Pigment Accumulation Research Articles

Adaptive reactions of corn plants to acute ultraviolet radiation

Aim. The goal of this work was to study the adaptive reaction of young corn plants (Zea mays L.) to the action of acute ultraviolet B (UV-B) radiation in the vegetative growth period. Methods. Corn plants hybrid Dostatok 300 MV in the phase of two leaves were irradiated by UV-B at doses of 1, 2, 4, 8, 16 kJ/m2 with a power of 6 W/m2 and were grown in a long day conditions. After irradiation, the growth of shoots in length, the growth of the mass of plants, the content of photosynthetic pigments and endogenous hydrogen peroxide (HP) in the leaves were determined. Results. It is shown that after irradiation of corn plants UV-B at doses of 4, 8, 16 kJ/m2 the growth of shoots in length decreased, after the irradiation of UV-B at doses of 1, 2 kJ/m2 mass of plants increased. UV-B irradiation in all doses, except for a dose of 16 kJ/m2, stimulated the accumulation of photosynthetic pigments in the leaves. Increasing HP content in the leaves was determined in corn leaves after irradiation of UV-B in all doses. Conclusions. It is shown that irradiation of young corn plants by acute UV-B at doses from 1 to 16 kJ/m2 induced adaptive reactions, that included inhibition of shoot growth with simultaneous stimulation of plants mass growth, accumulation of photosynthetic pigments, increased endogenous content of HP. The adaptive period lasted about 10 days, after that processes of growth, formation of a photosynthetic apparatus and content of HP were stabilized. UV-B belongs to the necessary components of sunlight components for corn growth. Keywords: UV-B radiation, Zea mays L., photosynthetic pigments, adaptation.

Loss of ALBINO3b Insertase Results in Truncated Light-Harvesting Antenna in Diatoms.

The family of chloroplast ALBINO3 (ALB3) proteins function in the insertion and assembly of thylakoid membrane protein complexes. Loss of ALB3b in the marine diatom Phaeodactylum tricornutum leads to a striking change of cell color from the normal brown to green. A 75% decrease of the main fucoxanthin-chlorophyll a/c-binding proteins was identified in the alb3b strains as the cause of changes in the spectral properties of the mutant cells. The alb3b lines exhibit a truncated light-harvesting antenna phenotype with reduced amounts of light-harvesting pigments and require a higher light intensity for saturation of photosynthesis. Accumulation of photoprotective pigments and light-harvesting complex stress-related proteins was not negatively affected in the mutant strains, but still the capacity for nonphotochemical quenching was lower compared with the wild type. In plants and green algae, ALB3 proteins interact with members of the chloroplast signal recognition particle pathway through a Lys-rich C-terminal domain. A novel conserved C-terminal domain was identified in diatoms and other stramenopiles, questioning if ALB3b proteins have the same interaction partners as their plant/green algae homologs.

Exposure to UV-B Radiation Leads to Increased Deposition of Cell Wall-Associated Xerocomic Acid in Cultures of Serpula himantioides.

Many fungi are thought to have developed morphological and physiological adaptations to cope with exposure to UV-B radiation, but in most species, such responses and their protective effects have not been explored. Here, we study the adaptive response to UV-B radiation in the widespread, saprotrophic fungus Serpula himantioides, frequently found colonizing coniferous wood in nature. We report the morphological and chemical responses of S. himantioides to controlled intensities of UV-B radiation, under in vitro culture conditions. Ultraviolet radiation induced a decrease in the growth rate of S. himantioides but did not cause gross morphological changes. Instead, we observed accumulation of pigments near the cell wall with increasing intensities of UV-B radiation. Nuclear magnetic resonance (NMR) and high-performance liquid chromatography-mass spectrometry (HPLC-MS) analyses revealed that xerocomic acid was the main pigment present, both before and after UV-B exposure, increasing from 7 mg/liter to 15 mg/liter after exposure. We show that xerocomic acid is a photoprotective metabolite with strong antioxidant abilities, as evidenced by DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt], and oxygen radical absorbance capacity (ORAC) assays. Finally, we assessed the capacity of xerocomic acid as a photoprotective agent on HEK293 cells and observed better photoprotective properties than those of β-carotene. Xerocomic acid is therefore a promising natural product for development as a UV-protective ingredient in cosmetic and pharmaceutical products.IMPORTANCE Our study shows the morphological and chemical responses of S. himantioides to controlled doses of UV-B radiation under in vitro culture conditions. We found that increased biosynthesis of xerocomic acid was the main strategy adopted by S. himantioides against UV-B radiation. Xerocomic acid showed strong antioxidant and photoprotective abilities, which has not previously been reported. Our results indicate that upon UV-B exposure, S. himantioides decreases its hyphal growth rate and uses this energy instead to increase the biosynthesis of xerocomic acid, which is allocated near the cell wall. This metabolic switch likely allows xerocomic acid to efficiently defend S. himantioides from UV radiation through its antioxidant and photoprotective properties. The findings further suggest that xerocomic acid is a promising candidate for development as a cosmetic ingredient to protect against UV radiation and should therefore be investigated in depth in the near future both in vitro and in vivo.

