Development Of Chromoplasts Research Articles

ORANGE gene positively regulates chromoplast formation and carotenoid accumulation in Osmanthus fragrans

Sweet osmanthus (Osmanthus fragrans) cultivar from Aurantiacus Group shows orange or orange-red flower color due to the accumulation of abundant carotenoids in the petals. Orange (Or) gene has been functionally characterized in the formation of plant chromoplasts and carotenoid accumulation in several species. However, whether Or gene from sweet osmanthus plays essential role in the formation of plant chromoplasts is not clear. In this study, we isolated Or homologous gene OfOr from sweet osmanthus by transcriptome homology search. The protein encoded by the gene has two transmembrane domains and a zinc finger domain, and is co-localized with the chloroplasts. Transmission electron microscopy analysis of the petal tissues of sweet osmanthus showed that the chromoplast volume, the plastoglobule number and volume increased significantly with petal development, accompanied by an increase in the expression level of OfOr. Correlation analysis showed that the development of chromoplasts was significantly positively correlated with the expression pattern of OfOr. In addition, after stable overexpression of OfOr in tomato (Solanum lycopersicum), it was found that the transgenic tomato fruits exhibited significantly higher redness, yellowness and chroma, as well as an increased distribution of carotenoids in the pulp cells, with total carotenoid content significantly higher than that of wild type. In summary, our study indicate that OfOr positively regulates chromoplast formation and carotenoid accumulation. This study also further reveals that OfOr can be used as a novel genetic tool to increase the accumulation of carotenoids and improve the coloring of colored organs in crops and ornamental plants.

Carotenoid Profile, Antioxidant Capacity, and Chromoplasts of Pink Guava (Psidium guajava L. Cv. 'Criolla') during Fruit Ripening.

Pigments of pericarp and pulp of pink guava (Psidium guajava L. cv. 'Criolla') were investigated to elucidate the profile and the accumulation of main carotenoids during four stages of fruit ripening by using HPLC-DAD and APCI-MS/MS analysis. Seventeen carotenoids were identified, and changes in their profile during fruit ripening were observed. The carotenoids all-trans-β-carotene, 15-cis-lycopene, and all-trans-lycopene were present in all ripening stages, but all-trans-lycopene was found to be predominant (from 63% to 92% of total carotenoids) and responsible for the high lipophilic antioxidant capacity determined by spectrophotometric assays. By using light and transmission electron microscopy, the development of chromoplasts in pericarp and pulp was demonstrated. The accumulation of all-trans-lycopene and all-trans-β-carotene coincided with the development of large crystals; the chromoplasts of pink guava belong, therefore, to the crystalline type.

Cytological and molecular characterization of carotenoid accumulation in normal and high-lycopene mutant oranges

Ripe Cara Cara sweet orange contains 25 times as much carotenoids in flesh as Newhall sweet orange, due to high accumulation of carotenes, mainly phytoene, lycopene and phytofluene. Only yellow globular chromoplasts were observed in Newhall flesh. Distinct yellow globular and red elongated crystalline chromoplasts were found in Cara Cara but only one type of chromoplast was present in each cell. The red crystalline chromoplasts contained lycopene as a dominant carotenoid and were associated with characteristic carotenoid sequestering structures. The increased accumulation of linear carotenes in Cara Cara is not explained by differences in expression of all 18 carotenogenic genes or gene family members examined, or sequence or abundance of mRNAs from phytoene synthase (PSY) and chromoplast-specific lycopene β-cyclase (CYCB) alleles. 2-(4-Chlorophenylthio)-triethylamine hydrochloride (CPTA) enhanced lycopene accumulation and induced occurrence of red crystalline chromoplasts in cultured Newhall juice vesicles, indicating that carotenoid synthesis and accumulation can directly affect chromoplast differentiation and structure. Norflurazon (NFZ) treatment resulted in high accumulation of phytoene and phytofluene in both oranges, and the biosynthetic activity upstream of phytoene desaturase was similar in Newhall and Cara Cara. Possible mechanisms for high carotene accumulation and unique development of red crystalline chromoplasts in Cara Cara are discussed.

Regulation of Carotenoid Biosynthesis During Fruit Development.

