Ultrastructural changes of chloroplasts in detached parsley leaves yellowing in darkness and the influence of kinetin on that process

Młodzianowski, Fortunat; Ponitka, A.

doi:10.1016/s0044-328x(73)80147-3

Cited by 21 publications

(7 citation statements)

References 22 publications

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“…The fact that such a large proportion of the aminopeptidase activity is associated with the chloroplast supports the notion that proteins can be degraded in the chloroplast. Despite the lack of evidence for a chloroplast-located endopeptidase, ultrastructural studies of chloroplast senescence have shown major disruption of chloroplast lamellae and stroma before degeneration of the outer double membrane (16,21). To be effective in protein degradation, however, aminopeptidases appear to require the presence of an endopeptidase.…”

Section: Discussionmentioning

confidence: 99%

Intracellular Localization of Peptide Hydrolases in Wheat (Triticum aestivum L.) Leaves

Waters¹,

Noble²,

Dalling³

1982

Plant Physiol.

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Protoplasts from 8-to 9-day-old wheat (Triticum aestivum L.) leaves were used to isolate organelles which were examined for their contents of peptide hydrolase enzymes and, in the case of vacuoles, other acid hydrolases. High yields of intact chloroplasts were obtained using both equilibrium density gradient centrifugation and velocity sedimentation centrifugation on sucrose-sorbitol gradients. Aminopeptidase activity was found to be distributed, in approximately equal proportions, between the chloroplasts and cytoplasm. Leucyltyrosine dipeptidase was mainly found in the cytoplasm, although about 27% was associated with the chloroplasts. Vacuoles shown to be free from Ceilulysin contamination contained all of the protoplast carboxypeptidase and hemoglobin-degrading activities. The acid hydrolases, phosphodiesterase, acid phosphatase, a-mannosidase, and fP-N-acetylgucosamidase were found in the vacuole to varying degrees, but no f8-glucosidase was localized in the vacuole.Studies of protein degradation in plant tissues have demonstrated the existence of a diverse group of peptide hydrolase enzymes. Protein degradation has been envisaged as a process initiated by endopeptidase action and continued through the action of exopeptidases, including aminopeptidases, carboxypeptidase, and di-and tri-peptidases to eventually release amino acids for storage and/or transport (24). Characterization of these enzymes (5,15,22,29) has shown that, despite their common role in protein breakdown, they have few similarities with respect to the conditions required for optimal in vitro activity. These differences, particularly differences in optimum assay pH, have led to suggestions of enzyme compartmentalization as a means of regulating protein degradation, since the plant cell contains a number of localized pH zones by virtue of its various organelles.Although acid proteinases are known to be localized in leaf vacuoles (3,11), no other peptide hydrolases have been reported there. Carboxypeptidase activity has been located in protein bodies from the cotyledons of germinating mung beans (7,27) and in vacuoles prepared from the endosperm tissue of 4-d-old castor bean seedlings (18) but has not been reported in vacuoles isolated from leaf tissue. In a previous publication (30), we examined the patterns of activity of a number of enzymes during senescence of the wheat plant. The present study was undertaken to examine the spatial relationship between these enzymes, which include acid proteinase, amino-and carboxypeptidases, and an alkaline dipep- MATERIALS AND METHODS Plant Material. Wheat seeds (Triticum aestivum cv. Egret) were imbibed for 24 h prior to being transferred to 34-x 29-x 6-cm trays containing a compost soil mixture. Plants were grown in a glasshouse under natural daylength and light-intensity conditions. Plants were watered daily without additional nutrients.Protoplast Preparation. Primary leaves from 8-to 9-d-old wheat seedlings were used to isolate protoplasts. The lower epidermis was removed, and the leaves wer...

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Section: Discussionmentioning

confidence: 99%

Intracellular Localization of Peptide Hydrolases in Wheat (Triticum aestivum L.) Leaves

Waters¹,

Noble²,

Dalling³

1982

Plant Physiol.

