Red Chlorophyll Catabolite Reductase Research Articles

RsOBP2a, a member of OBF BINDING PROTEIN transcription factors, inhibits two chlorophyll degradation genes in green radish

The green radish (Raphanus sativus L.) contains abundant chlorophyll (Chl). DOF-type transcription factor OBF BINDING PROTEIN (OBP) plays crucial functions in plant growth, development, maturation and responses to various abiotic stresses. However, the metabolism by which OBP transcription factors regulate light-induced Chl metabolism in green radish is not well understood. In this study, six OBP genes were identified from the radish genome, distributed unevenly across five chromosomes. Among these genes, RsOBP2a showed significantly higher expression in the green flesh compared to the white flesh of green radish. Analysis of promoter elements suggested that RsOBPs might be involved in stress responses, particularly in light-related processes. Overexpression of RsOBP2a led to increase Chl levels in cotyledons and adventitious roots of radish, while silencing RsOBP2a expression through TYMV-induced gene silencing accelerated leaf senescence. Further investigations revealed that RsOBP2a was localized in the nucleus and served as a transcriptional repressor. RsOBP2a was induced by light and directly suppressed the expression of STAYGREEN (SGR) and RED CHLOROPHYLL CATABOLITE REDUCTASE (RCCR), thereby delaying senescence in radish. Overall, a novel regulatory model involving RsOBP2a, RsSGR, and RsRCCR was proposed to govern Chl metabolism in response to light, offering insights for the enhancement of green radish germplasm.

Physiological and transcriptomic strategies related to photosynthesis of rice in response to vanadium stress

Vanadium (V) is recognized as an environmental contaminant that affects plant growth and development. However, the photosynthetic response of plants to V stress at molecular level remains unclear. In this study, we examined the photosynthetic responses of two rice varieties (Oryza sativa L.) with diverse V tolerance under various V levels (0, 10, 20, 30, and 40 mg L−1) using physiological, cytological, and transcriptomic approaches. Our findings indicated that V stress significantly reduced the photosynthetic rate and chlorophyll content in both genotypes, with the V-sensitive rice displaying a more pronounced reduction. Furthermore, we observed numerous plastoglobuli, deformed stroma, and ruptured thylakoid membranes in the chloroplasts of the V-sensitive rice. In transcriptome analysis, we found 34 differentially expressed genes of 21 enzymes potentially affect chlorophyll metabolism. Among them, most of the genes involved in chlorophyll biosynthesis and phototoxic intermediate degradation were down-regulated under V stress, while chlorophyll degradation-related genes exhibited up-regulation. In addition, the different expression levels of genes encoding uroporphyrinogen III synthase (UROS), protoporphyrinogen oxidase (PPO), chlorophyllase (CLH), pheophorbide a oxygenase (PAO), and red chlorophyll catabolite reductase (RCCR) between the two rice varieties may indicate a potential tolerance mechanism in rice plants in response to V stress. Overall, this study contributes to our understanding of the molecular mechanisms underlying plant tolerance to V toxicity, while also highlighting potential targets for improving plant tolerance in V-contaminated soils.

Inhibition of red chlorophyll catabolite reductase improved chlorophyll and carotenoid synthesis in tobacco

Inhibition of red chlorophyll catabolite reductase improved chlorophyll and carotenoid synthesis in tobacco

Unravelling the Role of Piriformospora indica in Combating Water Deficiency by Modulating Physiological Performance and Chlorophyll Metabolism-Related Genes in Cucumis sativus