Light in the Fungal World: From Photoreception to Gene Transcription and Beyond.

Fungi see light of different colors by using photoreceptors such as the White Collar proteins and cryptochromes for blue light, opsins for green light, and phytochromes for red light. Light regulates fungal development, promotes the accumulation of protective pigments and proteins, and regulates tropic growth. The White Collar complex (WCC) is a photoreceptor and a transcription factor that is responsible for regulating transcription after exposure to blue light. In Neurospora crassa, light promotes the interaction of WCCs and their binding to the promoters to activate transcription. In Aspergillus nidulans, the WCC and the phytochrome interact to coordinate gene transcription and other responses, but the contribution of these photoreceptors to fungal photobiology varies across fungal species. Ultimately, the effect of light on fungal biology is the result of the coordinated transcriptional regulation and activation of signal transduction pathways.

A Two-Component System That Modulates Cyclic di-GMP Metabolism Promotes Legionella pneumophila Differentiation and Viability in Low-Nutrient Conditions.

During its life cycle, the environmental pathogen Legionella pneumophila alternates between a replicative and transmissive cell type when cultured in broth, macrophages, or amoebae. Within a protozoan host, L. pneumophila further differentiates into the hardy cell type known as the mature infectious form (MIF). The second messenger cyclic di-GMP coordinates lifestyle changes in many bacterial species, but its role in the L. pneumophila life cycle is less understood. Using an in vitro broth culture model that approximates the intracellular transition from the replicative to the transmissive form, here we investigate the contribution to L. pneumophila differentiation of a two-component system (TCS) that regulates cyclic di-GMP metabolism. The TCS is encoded by lpg0278-lpg0277 and is cotranscribed with lpg0279, which encodes a protein upregulated in MIF cells. The promoter for this operon is RpoS dependent and induced in nutrient-limiting conditions that do not support replication, as demonstrated using a gfp reporter and quantitative PCR (qPCR). The response regulator of the TCS (Lpg0277) is a bifunctional enzyme that both synthesizes and degrades cyclic di-GMP. Using a panel of site-directed point mutants, we show that cyclic di-GMP synthesis mediated by a conserved GGDEF domain promotes growth arrest of replicative L. pneumophila, accumulation of pigment and poly-3-hydroxybutyrate storage granules, and viability in nutrient-limiting conditions. Genetic epistasis tests predict that the MIF protein Lpg0279 acts as a negative regulator of the TCS. Thus, L. pneumophila is equipped with a regulatory network in which cyclic di-GMP stimulates the switch from a replicative to a resilient state equipped to survive in low-nutrient environments.IMPORTANCE Although an intracellular pathogen, L. pneumophila has developed mechanisms to ensure long-term survival in low-nutrient aqueous conditions. Eradication of L. pneumophila from contaminated water supplies has proven challenging, as outbreaks have been traced to previously remediated systems. Understanding the genetic determinants that support L. pneumophila persistence in low-nutrient environments can inform design and assessment of remediation strategies. Here we characterize a genetic locus that encodes a two-component signaling system (lpg0278-lpg0277) and a putative regulator protein (lpg0279) that modulates the production of the messenger molecule cyclic di-GMP. We show that this locus promotes both L. pneumophila cell differentiation and survival in nutrient-limiting conditions, thus advancing the understanding of the mechanisms that contribute to L. pneumophila environmental resilience.