Carotenoids are recognized as the main pigments in most fruit crops, providing colours that range from yellow and pink to deep orange and red. Moreover, the edible portion of widely consumed fruits or their derived products represent a major dietary source of carotenoids for animals and humans. Therefore, these pigments are crucial compounds contributing to fruit aesthetic and nutritional quality but may also have protecting and ecophysiological functions in coloured fruits. Among plant organs, fruits display one of the most heterogeneous carotenoids patterns in terms of diversity and abundance. In this chapter a comprehensive list of the carotenoid content and profile in the most commonly cultivated fleshy fruits is reported. The proposed fruit classification systems attending to carotenoid composition are revised and discussed. The regulation of carotenoids in fruits can be rather complex due to the dramatic changes in content and composition during ripening, which are also dependent on the fruit tissue and the developmental stage. In addition, carotenoid accumulation is a dynamic process, associated with the development of chromoplasts during ripening. As a general rule, carotenoid accumulation is highly controlled at the transcriptional level of the structural and accessory proteins of the biosynthetic and degradation pathways, but other mechanisms such as post-transcriptional modifications or the development of sink structures have been recently revealed as crucial factors in determining the levels and stability of these pigments. In this chapter common key metabolic reactions regulating carotenoid composition in fruit tissues are described in addition to others that are restricted to certain species and generate unique carotenoids patterns. The existence of fruit-specific isoforms for key steps such as the phytoene synthase, lycopene β-cyclases or catabolic carotenoid cleavage dioxygenases has allowed an independent regulation of the pathway in fruit tissues and a source of variability to create novel activities or different catalytic properties. Besides key genes of the carotenoid pathway, changes in carotenoid accumulation could be also directly influenced by differences in gene expression or protein activity in the pathway of carotenoid precursors and some relevant examples are discussed. The objective of this chapter is to provide an updated review of the main carotenoid profiles in fleshy fruits, their pattern of changes during ripening and our current understanding of the different regulatory levels responsible for the diversity of carotenoid accumulation in fruit tissues.

Specific carotenoids and proteins as prerequisites for chromoplast tubule formation

The effect of inhibitors of carotenoid and protein biosynthesis on the development of tubulous chromoplasts has been investigated inTropaeolum majus andImpatiens noli-tangere by biochemical methods and electron microscopy. (1) Under the influence of norflurazone, a potent inhibitor of carotenoid biosynthesis, colorless flowers are formed in both species, the cells of which contain globulous leukoplasts instead of tubulous chromoplasts. (2) Contrary to this, unpigmented areas of petals ofCaltha palustris (normally with globulous chromoplasts) andNarcissus pseudonarcissus (with membraneous chromoplasts) are not affected in their respective plastid fine structure by norflurazone treatment. (3) CPTA, also affecting carotenoid biosynthesis, leads to the formation of pale pink flowers inTropaeolum, their major pigment being lycopene (normally not present in flowers of this plant). Chromoplast tubules are not formed under the influence of CPTA. Instead, the flower plastids contain osmiophilic globules as well as lycopene crystals and lycopene containing membranes. (4) Cycloheximide, inhibiting cytoplasmic protein biosynthesis, does not affect carotenoid biosynthesis inTropaeolum. It nevertheless abolishes the formation of chromoplast tubules, and also the accumulation of a nucleus-encoded 30 kDa protein that appears to be a major and obligatory component of chromoplast tubules. After CHI treatment, chromoplasts contain globules instead of tubules. (5) Inhibitors of plastid transcription (e.g., rifampicin) or translation (chloramphenicol, lincomycin) do not affect chromoplast fine structure in flowers ofTropaeolum. (6) Tubulous chromoplasts of flowers and fruits of plants from 4 diverse angiosperm classes invariantly contain apolar carotenoids as their main pigments and are devoid of xanthophylls. (7) Taken together, the results of our study strongly suggest that apolar carotenoids as well as specific structural proteins are essential constituents of chromoplast tubules. The data presented agree with a previously proposed model of the molecular fine structure of chromoplast tubules.

The Development of Daffodil Chromoplasts in the Presence of Herbicides SAN 9789 and SAN 9785

The effects of two pyridazinone herbicides (SAN 9789 and SAN 9785) were studied on the fine structure and carotenoid composition during the transformation of chloroplasts into chromoplasts in daffodil (Narcissus poëticus L.) flowers. SAN 9789 caused the absence of big characteristic carotene crystals and the appearance of numerous nonosmiophilic plastoglobuli in chromoplasts. The accumulation of all carotenoids was drastically reduced and the content of carotenes was 40-fold lower than in the control. SAN 9785 caused no gross abnormalities in ultrastructure of chromoplasts. The synthesis of carotenes was partially reduced to about 75%. In spite of this the accumulation of xanthophylls is two times higher than in the control. The interaction between chromoplast ultrastructure and carotenoid composition is discussed.