Water stress is the most critical aspect restricting the development of agriculture in regions with scarce water resources, which requires enhancing irrigation water-saving strategies. The current work discusses the potential application of the plant-strengthening root endophyte Piriformospora indica against moderate (25% less irrigation water) and severe (50% less irrigation water) water stress in comparison to the optimum irrigation conditions of greenhouse cucumbers. P. indica improved growth, nutrient content, and photosynthesis apparatus under normal or water-stress conditions. On the other hand, moderate and severe water stress reduced yield up to 47% and 83%, respectively, in non-colonized cucumber plants, while up to 28 and 78%, respectively, in P. indica-colonized plants. In terms of water-use efficiency (WUE), P. indica improved the WUE of colonized cucumber plants grown under moderate (26 L/kg) or severe stress (73 L/kg) by supporting colonized plants in producing higher yield per unit volume of water consumed by the crop in comparison to non-colonized plants under the same level of moderate (43 L/kg) or severe (81 L/kg) water stress. Furthermore, P. indica increased the indole-3-acetic acid (IAA) content, activity levels of catalase (CAT) and peroxidase (POD) with an apparent clear reduction in the abscisic acid (ABA), ethylene, malondialdehyde (MDA), proline contents and stomatal closure compared to non-stressed plants under both water-stress levels. In addition, chlorophyll a, b, a + b contents were increased in the leaves of the colonized plants under water-stress conditions. This improvement in chlorophyll content could be correlated with a significant increment in the transcripts of chlorophyll biosynthesis genes (protochlorophyllide oxidoreductase [POR], chlorophyll a oxygenase [CAO]) and a reduction in the chlorophyll degradation genes (PPH, pheophorbide a oxygenase [PAO], and red chlorophyll catabolite reductase [RCCR]). In conclusion, P. indica has the potential to enhance the cucumber yield grown under moderate water stress rather than severe water stress by improving WUE and altering the activity levels of antioxidant enzymes and chlorophyll metabolism-related genes.

VvERF17 mediates chlorophyll degradation by transcriptional activation of chlorophyll catabolic genes in grape berry skin

Chlorophylls in the skin contribute to grape (Vitis vinifera) berry color and quality. Degradation of chlorophyll occurs during berry development in grape, but less is known about the molecular mechanisms of this process. Here, we characterized an ethylene response factor, VvERF17, as a putative regulator of chlorophyll degradation in grape berry. VvERF17 expression was strongly correlates with development-induced and ETH-triggered chlorophyll degradation. Transient overexpression of VvERF17 in tobacco leaves, tomato fruits, and grape leaves led to color break and chlorophyll degradation, which were resulted from the upregulated expression of chlorophyll catabolic genes (CCGs), including Chlorophyll-b-reductase (NOL), pheophytinase (PPH), pheophorbide a oxygenase (PAO), and red Chlorophyll catabolite reductase (RCCR). Inversely, silencing of VvERF17 in grape leaves partially suppressed the expression of CCGs’ expression. Major CCGs’ expression was closely related to chlorophyll degradation and VvERF17 expression. It was further demonstrated that VvERF17 could activate the expression of major CCGs by directly binding to the ERF binding sites in their promoters. We conclude that VvERF17 mediates chlorophyll degradation by transcriptional activation of NOL, PPH, PAO, and RCCR. These findings elucidate the regulation mechanisms of chlorophyll degradation in grape and enrich our understanding of grape berry color formation.

High oxygen atmospheric packaging treatment regulates the postharvest changes of Chinese kale (Brassica oleracea var. alboglabra) during storage.

Chinese kale is one of the most popular vegetables in southern China and Asia, but it has a short shelf-life. The effect of high oxygen atmospheric packaging (HOAP) treatment on the respiration rate as well as chlorophyll content and the expression of their metabolism-related genes of the soluble proteins in Chinese kale during storage were assessed. The results showed that Chinese kale subjected to HOAP treatment showed stimulated respiration rate and regulated expression of chlorophyll metabolism-related genes, such as BrChlases, BrPPH (pheophytin pheophorbide hydrolase), BrPAO (pheidea oxygenase gene), BrRCCR (red chlorophyll catabolite reductase), and BrSAG12 (senescence-associated gene), compared to the Chinese kale in the control. The activities of chlorophyll enzymes, that is, Chlase and Mg-dechelatase, were also influenced by HOAP treatment during storage. Furthermore, the total content of soluble proteins was stimulated to accumulate, and the intensity of protein bands, detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiling, increased in HOAP-treated samples. Based on the current results, as well as the results of our previous study regarding HOAP treatment of other vegetables, we speculate that HOAP may function by regulating the respiration rate and the accumulation of functional proteins, especially chlorophyll catabolic and antioxidant enzymes, to maintain the freshness of Chinese kale during storage. PRACTICAL APPLICATION: HOAP treatment could be a potential method for delaying quality changes and extending the shelf-life of Chinese kale after harvest.

