Search Results (45)

Leaf senescence is a major concern for postharvest leafy vegetables, as leaves are highly prone to yellowing and nutrient loss, resulting in reduced commercial value and limited shelf-life. This study aimed to investigate the effect of L-cysteine (L-cys) on postharvest Chinese flowering cabbage stored at 20 °C. The results showed that 0.5 g L⁻¹ L-cys treatment effectively slowed leaf senescence by downregulating chlorophyll degradation genes (BrNYC1, BrNOL, BrPPH, BrPAO, BrNYE, and BrSAGs) and senescence marker gene BrSAG12. Moreover, this treatment exhibited positive influence on the nutritional quality of cabbage. Also, L-cys treatment maintained ROS homeostasis, preventing excessive ROS accumulation and lipid membrane oxidation. L-cys treatment also maintained a higher total antioxidant capacity and scavenging rate of •OH and O₂^•−. Additionally, L-cys treatment maintained high levels of ascorbate and glutathione and activated antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) and the expression of the encoding genes. Furthermore, L-cys treatment elevated endogenous H₂S levels, which are correlated with increased L-cysteine desulfhydrase activity and the upregulation of H₂S biosynthesis-related genes. These findings suggest that L-cys can delay leaf senescence by reducing chlorophyll breakdown, maintaining ROS homeostasis, and stimulating endogenous H₂S production. Full article

Torreya grandis is a widely cultivated fruit species in China that is valued for its significant economic and agricultural importance. The molecular mechanisms underlying pigment formation and photosynthetic performance in Torreya leaf color mutants remain to be fully elucidated. In this study, we performed transcriptome sequencing and measured photosynthetic performance indicators to compare mutant and normal green leaves. The research results indicate that the identified Torreya mutant differs from previously reported mutants, exhibiting a weakened photoprotection mechanism and a significant reduction in carotenoid content of approximately 33%. Photosynthetic indicators, including the potential maximum photosynthetic capacity (F_v/F_m) and electron transport efficiency (Ψ_o, φ_Eo), decreased significantly by 32%, 52%, and 49%, respectively. While the quantum yield for energy dissipation (φ_Do) increased by 31%, this increase was not statistically significant, which may further reduce PSII activity. A transcriptome analysis revealed that the up-regulation of chlorophyll degradation-related genes—HCAR and NOL—accelerates chlorophyll breakdown in the Torreya mutant. The down-regulation of carotenoid biosynthesis genes, such as LCY1 and ZEP, is strongly associated with compromised photoprotective mechanisms and the reduced stability of Photosystem II. Additionally, the reduced expression of the photoprotective gene psbS weakened the mutant’s tolerance to photoinhibition, increasing its susceptibility to photodamage. These changes in gene expression accelerate chlorophyll degradation and reduce carotenoid synthesis, which may be the primary cause of the yellowing in Torreya. Meanwhile, the weakening of photoprotective mechanisms further impairs photosynthetic efficiency, limiting the growth and adaptability of the mutants. This study emphasizes the crucial roles of photosynthetic pigments and photosystem structures in regulating the yellowing phenotype and the environmental adaptability of Torreya. It also provides important insights into the genetic regulation of leaf color in relation to photosynthesis and breeding. Full article

