In flowers, some parts undergo CD and fall, like stamina and petals of the corolla. The petal senescence is a controlled event; a signal for the abscission of the petals is pollination in the long life flowers (beyond the 2 days) or an endogenous program in the short life flowers (1-2 day). Ethylene, cytokinins and abscisic acid seem to regulate petal senescence. Alifatic polyamines (PAs) have a role in the plants cellular division, growth and senescence. The corolla of flower of Nicotiana has been chosed as a model, whose life phases, described during its development, senescence and death, are defined by many parameters. Key transition events mark the no-return point, identified by changes in water, pigment and protein content, protease activity, DNA laddering and by the formation of a cell ring of reduced mechanical resistance. Under natural conditions the dead corolla remains on the thalamus to protect the developing ovary and only at a very late stage the corolla naturally falls entire, from the abscission ring. The senescence events show an acropetal gradient and the corolla has been divided into three parts (proximal, medial and distal) and studied during its life span also at sub-cellular levels. The target of this study was to delay the senescence of the corolla, by supplying spermine and to understand its mechanism of action. In Nicotiana PAs are free or bound to hydroxycinnamic acids and proteins; PAs are conjugated to endoglutamines of proteins by catalysis of transglutaminase (TGase), thus forming either intra- and inter-molecular bridges. In animals the post-translational modification of proteins by TGase appears a relevant factor in the CD. In Nicotiana this enzyme has been immuno detected both into the entire corolla and in all its three parts, with three antibodies raised either against TGase of animal or plant origin. All the antibodies recognised a main band of 58 kDa and one of 61 kDa, whereas some antibodies recognised also a band of 38 kDa which disappeared during senescence. The 58 kDa band has been detected in microsomal, plastidial and cell wall enriched fractions; a 52 kDa only in the soluble fraction. The tissue printing immunoassay confirmed the presence of a soluble TGase only at the abscission ring. The activity of TGase was tested by glutamyl-derivative analysis, by using a specific modified substrate (His6-X press-GFP) and PA cross-link to endogenous proteins. The activity during the corolla life span, without to add exogenous Ca2+, was low in the developmental phases, increased at senescence with the maximum at the no-return point and with a final decrease at the latest stages. In the three corolla parts, the maximum of the TGase activity is progressively shifted towards the distal part; this wave-like pattern precedes a similar wave of senescence macroscopical events. The TGase activity in the microsomal enriched fraction has a trend similar to that of the entire cell; in the soluble one, it was absent in the developmental stages and increased at senescence only in the proximal corolla part. By contrast, the activity in the plastid enriched fraction is generally high with a progressive increase after the flower completed its development. The activity in the cell walls is always present, prevalently into the distal part where it progressively increased. A role for TGase in corolla development and CD is proposed.

“ Programmed cell death in plants: flower corolla as an example.”. Atti del 52 Convegno GEI. 52° Convegno GEI (Gruppo Embriologico Italiano). Otranto. 06-09 Giugno 2006. (pp. 15). OTRANTO: .

SERAFINI FRACASSINI, DONATELLA;DEL DUCA, STEFANO
2006

Abstract

In flowers, some parts undergo CD and fall, like stamina and petals of the corolla. The petal senescence is a controlled event; a signal for the abscission of the petals is pollination in the long life flowers (beyond the 2 days) or an endogenous program in the short life flowers (1-2 day). Ethylene, cytokinins and abscisic acid seem to regulate petal senescence. Alifatic polyamines (PAs) have a role in the plants cellular division, growth and senescence. The corolla of flower of Nicotiana has been chosed as a model, whose life phases, described during its development, senescence and death, are defined by many parameters. Key transition events mark the no-return point, identified by changes in water, pigment and protein content, protease activity, DNA laddering and by the formation of a cell ring of reduced mechanical resistance. Under natural conditions the dead corolla remains on the thalamus to protect the developing ovary and only at a very late stage the corolla naturally falls entire, from the abscission ring. The senescence events show an acropetal gradient and the corolla has been divided into three parts (proximal, medial and distal) and studied during its life span also at sub-cellular levels. The target of this study was to delay the senescence of the corolla, by supplying spermine and to understand its mechanism of action. In Nicotiana PAs are free or bound to hydroxycinnamic acids and proteins; PAs are conjugated to endoglutamines of proteins by catalysis of transglutaminase (TGase), thus forming either intra- and inter-molecular bridges. In animals the post-translational modification of proteins by TGase appears a relevant factor in the CD. In Nicotiana this enzyme has been immuno detected both into the entire corolla and in all its three parts, with three antibodies raised either against TGase of animal or plant origin. All the antibodies recognised a main band of 58 kDa and one of 61 kDa, whereas some antibodies recognised also a band of 38 kDa which disappeared during senescence. The 58 kDa band has been detected in microsomal, plastidial and cell wall enriched fractions; a 52 kDa only in the soluble fraction. The tissue printing immunoassay confirmed the presence of a soluble TGase only at the abscission ring. The activity of TGase was tested by glutamyl-derivative analysis, by using a specific modified substrate (His6-X press-GFP) and PA cross-link to endogenous proteins. The activity during the corolla life span, without to add exogenous Ca2+, was low in the developmental phases, increased at senescence with the maximum at the no-return point and with a final decrease at the latest stages. In the three corolla parts, the maximum of the TGase activity is progressively shifted towards the distal part; this wave-like pattern precedes a similar wave of senescence macroscopical events. The TGase activity in the microsomal enriched fraction has a trend similar to that of the entire cell; in the soluble one, it was absent in the developmental stages and increased at senescence only in the proximal corolla part. By contrast, the activity in the plastid enriched fraction is generally high with a progressive increase after the flower completed its development. The activity in the cell walls is always present, prevalently into the distal part where it progressively increased. A role for TGase in corolla development and CD is proposed.
2006
Atti del 52 Convegno GEI. 52° Convegno GEI (Gruppo Embriologico Italiano). Otranto. 06-09 Giugno 2006
15
15
Serafini Fracassini D.; Della Mea M.; De Filippis F.; Genovesi V.; Del Duca S.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/43800
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