Improvement of fruit quality and pedicel color of cold stored sweet cherry in response to pre-storage 1-methylciclopropene and chlorine dioxide treatments: Combination treatment of 1-MCP plus ClO2 improves post-harvest quality of sweet cherry fruit

Sweet cherry fruit is perishable which quality loss greatly influences consumers preference. To improve postharvest quality of sweet cherry, the effect of the combination of 1-methylciclopropene (1-MCP) plus chlorine dioxide (ClO2) was estimated by analyses of postharvest characteristics, bioactive compounds, antioxidant capacity and pedicel quality changing. The fruit was treated separately or in combination with 1-MCP and ClO2, which were stored at 4 °C for 25 d. In comparison with individual treatment, the combination treatment of 1-MCP and ClO2 delayed senescence by suppressing decay incidence, softening and the reduction of ascorbic acid, total phenolic as well as titratable acid. In addition, combination of 1-MCP + ClO2 inhibited the decreasing of pedicel browning and pedicel force, maintained the higher content of chlorophyll more effectively. Moreover, 1-MCP or ClO2 individual treatment remarkably inhibited the expression of genes, including pheophytin pheophorbide hydrolase, chlorophyllase, pheophorbide a oxygenase and red chlorophyll catabolite reductase, associated to chlorophyll catabolism in cherry pedicel. Additionally, compared to the individual treatment, the combination of 1-MCP + ClO2 contributed the maximum efficacy, especially in the middle duration of storage. Overall, our preliminary study suggested that the combined treatment of 1-MCP + ClO2 might be a promising method to preserve postharvest quality in sweet cherry fruit.

Melatonin delays yellowing of broccoli during storage by regulating chlorophyll catabolism and maintaining chloroplast ultrastructure

• Exogenous melatonin markedly extended the shelf life of broccoli. • Melatonin delayed the decline of chlorophyll content and chloroplast breakdown. • Melatonin regulated activities and gene expressions of chlorophyll catabolic enzymes. • Melatonin regulated the expressions of BoSGR1 and BoSGR2 . The effect of melatonin treatment on color, chlorophyll degradation and chloroplast structure in broccoli during storage was evaluated. One hundred μmmol L −1 melatonin markedly extended the shelf life of broccoli. Compared with control florets, melatonin treatment delayed the decline of chlorophyll content, and maintained more intact chloroplasts. Meanwhile, melatonin also suppressed the activities of chlorophyll catabolic enzymes such as chlorophyllase (CLH), pheophytinase (PPH), pheophorbide a oxygenase (PAO) and red chlorophyll catabolite reductase (RCCR), and down-regulated the expressions of BoNYC1 , BoNOL , BoCLH , BoPPH , BoPAO , BoRCCR and BoSGR1 involved in chlorophyll catabolism. Taken together, our results indicated that melatonin could be a good candidate for delaying yellowing in broccoli during storage at 20 ℃.

Enhanced Chlorophyll Degradation Triggers the Pod Degreening of "Golden Hook," a Special Ecotype in Common Bean (Phaseolus vulgaris L.).

To reveal genetic factors or pathways involved in the pod degreening, we performed transcriptome and metabolome analyses using a yellow pod cultivar of the common bean “golden hook” ecotype and its green pod mutants yielded via gamma radiation. Transcriptional profiling showed that expression levels of red chlorophyll catabolite reductase (RCCR, Phvul.008G280300) involved in chlorophyll degradation was strongly enhanced at an early stage (2 cm long) in wild type but not in green pod mutants. The expression levels of genes involved in cellulose synthesis was inhibited by the pod degreening. Metabolomic profiling showed that the content of most flavonoid, flavones, and isoflavonoid was decreased during pod development, but the content of afzelechin, taxifolin, dihydrokaempferol, and cyanidin 3-O-rutinoside was remarkably increased in both wild type and green pod mutant. This study revealed that the pod degreening of the golden hook resulting from chlorophyll degradation could trigger changes in cellulose and flavonoids biosynthesis pathway, offering this cultivar a special color appearance and good flavor.