Penatalaksanaan Perawatan Hiperpigmentasi Pada Gingiva Dengan Metode Scrapping Menggunakan Pisau Bedah: Studi Kasus

Hyperpigmentation is a disorder of the gingiva caused by various factors including heredity, disease, drugs, smoking habits. This can occur because of the accumulation of melanin pigment in the basal gingival layer resulting in a brownish or blackish color on the surface of the gingiva which when viewed aesthetically is not good because it is not like the normal gingival color of coral pink. Objective: to get the gingival color back to normal, namely coral pink. Management in cases of pigmentation using the surgical method by scrapping using a scalpel No.15. In this study there were 3 cases, namely, case 1, a 20-year-old female patient had genetic or genetic hyperpigmentation. Case 2, a 27-year-old male patient had genetic or genetic hyperpigmentation. Case 3, a 24-year-old female patient had gingival pigmentation due to smoking habits. The results of surgical management in all three cases, namely the gingival depigmentation method by scrapping gave a good esetetic result, but for gingival hyperpigmentation in cases 1 and 2 it could recur later.

Susceptibility of maize genotypes to Rhyzopertha dominica (F.)

This work examined the survival of Rhyzopertha dominica on maize kernels differing either for specific traits or for their genetic background. Maize traits comprised endosperm starch composition, and accumulation of pigments, i.e., carotenoids and anthocyanins, in the aleurone, while maize genotypes included the B73 reference line, the high oil content RAlexo line and the commercial variety Zea mays everta (popcorn). Kernels of the different genotypes were classified according to the endosperm texture. The number of adults of R. dominica developing from neonate larvae on both whole and sectioned kernels was measured. Differences were only observed in experiments with whole kernels. The lowest value was observed for the B73 line, and the highest for the popcorn variety. These two genotypes have the lowest and highest proportions of vitreous endosperm, respectively. In our experimental conditions, variations in the insect attack were observed in different lines, thus indicating that the insect–kernel interaction is influenced by quantitative more than single-gene traits.

Forensic age estimation based on the pigmentation in the costal cartilage from human mortal remains.

Age estimation is considered a crucial and challenging issue in forensic casework. Costal cartilage appears a potential mortal remain in age-at-death estimation attributable to its correlative alteration in color based on pigment accumulation with the advancing age. In this study, samples from the second costal cartilage were collected in a Chinese Han population, and the cross sections were subsequently scanned and digitalized in a standard way. Color change was quantified using mean gray value (MGV), which was measured by Photoshop CS5. After the exclusion of samples with factors which could impair the quality of images and the accuracy of values, a high correlation was demonstrated between age and MGV in samples. A linear regression model (AGE = 173.425-0.755*aveMGV) was established for age prediction, with its performance evaluated using both samples from the training set and the blind test set, in which a mean absolute deviation of 4.42 years and 3.57 years was obtained, respectively. Altogether, MGV could be reckoned as a precise quantification of pigmentation in costal cartilage and an excellent indicator of age prediction in the age interval from 20 to 60 years. Moreover, our strategy appears more user-friendly and accurate, thus exceedingly practical for age estimation in forensic anthropology.

Low dose cadmium (II) induced antifungal activity against blast disease in rice

The present approach in this study aims to check infection of Pyricularia oryzae (MTCC-1477) in a rice cultivar (Khandagiri) by applying low dose (50 μM) cadmium (II). In co-stress of Pyricularia oryzae and cadmium, the plants showed increased growth of shoot length and accumulation of protein, reducing sugar, photosynthetic pigments and antioxidative enzymes indicating improved growth and development at par with control plants. The co-stress induced increase in Phenylammonia lyase activity up to 752.01 U/mg protein and decrease in lipid peroxidation up to 15.81 μg/g, this activity strengthen the idea of enhanced innate defense mechanism of the plant against the pathogen. Antioxidant enzymes demonstrated enhanced activity and number of isoforms in co-stress indicative index for better performance. Two protein bands of MW ~23 kDa and ~47 kDa were more pronounced in the fungal and Cd treatment respectively. But the most affected band of MW ~23 kDa disappeared due to co-stress, which may be designated as a Pathogen Related protein. The study under present experimental conditions is a trade off approach to next generation sustainable agriculture keeping in mind about rapid changing climate and alarming growth of environmental pollution.

