).…”

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confidence: 99%

“…PECTIN METHYLESTERASE INHIBITOR6 (PMEI6) inhibits PME activities (SaezAguayo et al, 2013). The subtilisin-like Ser protease (SBT1.7) can activate other PME inhibitors, but not PMEI6 (Rautengarten et al, 2008;Saez-Aguayo et al, 2013). Disruption of either PMEI6 or SBT1.7 results in the delay of mucilage release.…”

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confidence: 99%

CELLULOSE SYNTHASE-LIKE A2, a Glucomannan Synthase, Is Involved in Maintaining Adherent Mucilage Structure in Arabidopsis Seed

Shi

et al. 2014

Plant Physiol.

135

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Mannans are hemicellulosic polysaccharides that are considered to have both structural and storage functions in the plant cell wall. However, it is not yet known how mannans function in Arabidopsis (Arabidopsis thaliana) seed mucilage. In this study, CELLULOSE SYNTHASE-LIKE A2 (CSLA2; At5g22740) expression was observed in several seed tissues, including the epidermal cells of developing seed coats. Disruption of CSLA2 resulted in thinner adherent mucilage halos, although the total amount of the adherent mucilage did not change compared with the wild type. This suggested that the adherent mucilage in the mutant was more compact compared with that of the wild type. In accordance with the role of CSLA2 in glucomannan synthesis, csla2-1 mucilage contained 30% less mannosyl and glucosyl content than did the wild type. No appreciable changes in the composition, structure, or macromolecular properties were observed for nonmannan polysaccharides in mutant mucilage. Biochemical analysis revealed that cellulose crystallinity was substantially reduced in csla2-1 mucilage; this was supported by the removal of most mucilage cellulose through treatment of csla2-1 seeds with endo-b-glucanase. Mutation in CSLA2 also resulted in altered spatial distribution of cellulose and an absence of birefringent cellulose microfibrils within the adherent mucilage. As with the observed changes in crystalline cellulose, the spatial distribution of pectin was also modified in csla2-1 mucilage. Taken together, our results demonstrate that glucomannans synthesized by CSLA2 are involved in modulating the structure of adherent mucilage, potentially through altering cellulose organization and crystallization.Mannan polysaccharides are a complex set of hemicellulosic cell wall polymers that are considered to have both structural and storage functions. Based on the particular chemical composition of the backbone and the side chains, mannan polysaccharides are classified into four types: pure mannan, glucomannan, galactomannan, and galactoglucomannan (Moreira and Filho, 2008;Wang et al., 2012;Pauly et al., 2013). Each of these polysaccharides is composed of a b-1,4-linked backbone containing Man or a combination of Glc and Man residues. In addition, the mannan backbone can be substituted with side chains of a-1,6-linked Gal residues. Mannan polysaccharides have been proposed to cross link with cellulose and other hemicelluloses via hydrogen bonds (Fry, 1986;Iiyama et al., 1994;Obel et al., 2007;Scheller and Ulvskov, 2010). Furthermore, it has been reported that heteromannans with different levels of substitution can interact with cellulose in diverse ways (Whitney et al., 1998). Together, these observations indicate the complexity of mannan polysaccharides in the context of cell wall architecture.CELLULOSE SYNTHASE-LIKE A (CSLA) enzymes have been shown to have mannan synthase activity in vitro. These enzymes polymerize the b-1,4-linked backbone of mannans or glucomannans, depending on the substrates (GDP-Man and/or GDP-Glc) provided (Richmond and Some...

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“…CELLULOSE SYNTHASE5 (CESA5) was found to be involved in cellulose synthesis (Sullivan et al, 2011), while MUCILAGE-MODIFIED4/RHAMNOSE SYNTHESIS2 (MUM4/RHM2) encodes a UDP-Rha synthase (Usadel et al, 2004;Western et al, 2004;Oka et al, 2007). The mum2, atsbt1.7, atbxl1, pmei6, fly1, and per36 mutants were found to be defective in pectin modification (Dean et al, 2007;Macquet et al, 2007b;Rautengarten et al, 2008;Arsovski et al, 2009;Saez-Aguayo et al, 2013;Voiniciuc et al, 2013) or in the degradation of the outer cell wall of the outer integument (Kunieda et al, 2013), all of which show a mucilage-release defect.…”

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confidence: 99%

GALACTURONOSYLTRANSFERASE-LIKE5 Is Involved in the Production of Arabidopsis Seed Coat Mucilage

et al. 2013

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The function of a putative galacturonosyltransferase from Arabidopsis (Arabidopsis thaliana; At1g02720; GALACTURONOSYLTRANSFERASE-LIKE5 [AtGATL5]) was studied using a combination of molecular genetic, chemical, and immunological approaches. AtGATL5 is expressed in all plant tissues, with highest expression levels in siliques 7 DPA. Furthermore, its expression is positively regulated by several transcription factors that are known to regulate seed coat mucilage production. AtGATL5 is localized in both endoplasmic reticulum and Golgi, in comparison with marker proteins resident to these subcellular compartments. A transfer DNA insertion in the AtGATL5 gene generates seed coat epidermal cell defects both in mucilage synthesis and cell adhesion. Transformation of atgatl5-1 mutants with the wild-type AtGATL5 gene results in the complementation of all morphological phenotypes. Compositional analyses of the mucilage isolated from the atgatl5-1 mutant demonstrated that galacturonic acid and rhamnose contents are decreased significantly in atgatl5-1 compared with wild-type mucilage. No changes in structure were observed between soluble mucilage isolated from wild-type and mutant seeds, except that the molecular weight of the mutant mucilage increased 63% compared with that of the wild type. These data provide evidence that AtGATL5 might function in the regulation of the final size of the mucilage rhamnogalacturonan I.

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PECTIN METHYLESTERASE INHIBITOR6 Promotes Arabidopsis Mucilage Release by Limiting Methylesterification of Homogalacturonan in Seed Coat Epidermal Cells

Cited by 126 publications

References 67 publications

SALT-OVERLY SENSITIVE5 Mediates Arabidopsis Seed Coat Mucilage Adherence and Organization through Pectins

SALT-OVERLY SENSITIVE5 Mediates Arabidopsis Seed Coat Mucilage Adherence and Organization through Pectins

CELLULOSE SYNTHASE-LIKE A2, a Glucomannan Synthase, Is Involved in Maintaining Adherent Mucilage Structure in Arabidopsis Seed

GALACTURONOSYLTRANSFERASE-LIKE5 Is Involved in the Production of Arabidopsis Seed Coat Mucilage

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