Synergistic inhibitory effect of 1-methylcyclopropene (1-MCP) and chlorine dioxide (ClO2) treatment on chlorophyll degradation of green pepper fruit during storage

Abstract Degreening indicates the ripening and senescence process of green pepper fruit, which mainly results from chlorophyll degradation. To date, however, the effect of 1-Methylcyclopropene (1-MCP) alone or in combination with chlorine dioxide (ClO2) on the chlorophyll degradation pathway of green pepper at the molecular level remains scarce. In this study, green peppers were treated with 1 μL L−1 1-MCP, 30 μL L−1 ClO2 alone and 1 μL L−1 1-MCP plus 30 μL L−1 ClO2, respectively and stored at 20 °C for 12 d. The results showed that 1-MCP + ClO2 combination was superior in inhibiting color changes, decreasing the respiration rate, and exhibiting chlorophyll content as compared with 1-MCP or ClO2 alone. Further study on the expression of genes related to chlorophyll degradation pathway revealed that pheophytinase (PPH), pheophorbide a oxygenase (PAO) and red chlorophyll catabolite reductase (RCCR) were suppressed by all treatments. The efficiency of the combined treatment (1-MCP + ClO2) was better than that of 1-MCP or ClO2 alone. While the expression of chlorophyllase (CLH) was not affected by ClO2, but was significant suppressed by 1-MCP and 1-MCP + ClO2. Therefore, our results indicate the different regulatory roles of 1-MCP and ClO2 on the chlorophyll degradation pathway and provide an efficient method to preserve green pepper.

Deciphering the Role of Stay-Green Trait to Mitigate Terminal Heat Stress in Bread Wheat

The present study aimed to reveal the impact of the stay-green trait in bread wheat under terminal heat stress. Field experiments (early and late sowing; for two consecutive years) were conducted to investigate the influence of terminal heat stress on the morpho-physiological traits in different stay-green types i.e., non-stay-green, moderately non-stay-green, moderately stay-green, and stay-green. In addition, the greenhouse experiment was performed to dissect the stay-green trait in functional stay-green, non-functional stay-green, and non-stay-green genotypes. The results of the field experiments confirmed that genotypes exhibiting the stay-green trait have a significantly high chlorophyll content, normalized difference vegetative index, grain yield, biological yield, kernel weight, and low canopy temperature under control and heat stress conditions. In the greenhouse experiment, functional stay-green and non-functional stay-green genotypes showed a high chlorophyll content and photochemical efficiency, whereas biological yield and grain yield showed a significant relation with the functional stay-green genotype under control and terminal heat stress treatments. The sequencing and expression analysis of chlorophyllide a oxygenase (CaO), light-harvesting complex (Cab), stay-green (SGR), and red chlorophyll catabolite reductase (RCCR) in functional stay-green, non-functional stay-green, and non-stay-green genotypes revealed variations in the exons of CaO and RCCR; and significant difference in the regulation of CaO and Cab at 7 days after anthesis under terminal heat stress. This study confirms that genotypes displaying the stay-green trait can aid wheat breeders to cope with increasing temperature in the impending decades.

Dark/Light Treatments Followed by γ-Irradiation Increase the Frequency of Leaf-Color Mutants in Cymbidium.

Radiation randomly induces chromosomal mutations in plants. However, it was recently found that the frequency of flower-color mutants could be specifically increased by upregulating anthocyanin pathway gene expression before radiation treatments. The mechanisms of chlorophyll biosynthesis and degradation are active areas of plant study because chlorophyll metabolism is closely connected to photosynthesis. In this study, we determined the dark/light treatment conditions that resulted in upregulation of the expression levels of six chlorophyll pathway genes, uroporphyrinogen III synthase (HEMD), uroporphyrinogen III decarboxylase (HEME2), NADPH-protochlorophyllide oxidoreductase (POR) A (PORA), chlorophyll synthase (CHLG), chlorophyllase (CLH2), and red chlorophyll catabolite reductase (RCCR), and measured their effects on the γ-irradiation-induced frequencies of leaf-color mutants in two Cymbidium cultivars. To degrade chlorophyll in rhizomes, 60–75 days of dark treatment were required. To upregulate the expressions of chlorophyll pathway genes, 10 days of light treatment appeared to be optimal. Dark/light treatments followed by γ-irradiation increased chlorophyll-related leaf mutants by 1.4- to 2.0-fold compared with γ-ray treatment alone. Dark/light treatments combined with γ-irradiation increased the frequency of leaf-color mutants in Cymbidium, which supports the wider implementation of a plant breeding methodology that increases the mutation frequency of a target trait by controlling the expression of target trait-related genes.