Conserved Biochemical Defenses Underpin Host Responses to Oomycete Infection in an Early-Divergent Land Plant Lineage

The expansion of plants onto land necessitated theevolution of robust defense strategies to protect against a wide array of microbial invaders. Whereas host responses to microbial colonization are extensively explored in evolutionarily young land plant lineages such as angiosperms, we know relatively little about plant-pathogen interactions in early-diverging land plants thought to better represent the ancestral state. Here, we define the transcriptional and proteomic response of the early-divergent liverwort Marchantia polymorpha to infection with the oomycete pathogen Phytophthora palmivora. We uncover a robust molecular response to oomycete colonization in Marchantia that consists of conserved land plant gene families. Direct macroevolutionary comparisons of host infection responses in Marchantia and the model angiosperm Nicotiana benthamiana further reveal a shared set of orthologous microbe-responsive genes that include members of the phenylpropanoid metabolic pathway. In addition, we identify a role for the Marchantia R2R3-MYB transcription factor MpMyb14 in activating phenylpropanoid (flavonoid) biosynthesis during oomycete infection. Mpmyb14 mutants infected with P.palmivora fail toactivate phenylpropanoid biosynthesis gene expression and display enhanced disease susceptibility compared to wild-type plants. Conversely, the ectopic induction of MpMyb14 led to the accumulation of anthocyanin-like pigments and dramatically enhanced liverwort resistance to P.palmivora infection. Collectively, our results demonstrate that the Marchantia response to oomycete infection displays evolutionarily conserved features indicative of an ancestral pathogen deterrence strategy centered on phenylpropanoid-mediated biochemical defenses.

The MYB5-driven MBW complex recruits a WRKY factor to enhance the expression of targets involved in vacuolar hyper-acidification and trafficking in grapevine.

The accumulation of secondary metabolites and the regulation of tissue acidity contribute to the important traits of grape berry and influence plant performance in response to abiotic and biotic factors. In several plant species a highly conserved MYB-bHLH-WD (MBW) transcriptional regulatory complex controls flavonoid pigment synthesis and transport, and vacuolar acidification in epidermal cells. An additional component, represented by a WRKY-type transcription factor, physically interacts with the complex increasing the expression of some target genes and adding specificity for other targets. Here we investigated the function of MBW(W) complexes involving two MYBs (VvMYB5a and VvMYB5b) and the WRKY factor VvWRKY26 in grapevine (Vitis vinifera L.). Using transgenic grapevine plants we showed that these complexes affected different aspects of morphology, plant development, pH regulation, and pigment accumulation. Transcriptomic analysis identified a core set of putative target genes controlled by VvMYB5a, VvMYB5b, and VvWRKY26 in different tissues. Our data indicated that VvWRKY26 enhances the expression of selected target genes induced by VvMYB5a/b. Among these targets are genes involved in vacuolar hyper-acidification, such as the P-type ATPases VvPH5 and VvPH1, and trafficking, and genes involved in the biosynthesis of flavonoids. In addition, VvWRKY26 is recruited specifically by VvMYB5a, reflecting the functional diversification of VvMYB5a and VvMYB5b. The expression of MBWW complexes in vegetative organs, such as leaves, indicates a possible function of vacuolar hyper-acidification in the repulsion of herbivores and/or in developmental processes, as shown by defects in transgenic grape plants where the complex is inactivated.