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“…The degradations of chloroplasts are extensive and sequential (De Vecchi 1971, Butler and Simon 1971, Mlodzianowski and Ponitka 1973. Changes in the size, shape and fine structure of chloroplasts isolated from senescing leaves have been observed (Dodge 1970).…”

Section: Introductionmentioning

confidence: 99%

Changes in the Ability of Photophosphorylation and Activities of Surface‐Bound Adenosine Triphosphatase and Ribulose Diphosphate Carboxylase of Chloroplasts Isolated from the Barley Leaves Senescing in Darkness

Biswal

Mohanty

1978

Physiologia Plantarum

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Dark induced aging of detached primary leaves of 11-day-old barley seedlings brings about a significant decline in the rates of ferricyanide |Fe(CN)jJ'" reduction and photophosphorylations of isolated chloroplasts. Ferricyanide-supported noncyclic photophosphorylation is somewhat more susceptible to leaf aging than phenazine methosulfate (PMS)-supported cyclic phosphorylation. Non-latent membrane-bound adenosine triphosphatase (ATPase) and ribulosediphosphate carboxylase (RuDPCase) lose about half of their initial activities after 24 h, while during this period the electron transport and photophosphorylation activities are much less affected. Also, the loss of RuDPCase is almost complete, while chloroplasts still exhibit a significant level of iFe(CN)^]'" reduction and photophosphorylations after 7 days of dark incubation. This would suggest that the enzymatic dark reactions are more sensitive to aging stress than the primary photochemical reactions of chloroplasts.Studies on the effect of divalent cations such as Mg^+ and Ca^+ on non-latent ATPase activity revealed that the dark stressed aging of detached leaves brings about a time dependent alteration in the response of this enzyme to Mg-'^, but not to Ca^+. The former showed inhibitory as well as stimulatory response, whereas the latter always caused the usual stimulation. Addition of kinetin (50 M) ensured retention of |Fe(CN)J^-reduction, photophosphorylations and RuDPCase activity in chloroplasts during leaf aging, but it failed to preserve the initial loss in the activity of the non-activated membrane-bound ATPase.

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“…This characteristic feature of aged cultures of Scenedesmus is in contrast to the changes normally observed in the ultrastructure of higher plant chloroplasts under senescent conditions. Both natural and in vitro senescence has been reported (Barton 1966, De Vecchi 1971, Mittelheuser and Van Steveninck 1971, MIodzianowski and Ponitka 1973, Shaw and Manocha 1965 to cause shrinkage in ehloroplast volume, breakdown of the stroma thylakoids, disorganization of grana by swelling and increase in the number and volume of the plastoglobules.…”

Section: Resultsmentioning

confidence: 99%

Changes in the Reactivity of the Photosynthetic Apparatus in Heterotrophic Ageing Cultures of Scenedesmus obliquus

Kulandaivelu¹,

Senger²

1976

Physiologia Plantarum

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Ultrastructural changes of the chloroplast which occur parallel to the decay of photosynthetic capacity during the heterotrophic ageing of Scenedesmus cells have been studied. A gradual disappearance of the starch grains took place as the nutrients in the growth medium were depleted. Accompanying this change was a deterioration in the structure of the cytoplasm coupled with a concomitant granular appearance. At the same time thylakoid structures were not only well preserved but accumulated more material. This resulted in an increasing number of stacked thylakoids and a thickening of the membranes.

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Ultrastructural changes of chloroplasts in detached parsley leaves yellowing in darkness and the influence of kinetin on that process

Cited by 21 publications

References 22 publications

Intracellular Localization of Peptide Hydrolases in Wheat (Triticum aestivum L.) Leaves

Intracellular Localization of Peptide Hydrolases in Wheat (Triticum aestivum L.) Leaves

Changes in the Ability of Photophosphorylation and Activities of Surface‐Bound Adenosine Triphosphatase and Ribulose Diphosphate Carboxylase of Chloroplasts Isolated from the Barley Leaves Senescing in Darkness

Changes in the Reactivity of the Photosynthetic Apparatus in Heterotrophic Ageing Cultures of Scenedesmus obliquus

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