Kiwifruit cultivars include fruit having a diversity of flesh colors in the range red to yellow to green, associated with specific pigment accumulations. In the yellow-fleshed cultivars, chlorophyll degradation is necessary to unmask the underlying carotenoid pigments, which are responsible for the yellow color. This study aimed to confirm the enzyme activity involved in chlorophyll degradation using different degreening temperatures in the yellow-fleshed kiwifruit (cv. ‘Kiss’, Actinidia chinensis var. chinensis) and in the contrasting green-fleshed kiwifruit (cv. ‘Hayward’, Actinidia chinensis var. deliciosa). Cultivar ‘Kiss’ was harvested at hue angle 106.9° and degreening was carried out at 0, 5, 10 or 15 °C for 41 d. Additionally, one week later, a second batch of the same cultivar was subsequently treated at 30 °C for one week to explore the inhibitory effect on degreening and to elucidate the roles of chlorophyllase and magnesium dechelatase enzymes in the process. Fruit degreened at 30 °C was maintained at 15 °C for 23 d afterward and was compared with fruit stored at 0 °C or at 15 °C for 30 d. Similar degreening treatments were applied to cv. ‘Hayward’ at commercial maturity. Every seven days, flesh color, pigment concentrations and the activities of chlorophyllase and magnesium dechelatase in the flesh were evaluated. Degreening of ‘Kiss’ kiwifruit was enhanced by 15 °C treatment or by 30 °C treatment for seven days and was associated with increasing carotenoids and decreasing chlorophyll a. The magnesium dechelatase activity was greater in fruit degreening at 15 °C, which was consistently maintained throughout the degreening period; however, the activity remained low at very high temperature (30 °C). Regardless of the above, degreening at 30 °C was not inhibited, showing faster color change and high chlorophyllase activity during the exposure time. In contrast, ‘Hayward’ maintained its green color with high concentrations of chlorophylls and carotenoids. However, the high chlorophyllase and the low magnesium dechelatase activities found in ‘Hayward’, suggest that chlorophyllase enzymes are not the only ones involved in flesh degreening. Full article

The diatom Phaeodactylum tricornutum shows potential as a source for biofuel production because of its considerable lipid content. Fatty acid β-oxidation plays a critical role in lipid breakdown. However, we still have a limited understanding of the role of fatty acid β-oxidation in lipid content in this microalga. In our study, we utilized a CRISPR interference method to reduce the expression of enoyl-CoA hydratase (PtECH), which is involved in the hydration of trans-2-enoyl-CoA to produce 3-hydroxyacyl-CoA during the β-oxidation pathway. Using this method, we developed two transgenic lines, PtECH21 and PtECH1487, which resulted from interference at two different sites of the PtECH gene, respectively. RT-qPCR analysis confirmed that the mRNA levels of PtECH in both mutants were significantly lower compared to the wild type. Surprisingly, the lipid content of both mutants increased notably. Additionally, both knockdown mutants exhibited higher chlorophyll content and improved photosynthetic efficiency of the photosystem II compared to the wild type. This study introduces a new approach for enhancing lipid content in P. tricornutum and expands our knowledge of the functions of enoyl-CoA hydratase in microalgae. Full article

Salt stress significantly reduces rice yield and quality and is a global challenge, especially in arid and semi-arid regions with limited freshwater resources. The present study was therefore conducted to examine the potential of silica nanoparticles (SiO₂ NPs) in mitigating the adverse effects of saline irrigation water in salt-tolerant rice. Two salt-tolerant rice varieties, i.e., Y liangyou 957 (YLY957) and Jingliangyou 534 (JLY534), were irrigated with 0.6% salt solution to simulate high-salt stress and two SiO₂ NPs were applied, i.e., control (CK) and SiO₂ NPs (15 kg hm⁻²). The results demonstrated that the application of SiO₂ NPs increased, by 33.3% and 23.3%, the yield of YLY957 and JLY534, respectively, compared with CK, which was primarily attributed to an increase in the number of grains per panicle and the grain-filling rate. Furthermore, the application of SiO₂ NPs resulted in a notable enhancement in the chlorophyll content, leaf area index, and dry matter accumulation, accompanied by a pronounced stimulation of root system growth and development. Additionally, the SiO₂ NPs also improved the antioxidant enzyme activities, i.e., superoxide dismutase, peroxidase, and catalase activity and reduced the malondialdehyde content. The SiO₂ NPs treatment effectively improved the processing quality, appearance quality, and taste quality of the rice. Furthermore, the SiO₂ NPs resulted in improvements to the rapid viscosity analyzer (RVA) pasting profile, including an increase in peak viscosity and breakdown values and a reduction in setback viscosity. The application of SiO₂ NPs also resulted in a reduction in crystallinity and pasting temperature owing to a reduction in the proportion of B2 + B3 amylopectin chains. Overall, the application of silica nanoparticles improved the quality of rice yield under high-salt stress. Full article