Chromoplast Development in Daffodil Coronae during Anthesis

The development of membraneous chromoplasts in growing coronae of the daffodil has been investigated fine-structurally and biochemically. Three stages have been selected: Flower buds with greenish prochromoplasts, opening flowers, and open flowers with fully-grown chromoplasts. As there are no cell divisions in these stages, the growth of the coronae is solely due to cell enlargement. The doubling of the projection area of the cells is accompanied by a doubling of chromoplast number per cell. Transition of prochromoplasts to chromoplasts is marked by thylakoid and chlorophyll degradation. Concomitantly, there is a rapid increase in plastidspecific polar lipids and carotenoids, and chromoplast-specific proteins begin to accumulate. However, in the course of these changes, the number of plastid ribosomes diminishes. Whereas their portion among total cellular ribosomes amounts to 10 % in flower buds, plastid ribosomes cannot be detected in coronae with fully developed chromoplasts. Further, although plastid polysomes are present in all developmental stages in green leaves, no plastid polysomes could be detected in coronae of opening or open flowers. Accordingly, no protein synthesis can occur in chromoplasts of the daffodil, contrary to other types of plastids which possess polysomes active in translation. On the basis of these results it is to be supposed that chromoplast-specific proteins in general are coded for in the nucleus and must be imported into developing chromoplasts from the cytoplasm.

Daffodil Chromoplast DNA: Comparison with Chloroplast DNA, Physical Map, and Gene Localization

Abstract In daffodil, development of chloroplasts or chromoplasts is not accompanied by plastid DNA modification. This has been shown by comparing the fragment pattern of different restriction endonucleases, and by the lack of methylation of CCGG sequences. A physical map has been constructed for the plastome using the restriction endonucleases Sal I, Pst I, and Bgl I. The fragments containing the genes for the large subunit of ribulose bisphosphate carboxylase/oxygenase (rbcL), the alpha, beta, and epsilon subunits of the ATP synthase complex (atpA , atpB, atpE ), cytochrome f(petA ), and for the 51 kDa chlorophyll apoprotein of photosystem II (psbB) have been identified. The respective gene locations correspond to those on spinach chloroplast DNA.

Ultrastructural development of plastids in cherry peppers during fruit ripening

The fine structure of plastids in the fruit of cherry peppers was studied during the various stages of ripening. The color change of fruit during ripening is due to the quantitative change of such pigment components as chlorophyll, carotenoid and anthocyanin. Plastid metamorphosis takes place in relationship to the disappearance of chlorophyll and the new formation of carotenoids. The membrane system of plastids degenerates through ripening, although a little differentiation is observed in young plastids of creamy fruits. In parallel wity the color change of fruit from cream to orange, the osmiophilic globules increase in both number and size. As ripening proceeds further, the large osmiophilic globules seem to be gradually transformed into the needle shaped crystalloids of carotenoid pigments which are the remarkable feature of the chromoplasts in red-ripe fruit. The relationship between the development of chromoplasts and the increase and decrease of some pigments is also discussed.

Die Lokalisation der Plastidenchinone und Carotinoide in den Chromoplasten der Petalen von Sarothamnus scoparius (L.) Wimm ex Koch

1. The yellow petals of Sarothamnus are colored by chromoplasts which contain free xanthophylls and carotenoid esters. During development of chromoplasts from young chloroplasts the secondary carotenoids are formed together with plastidquinones of the benzoquinone-type (mainly α-tocopherol). 2. The formation of secondary carotenoids already starts in the green petals of the buds. Their main synthesis however, proceeds parallel with a partial destruction of chlorophyll and thylakoids. The secondary carotenoids are accumulated predominantly in the plastids of the epidermal and subepidermal cells. Concurrently the number of plastoglobuli is strongly increased. 3. The isolated plastoglobuli show the same size distribution (40–200 nm) as in situ on the electromicrograms. They contain both lipid classes, carotenoids and plastidquinones. Most of the carotenoid-rich Sarothamnus-plastoglobuli are much less electron dense than the plastoglobuli of green leaf tissue, which contain only traces of carotenoids. The general function of plastoglobuli in chromoplasts as stores for carotenoids and plastidquinones is discussed.