BrTCP7 Transcription Factor Is Associated with MeJA-Promoted Leaf Senescence by Activating the Expression of BrOPR3 and BrRCCR.

The plant hormone jasmonic acid (JA) has been recognized as an important promoter of leaf senescence in plants. However, upstream transcription factors (TFs) that control JA biosynthesis during JA-promoted leaf senescence remain unknown. In this study, we report the possible involvement of a TEOSINTE BRANCHED1/CYCLOIDEA/PCF (TCP) TF BrTCP7 in methyl jasmonate (MeJA)-promoted leaf senescence in Chinese flowering cabbage. Exogenous MeJA treatment reduced maximum quantum yield (Fv/Fm) and total chlorophyll content, accompanied by the increased expression of senescence marker and chlorophyll catabolic genes, and accelerated leaf senescence. To further understand the transcriptional regulation of MeJA-promoted leaf senescence, a class I member of TCP TFs BrTCP7 was examined. BrTCP7 is a nuclear protein and possesses trans-activation ability through subcellular localization and transcriptional activity assays. A higher level of BrTCP7 transcript was detected in senescing leaves, and its expression was up-regulated by MeJA. The electrophoretic mobility shift assay and transient expression assay showed that BrTCP7 binds to the promoter regions of a JA biosynthetic gene BrOPR3 encoding OPDA reductase3 (OPR3) and a chlorophyll catabolic gene BrRCCR encoding red chlorophyll catabolite reductase (RCCR), activating their transcriptions. Taken together, these findings reveal that BrTCP7 is associated with MeJA-promoted leaf senescence at least partly by activating JA biosynthesis and chlorophyll catabolism, thus expanding our knowledge of the transcriptional mechanism of JA-mediated leaf senescence.

Chlorine dioxide delays the reddening of postharvest green peppers by affecting the chlorophyll degradation and carotenoid synthesis pathways

The change in colour from green to red, known as reddening, is a major problem in green pepper cultivation, implying ripening and senescence. Chlorine dioxide (ClO2) is used to preserve the quality of vegetables and fruits because of its safety. In this work, the effects of ClO2 on reddening in green peppers, their chlorophyll and carotenoid content, and the molecular mechanisms involved are studied. The results show that 30 μL L−1 of ClO2 treatment reduced the reddening rate markedly compared to the control. ClO2 delayed the degradation of chlorophyll and significantly reduced the synthesis of capsanthin and β-carotene. Additionally, the transcript levels of pheophytin pheophorbide hydrolase (PPH), pheophorbide a oxygenase (PAO), and red chlorophyll catabolite reductase (RCCR) genes, associated with chlorophyll breakdown, were inhibited by ClO2 treatment, and the relative expression of phytoene synthase (Psy), lycopene β-cyclase enzyme (Lcyb), capsanthin/capsorubin synthase (Ccs), and β-carotene hydroxygenase enzyme (Crtz) genes, associated with carotenoid synthesis, were suppressed. These findings indicate that ClO2 delayed reddening by suppressing the expression of certain genes associated with chlorophyll breakdown and carotenoid synthesis in harvested green peppers.

Molecular Mechanisms Preventing Senescence in Response to Prolonged Darkness in a Desiccation-Tolerant Plant.