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. Full article

NAC transcription factors are commonly involved in the plant response to drought stress. A transcriptome analysis of root samples of the soybean variety ‘Jiyu47’ under drought stress revealed the evidently up-regulated expression of GmNAC19, consistent with the expression pattern revealed by quantitative real-time PCR analysis. The overexpression of GmNAC19 enhanced drought tolerance in Saccharomyces cerevisiae INVSc1. The seed germination percentage and root growth of transgenic Arabidopsis thaliana were improved in comparison with those of the wild type, while the transgenic soybean composite line showed improved chlorophyll content. The altered contents of physiological and biochemical indices (i.e., soluble protein, soluble sugar, proline, and malondialdehyde) related to drought stress and the activities of three antioxidant enzymes (i.e., superoxide dismutase, peroxidase, and catalase) revealed enhanced drought tolerance in both transgenic Arabidopsis and soybean. The expressions of three genes (i.e., P5CS, OAT, and P5CR) involved in proline synthesis were decreased in the transgenic soybean hairy roots, while the expression of ProDH involved in the breakdown of proline was increased. This study revealed the molecular mechanisms underlying drought tolerance enhanced by GmNAC19 via regulation of the contents of soluble protein and soluble sugar and the activities of antioxidant enzymes, providing a candidate gene for the molecular breeding of drought-tolerant crop plants. Full article

Plants face various biotic and abiotic stress factors during their growth and development, among which, drought is a serious adverse factor that affects yield and quality in agriculture and forestry. Several transcription factors are involved in regulating plant responses to drought stress. In this study, the B-box (BBX) transcription factor CoBBX24 was cloned from Camellia oleifera. This gene encodes a 241-amino-acid polypeptide containing two B-box domains at the N-terminus. A phylogenetic analysis revealed that CoBBX24 and CsBBX24 from Camellia sinensis are in the same branch, with their amino acid sequences being identical by 96.96%. CoBBX24 was localized to the nucleus and acted as a transcriptional activator. The overexpression of CoBBX24 in Arabidopsis heightened its drought tolerance along with a relatively high survival rate, and the rate of water loss in the OX-CoBBX24 lines was observably lower than that of the wild-type. Compared to the wild-type, the root lengths of the OX-CoBBX24 lines were significantly inhibited with abscisic acid. Leaf senescence was delayed in the OX-CoBBX24 lines treated with abscisic acid. The expression of genes related to leaf senescence and chlorophyll breakdown (e.g., SAG12, SAG29, NYC1, NYE1, and NYE2) was downregulated in the OX-CoBBX24 lines. This study indicated that CoBBX24 positively regulates the drought tolerance in Arabidopsis through delayed leaf senescence. Full article

The plant growth regulator ethylene influences rachis browning in grape (Vitis vinifera L.). Although the ethylene signaling pathway is well defined, there is limited knowledge on its mode of action during rachis browning. Here, we show that an ethylene response factor (VvERF111) positively regulates chlorophyll degradation in rachis by binding to a DRE motif in the promoter of VvCLH1. The expression of VvERF111 and VvCLH1 in rachis was induced by ethylene and inhibited by 1-methylcyclopropene (1-MCP). VvERF111 belongs to the ERF IX subfamily of the APETALA2/ethylene responsive factor (AP2/ERF) superfamily, shows transcriptional activity in yeast, and is localized in the nucleus and membrane. The transient overexpression of VvERF111 or chlorophyllase (VvCLH1) in grape leaves accelerated chlorophyll degradation. In VvERF111-overexpressing leaves, transcript levels of VvCLH1 were also increased. Our findings offer a deeper understanding of the transcriptional regulation of chlorophyll degradation during the rachis browning of grape. Full article

Microalgae, eukaryotic unicellular plants that are distributed worldwide, have been shown to exert anti-proliferative and anticancer activities on various human cancer cell lines. An example of a microalgal bioactive compound is a chlorophyll breakdown product named Pheophorbide a (Ppa), which has been reported to have anti-proliferative properties against various cell lines. This compound has also been tested with light exposure in photodynamic therapy for cancer treatment. In this paper, we screened eleven marine microalgae against a panel of cancer cells, and evaluated the synergistic anti-proliferative effect with Pheophorbide a, with and without photo-activation. The results showed significant anti-proliferative activity against melanoma cells when Ppa was combined with fraction E of the diatom Cylindrotheca closterium plus 1 h photo-activation. Its activity was also analyzed using gene expression and Western blot experiments. Altogether, these data give new insights into the possible application of microalgae for photodynamic therapy. Full article