The use of industrial waste materials for alleviation of iron deficiency in sunflower and maize

PurposeThe aim of this study was to prove that the Fe-containing by-products (compost, sewage and lime sludge) have potential influence on the correction of Fe deficiency in sunflower and maize.MethodsThe physiological parameters used were the dry matter (DM), the relative chlorophyll content, and the content of photosynthesis pigments (chlorophyll a, chlorophyll b and carotenoids).ResultsThe results showed that sewage sludge was effective even when applied at low concentration (2 g L−1) for both sunflower and maize plants. In maize, however, chlorophyll a was the only pigment induced after sewage sludge treatments in contrast to sunflower, which could be the reason for lower DM in maize. Compost could only be effective when applied at higher concentrations (4 g L−1) for sunflower because of its low-Fe content, further showing that maize plants require more Fe. Despite its high-Fe content, lime sludge could not be effective in alleviating Fe deficiency for both sunflower and maize plants because of its high pH, which makes Fe unavailable for uptake by the plants.ConclusionsAlthough the investigated by-products can be hazardous depending on their origin, their use as micro-element fertilizer can be a very economical way of utilization in the agricultural fields, which may limit the use of high quantities of expensive Fe-containing fertilizers. Among the three waste products, sewage sludge application proved to have a great potential of correcting Fe deficiency by inducing accumulation of the photosynthesis pigments, leading to high photosynthesis and eventually high DM.

Regulation of ectopic heterochromatin-mediated epigenetic diversification by the JmjC family protein Epe1.

H3K9 methylation (H3K9me) is a conserved marker of heterochromatin, a transcriptionally silent chromatin structure. Knowledge of the mechanisms for regulating heterochromatin distribution is limited. The fission yeast JmjC domain-containing protein Epe1 localizes to heterochromatin mainly through its interaction with Swi6, a homologue of heterochromatin protein 1 (HP1), and directs JmjC-mediated H3K9me demethylation in vivo. Here, we found that loss of epe1 (epe1Δ) induced a red-white variegated phenotype in a red-pigment accumulation background that generated uniform red colonies. Analysis of isolated red and white colonies revealed that silencing of genes involved in pigment accumulation by stochastic ectopic heterochromatin formation led to white colony formation. In addition, genome-wide analysis of red- and white-isolated clones revealed that epe1Δ resulted in a heterogeneous heterochromatin distribution among clones. We found that Epe1 had an N-terminal domain distinct from its JmjC domain, which activated transcription in both fission and budding yeasts. The N-terminal transcriptional activation (NTA) domain was involved in suppression of ectopic heterochromatin-mediated red-white variegation. We introduced a single copy of Epe1 into epe1Δ clones harboring ectopic heterochromatin, and found that Epe1 could reduce H3K9me from ectopic heterochromatin but some of the heterochromatin persisted. This persistence was due to a latent H3K9me source embedded in ectopic heterochromatin. Epe1H297A, a canonical JmjC mutant, suppressed red-white variegation, but entirely failed to remove already-established ectopic heterochromatin, suggesting that Epe1 prevented stochastic de novo deposition of ectopic H3K9me in an NTA-dependent but JmjC-independent manner, while its JmjC domain mediated removal of H3K9me from established ectopic heterochromatin. Our results suggest that Epe1 not only limits the distribution of heterochromatin but also controls the balance between suppression and retention of heterochromatin-mediated epigenetic diversification.

Two transcription factors cooperatively regulate DHN melanin biosynthesis and development in Pestalotiopsis fici.

Fungal 1,8-dihydroxynaphthalene (DHN) melanin plays important roles in UV protection, oxidative stress and pathogenesis. However, knowledge of the regulatory mechanisms of its biosynthesis is limited. Previous studies showed two transcription factors, PfmaF and PfmaH, located in the DHN melanin biosynthetic gene cluster (Pfma) in Pestalotiopsis fici. In this study, deletion of PfmaH resulted in loss of melanin and affected conidia cell wall integrity. Specifically, PfmaH directly regulates the expression of scytalone dehydratase, which catalyzes the transition of scytalone to T3 HN. However, PfmaF disruption using CRISPR/Cas9 system affected neither DHN melanin distribution nor conidia cell wall integrity in P. fici. Unexpectedly, overexpression of PfmaF leads to heavy pigment accumulation in P. fici hyphae. Transcriptome and qRT-PCR analyses provide insight into the roles of PfmaF and PfmaH in DHN melanin regulation. PfmaH, as a pathway specific regulator, mainly regulates melanin biosynthesis that contributes to cell wall development. Furthermore, PfmaF functions as a broad regulator to stimulate PfmaH expression in melanin production, secondary metabolism as well as fungal development.