The desiccation-tolerant plant Haberlea rhodopensis can withstand months of darkness without any visible senescence. Here, we investigated the molecular mechanisms of this adaptation to prolonged (30 d) darkness and subsequent return to light. H. rhodopensis plants remained green and viable throughout the dark treatment. Transcriptomic analysis revealed that darkness regulated several transcription factor (TF) genes. Stress- and autophagy-related TFs such as ERF8, HSFA2b, RD26, TGA1, and WRKY33 were up-regulated, while chloroplast- and flowering-related TFs such as ATH1, COL2, COL4, RL1, and PTAC7 were repressed. PHYTOCHROME INTERACTING FACTOR4, a negative regulator of photomorphogenesis and promoter of senescence, also was down-regulated. In response to darkness, most of the photosynthesis- and photorespiratory-related genes were strongly down-regulated, while genes related to autophagy were up-regulated. This occurred concomitant with the induction of SUCROSE NON-FERMENTING1-RELATED PROTEIN KINASES (SnRK1) signaling pathway genes, which regulate responses to stress-induced starvation and autophagy. Most of the genes associated with chlorophyll catabolism, which are induced by darkness in dark-senescing species, were either unregulated (PHEOPHORBIDE A OXYGENASE, PAO; RED CHLOROPHYLL CATABOLITE REDUCTASE, RCCR) or repressed (STAY GREEN-LIKE, PHEOPHYTINASE, and NON-YELLOW COLORING1). Metabolite profiling revealed increases in the levels of many amino acids in darkness, suggesting increased protein degradation. In darkness, levels of the chloroplastic lipids digalactosyldiacylglycerol, monogalactosyldiacylglycerol, phosphatidylglycerol, and sulfoquinovosyldiacylglycerol decreased, while those of storage triacylglycerols increased, suggesting degradation of chloroplast membrane lipids and their conversion to triacylglycerols for use as energy and carbon sources. Collectively, these data show a coordinated response to darkness, including repression of photosynthetic, photorespiratory, flowering, and chlorophyll catabolic genes, induction of autophagy and SnRK1 pathways, and metabolic reconfigurations that enable survival under prolonged darkness.

The positive roles of exogenous putrescine on chlorophyll metabolism and xanthophyll cycle in salt-stressed cucumber seedlings

The effects of foliar spray of putrescine (Put; 8 mM) on chlorophyll (Chl) metabolism and xanthophyll cycle in cucumber seedlings were investigated under saline conditions of 75 mM NaCl. Exogenous Put promoted the conversion of uroporhyrinogen III to protoporphyrin IX and alleviated decreases in Chl contents and in a size of the xanthophyll cycle pool under salt stress. Moreover, the Put treatment reduced the activities of uroporphyrinogen III synthase, chlorophyllase, and Mg-dechelatase and downregulated the transcriptional levels of glutamyl-tRNA reductase, 5-aminolevulinate dehydratase, uroporphyrinogen III synthase, uroporphyrinogen III decarboxylase, and chlorophyllide a oxygenase, but significantly increased the expression levels of non-yellow coloring 1-like, pheide a oxygenase, red chlorophyll catabolite reductase, and violaxanthin de-epoxidase. Taken together, these results suggest that Put might improve Chl metabolism and xanthophyll cycle by regulating enzyme activities and mRNA transcription levels in a way that improved the salt tolerance of cucumber plants.

Effect of modified atmosphere packaging (MAP) on rachis quality of ‘Red Globe’ table grape variety

Rachis browning corresponds to a postharvest disorder that drastically reduces overall table grape quality. This problem has been associated mainly to water loss, but the possibility of having other factors involved like green pigment degradation and brownish compound synthesis that mask the green tissue is also feasible. Modified Atmosphere Packaging (MAP) is a technology used to extend table grape postharvest life, including rachis appearance. The objective of this study was to analyze the effects caused by MAP on rachis browning during cold storage of ‘Red Globe’ table grape variety. MAP helped to reduce the green color loss on rachises stored for 90days of storage at 0°C compared with a conventional storage (CS) even after a shelf life period, without to affect negatively the quality of the berries. Interestingly, MAP storage decreased the content of chlorophyll-a and increased the amount of pheophytin-a, a chlorophyll degradation product, compared to CS both after cold storage period and shelf life. Additionally, the expression of genes involved in the chlorophyll breakdown pathway was analyzed by qPCR. We found that MAP induced an increase in the transcript abundance of metal-chelating substance (MCS) and Red Chlorophyll Catabolite Reductase (RCCR) genes. However, Pheophytinase (PPH) and Pheophorbide-a Oxigenase (PaO) transcript accumulation revealed no changes compared with CS. Apparently, MAP generated a modification in the chlorophyll breakdown process allowing an accumulation of green like compounds responsible for the greener color of rachises in the MAP stored bunches. On the other hand, histological analysis reveals that after cold storage and shelf life, morphological changes and brown compounds accumulation take place at the periderm and cortex tissues, and these symptoms are less severe in MAP stored bunches helping to keep longer the green coloration of the rachises. In this study we observed that MAP storage increases rachis postharvest quality by reducing green color loss probably due to a combination of processes involving a delay of green pigments degradation and a less accumulation of brown compounds at the periderm and cortex tissues, thus preventing green pigments masking.

Cloning and expression analysis of pepper chlorophyll catabolite reductase gene CaRCCR.

