Mechanism Of Chlorophyll Degradation Research Articles

MdSGR2 Negatively Regulates Chlorophyll Degradation in Apple

The color of an apple is an important index of its appearance quality, which affects the fruit’s marketability and value. The green variety “Granny Smith” remains green when ripe, and the pigment in the peel is mainly chlorophyll. The chlorophyll in the peel of the yellow variety “Golden Delicious” degrades as the fruit ripens. To explore the different mechanisms of chlorophyll degradation in the “Golden Delicious” and “Granny Smith” varieties, transcriptomic analysis was performed on the mature peels of both cultivars. High-quality sequences totaling 48,206,940 and 48,796,646 raw bases, as well as 9632 differentially expressed genes (DEGs), were identified. A total of 1206 DEGs were classified in 118 KEGG metabolic pathways. Additionally, 3258 transcription factors from 428 gene families were predicted, and DEGs associated with chlorophyll degradation, including MdSGR2, MdNYC1 and MdHCAR, were identified. Subsequently, the MdSGR2 gene was isolated from the mature peel of “Granny Smith” apples. Subsequent subcellular localization analysis confirmed that MdSGR2 specifically targets chloroplasts. The transient overexpression of MdSGR2 was found to negatively regulate chlorophyll degradation, leading to the inhibition or deceleration of chlorophyll breakdown, thereby maintaining green coloration in the leaves and peel. Conversely, silencing MdSGR2 positively regulated chlorophyll degradation, resulting in chlorosis in the leaves and peel. These findings offer valuable insights into the regulatory mechanism governing apple fruit coloration and lays a solid foundation for further investigation in this field.

BrJUB1, a NAC family transcription factor, regulates postharvest leaf senescence of Chinese flowering cabbage through the transcriptional activation of BrCCGs

ABSTRACT Leaf yellowing caused by chlorophyll degradation directly reduces the commercial quality of post-harvest Chinese flowering cabbage. However, the mechanism of chlorophyll degradation in post-harvest Chinese flowering cabbage remains unclear. In this work, we identified a leaf senescence-responsive NAC family transcription factor, a homologue of JUB1 in Arabidopsis, termed BrJUB1 in post-harvest Chinese flowering cabbage. The expression of BrJUB1 was found to increase continuously during storage time, accompanied by an upregulation of chlorophyll catabolic genes (CCGs) and reduced chlorophyll content. Subcellular localisation and transactivation analyses in tobacco revealed that BrJUB1 possessed two characteristics of transcription factors: nuclear localisation and transactivation of gene activity. More importantly, electrophoretic mobility shift assay and dual-luciferase analysis demonstrated that BrJUB1 bound to NAC recognition sequence in the promoters of major CCGs including BrNYC1, BrPAO, BrPPH1 and BrSGR1, and activated their transcription. Taken together, these findings show that BrJUB1 might act as an important regulator in leaf senescence of post-harvest Chinese flowering cabbage through activating chlorophyll degradation. This study expands our understanding of molecular mechanisms involved in leaf senescence of harvested Chinese cabbage and possibly other leafy vegetables.

Impact of electron beam irradiation on the chlorophyll degradation and antioxidant capacity of mango fruit

At the present, the mechanism of chlorophyll degradation in response to ionizing irradiation in harvested fruits have not been examined. To understand the effect of electron beam (E-beam) irradiation on the chlorophyll degrading pathway in relation to chlorophyll degrading enzymes activity, reactive oxygen species (ROS) and antioxidant capacities of harvested mangoes stored at 13 °C for 16 days were studied. E-beam-treated fruit significantly suppressed the activities of chlorophyll degrading enzymes especially pheophytinase (PPH) and chlorophyll degrading peroxidase (Chl-POX) in the late stage of storage. This resulted in the chlorophyll content being maintained. However, E-beam irradiation did not affect the activities of chlorophyllase (Chlase) and magnesium de-chelatase (MD). The respiration rate, ethylene production, ROS accumulation (hydrogen peroxide [H2O2] and superoxide radical [O−.2]) immediately increased after E-beam treatment, following which they significantly decreased in comparison to the control. E-beam treatment enhanced the fruit’s antioxidant capacity by activating the activities of catalase (CAT) and ascorbate peroxidase (APX) and glutathione (GSH) content, and inactivated the activity of superoxide dismutase (SOD). Further, it did not affect the activity of glutathione reductase (GR) and glutathione disulfide (GSSG), vitamin C content, or total phenolic content. These results imply that E-beam treatment has the potential to delay chlorophyll degradation by suppressing the Chl-POX and PPH activities as well as reduce ROS production via CAT, APX, and SOD activities and GSH content.