CHROMOPLASTS OF TOMATO FRUITS. I. ULTRASTRUCTURE OF LOW‐PIGMENT AND HIGH‐BETA MUTANTS. CAROTENE ANALYSES

Three pigment lines of the tomato cultivar ‘Pearson’ with isogenic backgrounds were studied to determine the relationship between certain carotenoids and the development of chromoplasts during fruit ripening. The lines were normal red (r+/r+), in which about 90% of the carotenoids in the ripe fruit is lycopene; high‐beta (B/B) mutant, in which beta‐carotene is the major pigment and the mature fruit color is deep orange ; and low‐pigment (r/r) mutant, in which carotenoids are drastically reduced and the mature fruit is pale yellow‐orange. This paper reports pigment analyses for the three lines and the ultrastructural changes in plastids of the two mutant lines. Very young, pale green fruits contain proplastids with limited lamellar structure. As the fruits reach the mature green stage, the plastids in all three lines develop into typical chloroplasts. Differences in pigment content and in ultrastructure among the lines are not apparent until ripening commences. In the low‐pigment mutant carotenoids are reduced as ripening progresses and no carotenoid crystalloids are formed. As chlorophyll decreases the fruits become pale yellow. The grana become disorganized and the thylakoids appear to separate at the partitions and tend to be arrayed in lines, some still with their ends overlapping. Globules increase slightly in number. In the high‐beta mutant the grana break down during ripening and globules increase greatly in size and number. Beta‐carotene, presumed to be largely in the globules, crystallizes into elongated or druse type forms which may distort the globules. The crystals may affect the shape of the chromoplasts; long crystals may extend the length of the plastid to over 15 μ. Thylakoid plexes with a regular lattice structure sometimes occur in the chromoplasts of the high‐beta mutant. Granules resembling aggregations of phytoferritin particles occur in the chromoplasts of both of these mutants.

Ultrastructural Development of Chromoplasts in Valencia Oranges

The development of chromoplasts from chloroplasts during ripening of Valencia oranges was followed with the electron microscope. The chloroplasts in the young, green fruit of Valencia were similar in structure to those in leaves of other plants. During ripening, there was a breakdown of the internal membrane system, the grana-fretwork system, and large, osmiophilic globules were formed. These globules apparently formed from breakdown products of the granal membranes as well as from carotenoids synthesized during ripening. During ripening, membranes developed from invagination of the inner part of the limiting membrane of the plastids. These membranes may be associated with chlorophyll that is synthesized during ripening. The breakdown of the grana-fretwork system seemed to be independent and not influenced by the limiting membrane of the plastid.

The submicroscopic development of chromoplasts in the fruit of Capsicum annuum L.

From a structural point of view, there are three different types of chromoplasts in carotinoid pigmented plant organs (8): plastids which contain (1) microscopic crystals of carotinoids, (2) microscopic and submicroscopic yellow globuli, and (3) bundles of orange-red pigmented submicroscopic filaments. After having studied the development of the globuli in the second case (8), an investigation of the transformation of chloroplasts into the spindle-shaped chromoplasts containing submicroscopic filaments (23) has been undertaken. While the ultrastructure of the chloroplast, as well as that of the transformed chromoplast, are fairly stable and can be satisfactorily fixed, the stages of transition appear to be very unstable so that it is difficult to avoid swelling and artifacts even with osmic acid or permanganate. The filaments appear as bundles during and directly after the disintegration of the grana in the chloroplastic structure. But there is no direct transformation of the grana into the bundles of long filaments because only a few (3 or 4) such bundles are formed, while the grana are numerous (Fig. 2). Apart from their shape, the filaments display a similar ultrastructure to the grana discs in the active chloroplast because they show a denser osmophilic rind measuring 50 A in width and a less dense colorless core (Figs. 15 and 16). The origin and development of these filaments, which present some morphological resemblance to filamentous virus particles, is discussed.

Die Submikroskopische Entwicklung der Chromoplasten in den Blüten von Ranunculus Repens L

Electron microscopic studies of the development of yellow chromoplasts in the perianth ofRanunculus repens L. show, that the structures characteristic of these yellow plastids are homogeneous osmophilic globuli up to 1500 A in diameter which first appear in young chloroplasts or leucoplasts. They are formed between the lamellae and, while increasing in size and number, they destroy the lamellar structure until at maturity only these droplets remain lining the inner surface of the plastid membrane. It is most likely that they are formed as a result of lipophanerosis of the lamellar structures and that they represent the final stage in a monotropic plastid metamorphosis and can not revert to chloro-, or leucoplasts. This is supporting evidence for the theory of monotropic plastid transformation. Transition forms have been found, having structures characteristic of both leuco-, chloro-, and chromoplasts at the same time, thus making the usual classification into these categories no longer tenable on the basis of submicroscopic morphology.