External association of hordothionin with protein bodies in mature barley

Carbonero, Pilar; Garcı́a-Olmedo, Francisco; Hernández-Lucas, C.

doi:10.1021/jf60228a018

Cited by 13 publications

(3 citation statements)

References 12 publications

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“…It was found in the 'microsome' and 'membrane' fractions of plants containing the pB c~ or pCl~ construct, suggesting that the AP is not involved in sorting and that the signal for intracellular retention must be in the mature protein domain. The presence of HTH in the membrane fraction is in agreement with sucrose gradient centrifugation experiments performed on barley endosperm where the HTH was found to cosediment with the ER and membranes of the protein bodies [4,34] and immunogold labelling performed on barley leaves which indicated that the (type 2) thionin was present in the vacuoles [36] and cell wall [2]. These type 2 thionins were also not found in the intracellular spaces of barley leaves [16].…”

Section: Discussionsupporting

confidence: 85%

Expression of biologically active hordothionins in tobacco. Effects of pre- and pro-sequences at the amino and carboxyl termini of the hordothionin precursor on mature protein expression and sorting

et al. 1994

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Hordothionins (HTHs) are small anti-bacterial proteins present in barley endosperm which are processed from larger precursor proteins, consisting of an amino-terminal signal peptide (SP), the mature highly basic HTH and a carboxy-terminal acidic peptide (AP). Different HTH precursor proteins were expressed in tobacco to study the effects of the pre-sequences (SP) and pro-sequences (AP) on expression, processing, sorting and biological activity and hence the feasibility of engineering bacterial disease resistance into crops which lack these proteins. Maximum HTH expression levels of approximately 0.7% (11 mumol/kg) of total soluble protein in young tobacco leaves were obtained using a semi-synthetic gene construct encoding a complete chimaeric HTH precursor protein. Tenfold lower HTH expression levels (maximum 1.3 mumol/kg) were obtained using synthetic gene constructs without the AP-coding sequence and no expression was found in plants containing synthetic HTH gene constructs without SP- and AP-coding sequences. In both cases where expression was found, the precursors were apparently correctly processed, although the HTH produced in plants containing a construct without AP sequence appeared to be slightly modified. No effect on plant phenotype was observed. Localization studies indicated that the HTH was in identical fractions of plants expressing the two different precursors, albeit at a different ratio, and was not secreted into the intercellular spaces of leaves or culture medium by protoplasts. Our results indicated that the AP is not involved in sorting and suggested that it might facilitate transport through membranes. The in vitro toxicity of HTH isolated from transgenic tobacco plants expressing the two different precursor proteins for the bacterial plant pathogen Clavibacter michiganensis subsp. michiganensis appeared similar to that of the HTH purified from barley endosperm.

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Section: Discussionsupporting

confidence: 85%

Expression of biologically active hordothionins in tobacco. Effects of pre- and pro-sequences at the amino and carboxyl termini of the hordothionin precursor on mature protein expression and sorting

et al. 1994

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“…In sucrose gradient centrifugation, the hordothionin was found to cosediment with an ER marker and the protein bodies, but could be extracted from the particulate fraction without disturbing the protein body integrity [20,75]. Immunogold labelling of thin sections from barley endosperm also indicated specific labelling in the periphery of the protein bodies [ 21].…”

Section: Synthesis and Processing Of Thioninsmentioning

confidence: 98%

Thionins: properties, possible biological roles and mechanisms of action

1994

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Thionins are low-molecular-weight proteins (M(r) ca. 5000) occurring in seeds, stems, roots and leaves of a number of plant species. The different members of this family of plant proteins show both sequence and structural homology, and are toxic to bacteria, fungi, yeasts and various naked cells in vitro. Toxicity requires an electrostatic interaction of the positively charged thionin with the negatively charged phospholipids making up the membrane, followed by either pore formation or a specific interaction with a certain lipid domain. This domain might be composed of phosphoinositides, which mediate transduction of environmental signals in eukaryotes. Their in vitro toxicity to plant pathogenic bacteria and fungi could reflect a direct role in plant defence, although, in view of the many divergent activities displayed by thionins both in vitro and in vivo, a biological role other than inhibition of microbial growth is equally plausible.

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“…At least two processing steps, one co-translational and the other post-translational, were postulated on the basis of these observations. Preliminary fractionation studies carried out both with the dry mature endosperm (Carbonero et al, 1980) and with developing tissue (Ponz et al, 1983) indicated that the thionins were in the particulate fraction in a labile association that could be disrupted by increasing the salt concentration or with non-ionic detergents. Under the conditions used by Ponz et al (1983), the thionins roughly co-sedimented with cytochrome C reductase (NADPH, antimycin Aresistant), a marker of the endoplasmic reticulum.…”

Section: Endosperm Thioninsmentioning

confidence: 99%

The Thionins: A Protein Family That Includes Purothionins, Viscotoxins And Crambins

Garcia-Olmedo,

Rodriguez-Palenzuela,

Hernandez-Lucas

et al. 1990

Oxford Surveys of Plant Molecular and Cell Biology

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The toxic properties of mistletoes, which were responsible for a famous death in Nordic mythology, can be ascribed to different components, including the toxic lectin viscumin (Olsnes et al., 1982) and a mixture of small basic proteins, which were first isolated by Winterfeld and Bijl (1949) and designated “viscotoxin”. The viscotoxins produce hypotension and other effects at sublethal doses (Samuelsson, 1974).

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External association of hordothionin with protein bodies in mature barley

Cited by 13 publications

References 12 publications

Expression of biologically active hordothionins in tobacco. Effects of pre- and pro-sequences at the amino and carboxyl termini of the hordothionin precursor on mature protein expression and sorting

Expression of biologically active hordothionins in tobacco. Effects of pre- and pro-sequences at the amino and carboxyl termini of the hordothionin precursor on mature protein expression and sorting

Thionins: properties, possible biological roles and mechanisms of action

The Thionins: A Protein Family That Includes Purothionins, Viscotoxins And Crambins

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