Leaf Color and Growth Change of Sedum rubrotinctum Caused by Two Commercial Chemical Products

Sedum rubrotinctum is widely grown as an ornamental because of its attractive leaf shape and color. Increasing the morphological diversity and color will greatly add to its ornamental value. Environmental conditions such as light and temperature can change the leaf color of succulent plants, but the mechanism is uncertain. To examine this mechanism, we tested the effects of two commercial chemical products Sowing Goodliness (Sg) and Aromatic Garden (Ag) on the morphology, pigment content, and growth performance of Sedum rubrotinctum seedlings. The Sg treatment did not change foliage color, but can accelerate plant growth and increase lateral bud number. The Ag treatment had marked changes on the relative proportions of pigments and leaf color, and plant growth was severely reduced with mortality observed in some plants. After Ag stress was discontinued, the surviving plants began to regrow and had good ornamental value but had the fewest number of lateral buds and leaves, and the smallest leaf length and thickness, canopy diameter, and plant height. Foliage color changes are caused directly by shifts in the relative proportions of pigments, particularly chlorophyll b and anthocyanin. In Ag-treated plants, chlorophyll b declined much faster than chlorophyll a, indicating that the transformation of chlorophyll b into chlorophyll a is an important step in the chlorophyll degradation pathway. Ag provides a way to learn more about the mechanism of chlorophyll degradation and should be investigated further. Ag enhanced anthocyanin production rapidly and improved the ornamental value of Sedum rubrotinctum. Different concentrations of Ag and Sg were not studied in this trial and might be tested to determine the ideal balance between leaf color and plant growth.

Genetic and Hormonal Regulation of Chlorophyll Degradation during Maturation of Seeds with Green Embryos.

The embryos of some angiosperms (usually referred to as chloroembryos) contain chlorophylls during the whole period of embryogenesis. Developing embryos have photochemically active chloroplasts and are able to produce assimilates, further converted in reserve biopolymers, whereas at the late steps of embryogenesis, seeds undergo dehydration, degradation of chlorophylls, transformation of chloroplast in storage plastids, and enter the dormancy period. However, in some seeds, the process of chlorophyll degradation remains incomplete. These residual chlorophylls compromise the quality of seed material in terms of viability, nutritional value, and shelf life, and represent a serious challenge for breeders and farmers. The mechanisms of chlorophyll degradation during seed maturation are still not completely understood, and only during the recent decades the main pathways and corresponding enzymes could be characterized. Among the identified players, the enzymes of pheophorbide a oxygenase pathway and the proteins encoded by STAY GREEN (SGR) genes are the principle ones. On the biochemical level, abscisic acid (ABA) is the main regulator of seed chlorophyll degradation, mediating activity of corresponding catabolic enzymes on the transcriptional level. In general, a deep insight in the mechanisms of chlorophyll degradation is required to develop the approaches for production of chlorophyll-free high quality seeds.

CPPB-aE is discovered from photosynthetic benthic dinoflagellates.

Although chlorophyll degradation pathways in higher plants have been well studied, little is known about the mechanisms of chlorophyll degradation in microalgae. In this article, we report the occurrence of a chlorophyll a derivative that has never been discovered in photosynthetic organisms. This chlorophyll derivative emits no fluorescence and has a peculiar absorbance peak at 425, 451, 625, and 685nm. From these features, it was identified as 13(2) ,17(3) -cyclopheophorbide a enol (cPPB-aE), reported as a degradation product of chlorophyll a derived from prey algal cells in heterotrophic protists. We discovered cPPB-aE in six benthic photosynthetic dinoflagellates that are phylogenetically separated into four clades based on SSU rDNA molecular phylogeny. This is the first report of this chlorophyll derivative in photosynthetic organisms and we suggest that the derivative is used to quench excess light energy.

The Mechanism of Chlorophyll Degradation in Plants

The Mechanism of Chlorophyll Degradation in Plants

Mechanism of Chlorophyll Degradation in Harvested Fruits and Vegetables

Mechanism of Chlorophyll Degradation in Harvested Fruits and Vegetables

パセリーにおけるペルオキシダーゼによるクロロフィルの分解

The mechanism of chlorophyll degradation by peroxidase in parsley leaves was studied. Chlorophylls present in the ethyl alcohol (EtOH) extract of parsley leaves were degraded by a peroxidase-hydrogen peroxide system. Purified chlorophylls, however, were not affected by the system, suggesting the existence of a substance which acts together with peroxidase to degrade chlorophyll in parsley leaves.The substance was isolated from the EtOH extract by the methods of solvent fractionation and column chromatography. After hydrolysis, it was identified as an apigenin, which is a major flavonoid contained in parsley, by measuring Rf value on thin layer chromatogram and spectral characteristics.From the results obtained, it is concluded that in parsley leaves chlorophylls are not degraded by peroxidase directly, but that peroxidase oxidizes the apigenin and then the oxidized apigenin degrades chlorophylls.