Cut leaves of Davallia solida are widely used in bouquet greenery. However, the leaves wilt and yellow after seven days. Postharvest applications of exogenous cytokinins (CKs), a plant growth regulator (PGR), preventing senescence in many green leafy plants, were studied by pulsing cut D. solida leaves with 6-benzylamiopurine (BA) at a concentration of 100 ppm, or thidiazuron (TDZ) at a concentration of 10 μM for 24 h, compared with distilled water as a control, and then placing the ferns in a controlled room (21 + 2 °C, 70–80% relative humidity (RH), under cool-white fluorescent lights for 12 h/d). Pulsing with BA and TDZ delayed leaf yellowing while preserving chlorophyll (Chl) content. This was due to reduced Chl-degrading enzyme activities on day 8 of the vase life of the leaves, resulting in longer display life of 11.1 and 11.5 days, respectively. TDZ delayed Chl breakdown on day 8 of the vase life of leaves more than was the case for BA. Subsequently, leaves were pulsed in 10 μM TDZ, or distilled water for 24 h, and then 10 leaves from each treatment were packaged in a 25 × 30 cm, 25-μm thickness BOPP bag. All the packages were stored at 10 °C in 10 h/d light for one, two and three weeks, then unpacked and placed in distilled water. Pulsing with TDZ before one-week storage delayed leaf yellowing, maintained Chl content and extended their vase life to 9.6 days compared with one-, two-, and three-week control leaves, which had a vase life of 6.2, 5.8, and 3.6 days, respectively. After one week, the relative fresh weight of the leaves and water uptake did not alter between the control and TDZ groups. The activities of Chl degradation enzymes in the leaves of D. solida pulsed with TDZ prior to storage were significantly suppressed, related to higher Chl content and a lower percentage of leaf yellowing than the control, resulting in a longer vase life of 9.0 days, while the control lasted 7.0 days. A 10 µM TDZ pulsing treatment significantly prevented the yellowing of D. solida fronds during the vase period or storage period, and one-week storage under MA with light conditions is recommended for retaining postharvest quality after storage. Full article

This study explored the role of exogenous α-Toc (0.5 mM) and Asc (1 mM) in alleviating the damaging effects of salt stress in rapeseed plants (Brassica campestris cv. BARI Sarisha-17). Exposure of 21-day-old plants to different levels of salt stress (75 mM and 150 mM NaCl) resulted in the higher accumulation of sodium ions (Na⁺), reduced potassium ion (K⁺) levels, lower K⁺/Na⁺ ratio, increased oxidative damage, chlorophyll (Chl) breakdown, and disrupted antioxidant and glyoxalase systems. Phenotype responses to salt stress included reductions in plant height, shoot fresh weight, dry weight, number of siliques plant⁻¹, silique length, number of seeds silique⁻¹, 1000-seed weight, and seed yield plant⁻¹. Exogenous α-Toc and Asc applications enhanced the levels of endogenous ascorbate, glutathione (GSH), AsA/dehydroascorbate ratios, GSH/glutathione disulfide, ascorbate peroxidase, monodehydroascorbate reductase, glutathione reductase, glutathione peroxidase, and catalase activities in the salt-stressed plants. Exogenous α-Toc and Asc enhanced antioxidant defense system components and insured better oxidative stress tolerance, as indicated by reduced hydrogen peroxide generation, membrane lipid peroxidation, and electrolyte leakage. Exogenous α-Toc and Asc increased glyoxalase I and glyoxalase II activities in the salt-affected plants. Moreover, they regulated proline levels and increased the leaf relative water content, as well as the Chl level. Exogenous α-Toc and Asc also restored growth and improved yield attributes and seed yield per plants in the salt-affected rapeseed. Full article

