Multiple isozymes of endo-β-d-mannanase in dry and imbibed seeds

Dirk, Lynnette M.A.; Griffen, Alison M.; Downie, Bruce; Bewley, J. Derek

doi:10.1016/0031-9422(95)00296-j

Cited by 35 publications

(38 citation statements)

References 21 publications

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“…Northern hybridizations with man A-and man B-specific probes showed that mRNA transcripts for both cDNAs were present during the same periods of bean germination, with expression peaking 20 days after imbibition of water. Activity and mRNA levels appeared to be tightly coordinated and unlike the reports of Dirk et al (1995) they stated that enzyme activity did not exist in grains prior to germination. Thus, transcripts of the enzyme were not detected during grain maturation or in other tissues of the plant (roots, leaves, stems, flowers).…”

Section: Molecular and Biochemical Characterisation Of Polysaccharidecontrasting

confidence: 73%

“…Dirk et al, (1995) reported multiple isozymes of the enzyme in dry and imbibed seeds while Giorgini and Comoli (1996) measured the effect of growth regulators on the activity of the enzyme during germination. The first molecular characterisation was reported by Marraccini et al (2001) who cloned and sequenced two endo-β-mannanase cDNAs (man A and man B) from germinating coffee grains (Coffea arabica L.).…”

Section: Molecular and Biochemical Characterisation Of Polysaccharidementioning

confidence: 99%

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Coffee carbohydrates

Redgwell

Fischer

2006

Braz. J. Plant Physiol.

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This review summarises recent advances in the chemistry, physiology and molecular properties of coffee carbohydrates with a particular focus on the cell wall polysaccharides. The results of detailed chemical studies have demonstrated novel structural features of both the galactomannans and the arabinogalactan polysaccharides of the green and roasted coffee bean. For the first time immunological probes based on monoclonal antibodies for specific polysaccharide epitopes were used to reveal the patterns of distribution of the galactomannans, arabinogalactans and pectic polysaccharides in the coffee bean cell wall. Finally, the results of physiological and molecular studies are presented which emphasise the growing awareness of the potential role the metabolic status of the green bean may play in final coffee beverage quality. Key words: Coffea, cell wall, beverage quality, seed. Carboidratos do café:Este artigo sumariza os mais recentes desenvolvimentos nas áreas de química, fisiologia e propriedades moleculares dos carboidratos do café, com um particular interesse nos polisacarídeos presentes nas paredes celulares. Os resultados dos estudos químicos detalhados demonstraram novas características estruturais tanto nos galactomananos como nos polissacarídeos dos arabinogalactanos do grão de café verde ou torrado. Pela primeira vez, estudos imunológicos baseados em anticorpos monoclonais foram usados para revelar a distribuição dos galactomananos, dos arabinogalactanos e dos polissacarídeos pectídicos na parede celular do grão de café. Finalmente, os resultados dos estudos fisiológicos e moleculares são apresentados de maneira a sublinhar a influência do status metabólico do grão verde do café na qualidade final da bebida. Palavras-chave: Coffea, parede celular, qualidade da bebida, semente.

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Section: Molecular and Biochemical Characterisation Of Polysaccharidecontrasting

confidence: 73%

Section: Molecular and Biochemical Characterisation Of Polysaccharidementioning

confidence: 99%

Coffee carbohydrates

Redgwell

Fischer

2006

Braz. J. Plant Physiol.

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“…; Nonogaki and Morohashi, 1996), may have been detectable in our assays, even though the assay itself (reducing sugar release) is less sensitive than the viscometric assay used by others. Lettuce cultivars differ in endo-p-mannanase abundance and isozyme complements (Dirk et al, 1995); however, when we used our methods to prepare extracts from cv Grand Rapids (used in other studies), results similar to those presented here for cv Pacific were observed (data not shown). In any case, our study has demonstrated a cell wall-bound endo-p-mannanase activity that, to our knowledge, has not been reported previously and is present prior to radicle emergente.…”

Section: Sc Ussl Onsupporting

confidence: 61%

“…However, cell wall endo-P-mannanase activity described here is clearly present prior to radicle emergence (Table I) but is tightly bound to the cell walls and likely would not have been included in soluble extracts characterized previously. The wall-bound and soluble activities may represent different isozymes, since multiple isoforms of endo-p-mannanase have been reported in many seeds, including lettuce (Dulson and Bewley, 1989;Dirk et al, 1995;Nonogaki et al, 1995). In contrast to previous reports, we found that soluble extracts prepared from endosperms excised from seeds prior to radicle emergence exhibited LBG-hydrolyzing activity (Table I).…”

Section: Sc Ussl Oncontrasting

confidence: 55%

Endo-β-Mannanase Activity Present in Cell Wall Extracts of Lettuce Endosperm prior to Radicle Emergence