Lifespan Extending and Oxidative Stress Resistance Properties of a Leaf Extracts from Anacardium occidentale L. in Caenorhabditis elegans.

Anacardium occidentale (AO) contains a number of polyphenolic secondary metabolites with antioxidant activity. The objectives of this study were aimed at investigating the roles of AO leaf extracts in antioxidative stress and longevity, as well as their underlying mechanisms, in the Caenorhabditis elegans (C. elegans) model. AO extracts mediated the survival rate of nematodes under oxidative stress by attenuating intracellular reactive oxygen species (ROS) via the DAF-16/FoxO and SKN-1/Nrf-2 signaling pathways. AO extracts stimulated the expression of stress response genes including SOD-3 and GST-4. Moreover, AO extracts exhibited antiaging activities and enhanced longevity. We observed improved pharyngeal pumping function, attenuation of pigment accumulation (lipofuscin), and an increased lifespan of the worms. Collectively, our results demonstrated that AO extracts exerted both oxidative stress resistance and antiaging properties in the C. elegans model and may lead to new agents to benefit humans in the near future.

Targeted photosensitizer delivery: A prospective approach to vitiligo photochemotherapy

Aim. In this work, the authors set out to develop an effective method for the intrafollicular delivery of “Ammi majus fructuum furocumarines” photosensitizer (AMFF) followed by UVA irradiation (λ = 320–400 nm). Materials and methods. The proposed delivery method consists in using calcium carbonate particles acting as AMFF carriers. In vivo monitoring of hair follicle filling was carried out via optical coherence tomography, as well as by means of analyzing epilated hair using confocal laser scanning microscopy. Following the administration of free and encapsulated AMFF to three healthy volunteers, the character of UVA-induced skin pigmentation was registered under dermatoscopic examination. Results. The obtained results demonstrate a profuse filling of hair follicles with calcium carbonate particles, thus confirming the possibility of intrafollicular photosensitizer delivery. It was established that exposure to UVA irradiation causes intense pigment accumulation in the area of AMFF carrier administration. Conclusion. The proposed method of the targeted photosensitizer delivery allows photochemical therapy to be improved.

Abscisic acid and ethylene biosynthesis-related genes are associated with anthocyanin accumulation in purple ornamental cabbage (Brassica oleracea var. acephala).

Purple ornamental cabbage (Brassica oleracea var. acephala) is a popular decorative plant, cultivated for its colorful leaf rosettes that persist in cool weather. It is characterized by green outer leaves and purple inner leaves, whose purple pigmentation is due to the accumulation of anthocyanin pigments. Phytohormones play important roles in anthocyanin biosynthesis in other species. Here, we identified 14 and 19 candidate genes putatively involved in abscisic acid (ABA) and ethylene (ET) biosynthesis, respectively, in B. oleracea. We determined the expression patterns of these candidate genes by reverse-transcription quantitative PCR (RT-qPCR). Among candidate ABA biosynthesis-related genes, the expressions of BoNCED2.1, BoNCED2.2, BoNCED6, BoNCED9.1, and BoAAO3.2 were significantly higher in purple compared to green leaves. Likewise, most of the ET biosynthetic genes (BoACS6, BoACS9.1, BoACS11, BoACO1.1, BoACO1.2, BoACO3.1, BoACO4, and BoACO5) had significantly higher expression in purple compared to green leaves. Among these genes, BoNCED2.1, BoNCED2.2, BoACS11, and BoACO4 showed particularly strong associations with total anthocyanin content of the purple inner leaves. Our results suggest that ABA and ET might promote the intense purple pigmentation of the inner leaves of purple ornamental cabbage.