Phyllobilins are natural products derived from the degradation of chlorophyll, which proceeds via a common and strictly controlled pathway in higher plants. The resulting tetrapyrrolic catabolites—the phyllobilins—are ubiquitous in nature; despite their high abundance, there is still a lack of knowledge about their physiological properties. Phyllobilins are part of human nutrition and were shown to be potent antioxidants accounting with interesting physiological properties. Three different naturally occurring types of phyllobilins—a phylloleucobilin, a dioxobilin-type phylloleucobilin and a phylloxanthobilin (PxB)—were compared regarding potential antioxidative properties in a cell-free and in a cell-based antioxidant activity test system, demonstrating the strongest effect for the PxB. Moreover, the PxB was investigated for its capacity to interfere with immunoregulatory metabolic pathways of tryptophan breakdown in human blood peripheral mononuclear cells. A dose-dependent inhibition of tryptophan catabolism to kynurenine was observed, suggesting a suppressive effect on pathways of cellular immune activation. Although the exact mechanisms of immunomodulatory effects are yet unknown, these prominent bioactivities point towards health-relevant effects, which warrant further mechanistic investigations and the assessment of the in vivo extrapolatability of results. Thus, phyllobilins are a still surprisingly unexplored family of natural products that merit further investigation. Full article

Recent studies have confirmed that chlorophyllase (CLH), a long-found chlorophyll (Chl) dephytylation enzyme for initiating Chl catabolism, has no function in leaf senescence-related Chl breakdown. Yet, CLH is considered to be involved in fruit degreening and responds to external and hormonal stimuli. The purpose of this work was to elucidate in detail the biochemical, structural properties, and gene expression of four CLHs from the Solanum lycopersicum genome so as to understand the roles of Solanum lycopersicum chlorophyllases (SlCLHs). SlCLH1/4 were the predominantly expressed CLH genes during leaf and fruit development/ripening stages, and SlCLH1 in mature green fruit was modulated by light. SlCLH1/2/3/4 contained a highly conserved GHSXG lipase motif and a Ser-Asp-His catalytic triad. We identified Ser159, Asp226, and His258 as the essential catalytic triad by site-directed mutagenesis in recombinant SlCLH1. Kinetic analysis of the recombinant enzymes revealed that SlCLH1 had high hydrolysis activities against Chl a, Chl b, and pheophytin a (Phein a), but preferred Chl a and Chl b over Phein a; SlCLH2/3 only showed very low activity to Chl a and Chl b, while SlCLH4 showed no Chl dephytylation activity. The recombinant SlCLH1/2/3 had different pH stability and temperature optimum. Removal of the predicted N-terminal processing peptide caused a partial loss of activity in recombinant SlCLH1/2 but did not compromise SlCLH3 activity. These different characteristics among SlCLHs imply that they may have different physiological functions in tomato. Full article

In Southeast Asian nations, cultured hybrid groupers are facing serious infestation by the marine parasitic leech Zeylanicobdella arugamensis (Annelida, Hirudinea). They attach to the hybrid groupers by sucking and biting on the surface of the skin, paving the way for secondary infection upon the fish. The objective of the study is to utilize the locally available seaweed to control the infestation of parasitic leeches. The methanol extracts of the brown alga Sargassum polycystum C. Agardh, 1824 (Phaeophyceae) from Sabah were prepared and investigated for antiparasitic efficacy against Z. arugamensis through in vitro bioassay. A total of 126 adult leeches from the host hybrid groupers were obtained from the fish hatchery. The parasitic leeches were treated with the methanol extracts of S. polycystum for 180 min by preparing five different dosages at concentrations of 100, 50, 25, 12.5, and 6.25 mg/mL. The brown alga was found to have high antiparasitic efficacy, resulting in 100% leech mortality over a short period of time. It showed the highest antiparasitic efficacy (total mortality of leeches) in a short time limit of 0.96 ± 0.44 min, for 100 mg/mL of the extract. Observations on leech behavior in the positive control and the seaweed extract treatments showed vigorous swimming before mortality. LC-MS/MS analysis was used to reveal the phytochemical composition of the extract to understand the nature of the main components responsible for its antiparasitic activities. A total of 29 metabolites were identified via Q Exactive HF Orbitrap mass spectrometry, including two flavonoids (ephedrannin A and hinokiflavone), two organoarsenics (1-dimethylarsinoyl-heptadecane and cacodylic acid), four heterocyclic compounds, and two chlorophyll breakdown products. The presence of bioactive compounds could increase the mortality rate of parasitic leeches. Thus, this study concludes that the brown alga showed high efficacy in its antiparasitic activities and can be effectively applied for treatment in grouper aquaculture farms for sustainable aquaculture. Full article