1997

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Lettuce (Lactuca safiva 1.) endosperm cell walls isolated prior to radicle emergence underwent autohydrolysis, the rate of which was correlated with whether radicle emergence would subsequently occur. Extraction of endosperm cell walls with 6 M LiCl suppressed autohydrolysis, and the desalted extract possessed activity that was capable of hydrolyzing purified locust bean galactomannan but not arabinogalactan, carboxymethylcellulose, glucomannan, polygalacturonic acid, tomato galactomannan, or native lettuce endosperm cell walls. Some hydrolytic activity was detected on endosperm cell walls if they were modified by partia1 trifluoroacetic acid hydrolysis or pretreatment with guanidinium thiocyanate. I n extended incubations the cell wall enzyme extract released only large molecular m a s fragments from locust bean galactomannan, indicating primarily endo-activity. Galactomannan-hydrolyzing activity in the cell wall extract increased as a function of imbibition time and was greatest just prior to radicle emergence. Thermoinhibition (imbibition at 32OC) or treatment with abscisic acid at a temperature optimal for germination (25'C) suppressed both germination and endosperm cell wall mannanase activity, whereas alleviation of thermoinhibition with gibberellic acid was accompanied by significant enhancement of mannanase activity. We conclude that a cell wall-bound endo-p-mannanase is expressed in lettuce endosperm prior t o radicle emergence and is regulated by the same conditions that govern germination.

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“…Development of endo-P-mannanase activity is localized in the endosperm cap prior to radicle emergence and is reported to be inhibited by far-red light and ABA, which also block radicle emergence Nonogaki and Morohashi, 1996). There are multiple isozymes of endo-pmannanase in germinating tomato seeds (Dirk et al, 1995;Nonogaki et al, 1995;Toorop et al, 1996), but only a single isozyme appears in the endosperm cap prior to radicle emergence (Nonogaki and Morohashi, 1996). An attractive hypothesis, therefore, is that & of tomato seeds is related to the extent of weakening of the endosperm cap, which in turn is dependent primarily on the development of endo-P-mannanase activity, although other enzymes may also be involved (Sanchez et al, 1986;Leubner-Metzger et al, 1995Black, 1996).…”

mentioning

confidence: 99%

Endo-β-Mannanase Activity from Individual Tomato Endosperm Caps and Radicle Tips in Relation to Germination Rates

Still

Bradford

1997

Plant Physiology

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~ ~ ~~Endo-P-mannanase is hypothesized to be a rate-limiting enzyme in endosperm weakening, which is a prerequisite for radicle emergente from tomato (Lycopersicon esculentum Mill.) seeds. Using a sensitive, single-seed assay, we have measured mannanase activity diffusing from excised tomato endosperm caps following treatments that alter the rate or percentage of radicle emergence. Most striking was the 100-to more than 10,000-fold range of mannanase activity detected among individual seeds of highly inbred tomato lines, which would not be detected in pooled samples. In some cases a threshold-type relationship between mannanase activity and radicle emergence was observed. However, when radicle emergence was delayed or prevented by osmoticum or abscisic acid, the initial increase in mannanase activity was unaffected or even enhanced. Partially dormant seed lots displayed a bimodal distribution of activity, with low activity apparently associated with dormant seeds in the population. Gibberellin-and abscisic acid-deficient mutant seeds exhibited a wide range of mannanase activity, consistent with their variation in hormonal sensitivity. Although the presence of mannanase activity in the endosperm cap is consistently associated with radicle emergence, it is not the sole or limiting factor under all conditions.Even though tomato (Lycopersicon esculentum Mill.) is self-pollinating and cultivars are highly homozygous genetically, germination behavior varies considerably among individual seeds. We have developed a population-based hydrotime model that accurately describes germination time courses in response to environmental and hormonal factors (Bradford, 1990(Bradford, , 1995(Bradford, , 1996 Bradford, 1990, 1994; Bradford, 1992, 1993). This model is based on the assumption that individual seeds vary in their sensitivity to these factors and particularly in the sensitivity of radicle emergence to +. If the +, , is higher (more positive) than the actual seed +, radicle emergence will not occur. The lower (more negative) the & for radicle emergente relative to the ambient +, the more rapid germination will be. The distribution of Ic., values within the seed population therefore determines both the rate and final percentage of germination. Environmental and hormonal fac- (Ni and Bradford, 1993;Dutta and Bradford, 1994;Bradford, 1995Bradford, , 1996.The population-based hydrotime model can quantify and describe seed germination patterns, but it does not identify the physiological or biochemical basis of +, , .

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Multiple isozymes of endo-β-d-mannanase in dry and imbibed seeds

Cited by 35 publications

References 21 publications

Coffee carbohydrates

Coffee carbohydrates

Endo-β-Mannanase Activity Present in Cell Wall Extracts of Lettuce Endosperm prior to Radicle Emergence

Endo-β-Mannanase Activity from Individual Tomato Endosperm Caps and Radicle Tips in Relation to Germination Rates

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