Opening the porphyrin macrocycle of pheophorbide a and forming the primary fluorescent chlorophyll catabolites are key steps in the chlorophyll catabolism pathway. These steps are catalyzed by pheophorbide a oxygenase and red chlorophyll catabolite reductase (RCCR). In this study, a novel RCCR gene, CaRCCR, was isolated from the pepper (Capsicum annuum L.). The full-length CaRCCR complementary DNA is comprised of 1173 bp, contains an open reading frame of 945 bp, and encodes a 314-amino acid protein. This deduced protein belongs to the ferredoxin-dependent bilin reductase family. Amino acid sequence alignment showed that CaRCCR shared a high homology to other higher plant RCCR proteins. CaRCCR expression, as determined by quantitative real-time polymerase chain reaction, was higher in the leaves than the roots, stems, flowers, and immature fruits. CaRCCR expression was almost constant during all phases of leaf development. It was upregulated by abscisic acid, methyl jasmonate, and salicylic acid. Moreover, CaRCCR was induced by high salinity and drought stress treatments; it was also slightly regulated by Phytophthora capsici. Taken together, these results suggest that CaRCCR is involved in defense responses to various stresses.

Study of interaction between Papaya ringspot virus HC-Pro and papaya (Carica papaya) proteins

Helper component proteinases (HC-Pro) are multifunctional potyvirus proteins involved in transmission of polyproteins by aphids. HC-Pro functions include suppression of antiviral RNA silencing and interfering with host symptom expression. Affinity purification-mass spectrometry was used in the present study of in vitro interactions between a recombinant Papaya ringspot virus HC-Pro protein and 23 papaya proteins extracted from the leaves of healthy and virus-infected papaya and identified by liquid chromatography–tandem mass spectrometry. Ten of the identified proteins were found to be involved in plant defense mechanisms (lipoxygenase and TIR-NBS disease resistance-like protein), photosynthesis (bisphosphate carboxylase large chain and red chlorophyll catabolite reductase), transcription (reverse transcriptase), translation (chromosome associate protein subunit h), signal transduction (membrane protein and calcium-dependent lipid-binding-like protein) and carbohydrate metabolism (sucrose-UDP glucosyltransferase and β-1,4-mannosyltransferase). In addition, the interactions between Papaya ringspot virus HC-Pro protein and host proteins may not only provide a better understanding of how viruses replicate and cause disease, but also help elucidate the molecular mechanisms underlying its various functions.

Effects of 1-MCP on chlorophyll degradation pathway-associated genes expression and chloroplast ultrastructure during the peel yellowing of Chinese pear fruits in storage

The peel yellowing is an important pigment physiological process of green fruit ripening, which mainly results from chlorophyll degradation in the fruit peel. In this work, two typical cultivars with different ripening speed, a slow ripening pear ‘Emerald’ (Pyrus bretschneideri Rehd. cv. Emerald) and a fast ripening ‘Jingbai’ (Pyrus ussuriensis Maxim. cv. Jingbai) were used to investigate the molecular mechanism of chlorophyll degradation in pear yellowing/ripening during postharvest storage. The fruits after harvest were treated with 1-methylcyclopropene (1-MCP), an ethylene action inhibitor at 1.0μLl−1 to determine its effect on chloroplast ultrastructure and the expression of chlorophyll degradation associated genes in peel tissues. Our results show that the pears treated with 1-MCP had a lower ethylene production rate and higher chlorophyll content compared to those of untreated fruit. The more intact chloroplasts with well-organised grana thylakoids and small plastoglobuli were maintained in the peel of 1-MCP treated fruit for up to 30 and 15d in ‘Emerald’ and ‘Jingbai’, respectively. The expression of chlorophyll degradation associated genes: pheophorbide a oxygenase (PAO), non-yellow colouring (NYC), NYC1-like (NOL), stay-green 1(SGR1), was suppressed, while no significant change was found in chlorophyllase 1 (CHL1) and red chlorophyll catabolite reductase (RCCR) in both cultivar fruits treated with 1-MCP. These results suggest that 1-MCP can delay chlorophyll degradation by inhibiting ethylene production and suppressing the gene expression of PAO, NYC, NOL and SGR1, which are closely associated with chlorophyll catabolic pathway.