Growth, biochemical composition, and photosynthetic performance of Scenedesmus acuminatus during nitrogen starvation and resupply

Many microalgae store energy as triacylglycerols under certain environmental conditions. Nitrogen limitation is recognized as an efficient lipid-accumulation trigger in microalgae. Here, biochemical composition (lipids, carbohydrates, and soluble proteins) time courses, fatty acid composition, pigment accumulation, and the photosynthetic efficiency of photosystem II (PSII) in Scenedesmus acuminatus were investigated under nitrogen starvation and resupply conditions. This work provides a theoretical basis for how microalgae utilize nitrogen to optimize lipid production. Nitrogen starvation inhibits cell division and growth, and promote the accumulation of lipids and carbohydrates. The total lipid content under nitrogen starvation approached 50.12% of the dry weight and neutral lipids accounted for 92.55% of the total lipids. Upon NaNO3 supplementation at day 9, the maximum photosynthesis efficiency (Fv/Fm), and the total amino acid, soluble protein, and pigment levels recovered rapidly within the first 12 h, while the degraded carbohydrate served as a carbon and energy source. After a 2-day lag time (from days 9 to 11), the biomass increased rapidly. The biomass concentration and lipid content reached 4.24 g L−1 and 36.46% of dry weight, respectively, at the end of cultivation. The Chla and Chlb contents of S. acuminatus were more sensitive than the carotenoid content to environmental nitrogen sources. The change in non-photochemical quenching (NPQ) was complicated, significantly increasing to a peak and then decreasing during both nitrogen starvation and recovery.

Acetylcholine mechanism of action to enhance tolerance to salt stress in Nicotiana benthamiana

Acetylcholine (ACh) is one of the important neurotransmitters, involved in signal transduction function in human and animal brain. However, the influence of ACh treatment on salt-stress tolerance in plants is yet unknown. Salt stress caused a reduction in gas-exchange parameters, chlorophyll content, antioxidant enzyme activities, and leaf relative water content of Nicotiana benthamiana plants. However, the above inhibitions could be significantly alleviated by application of leaf spray or root application of ACh. Exogenous ACh reduced the accumulation of malondialdehyde by enhancing activities of antioxidant enzymes such as peroxidase and superoxide dismutase. In addition, enhanced accumulation of organic osmolytes including soluble sugars and proline possibly regulated the signal mechanisms related to stress. Application of ACh could also improve gas-exchange parameters and photosynthetic pigment accumulation in leaves of salt-stressed plants. These effects of ACh were beneficial for maintaining better water status in plants, the concentration of 10 µM ACh applied both in the form of leaf spray or root application was the most effective. Therefore, our findings provided a stronger evidence for a physiological role of ACh and its potential use at optimal concentration by leaf or root application to alleviate damage caused by salt-stress in plants.

The multi-allelic APRR2 gene is associated with fruit pigment accumulation in melon and watermelon

Color and pigment contents are important aspects of fruit quality and consumer acceptance of cucurbit crops. Here, we describe the independent mapping and cloning of a common causative APRR2 gene regulating pigment accumulation in melon and watermelon. We initially show that the APRR2 transcription factor is causative for the qualitative difference between dark and light green rind in both crops. Further analyses establish the link between sequence or expression level variations in the CmAPRR2 gene and pigment content in the rind and flesh of mature melon fruits. A genome-wide association study (GWAS) of young fruit rind color in a panel composed of 177 diverse melon accessions did not result in any significant association, leading to an earlier assumption that multiple genes are involved in shaping the overall phenotypic variation in this trait. Through resequencing of 25 representative accessions and allelism tests between light rind accessions, we show that multiple independent single nucleotide polymorphisms in the CmAPRR2 gene are causative of the light rind phenotype. The multi-haplotypic nature of this gene explains the lack of detection power obtained through genotyping by sequencing-based GWAS and confirms the pivotal role of this gene in shaping fruit color variation in melon. This study demonstrates the power of combining bi- and multi-allelic designs with deep sequencing, to resolve lack of power due to high haplotypic diversity and low allele frequencies. Due to its central role and broad effect on pigment accumulation in fruits, the APRR2 gene is an attractive target for carotenoid bio-fortification of cucurbit crops.