The flesh color of Cucumis melo (melon) is genetically determined, and can be white, light green or orange, with β–carotene being the predominant pigment. We associated carotenoid accumulation in ...melon fruit flesh with polymorphism within CmOr, a homolog of the cauliflower BoOr gene, and identified CmOr as the previously described gf locus in melon. CmOr was found to co‐segregate with fruit flesh color, and presented two haplotypes (alleles) in a broad germplasm collection, one being associated with orange flesh and the second being associated with either white or green flesh. Allelic variation of CmOr does not affect its transcription or protein level. The variation also does not affect its plastid subcellular localization. Among the identified single nucleotide polymorphisms (SNPs) between CmOr alleles in orange versus green/white‐flesh fruit, a single SNP causes a change of an evolutionarily highly conserved arginine to histidine in the CmOr protein. Functional analysis of CmOr haplotypes in an Arabidopsis callus system confirmed the ability of the CmOr orange haplotype to induce β–carotene accumulation. Site‐directed mutagenesis of the CmOr green/white haplotype to change the CmOR arginine to histidine triggered β–carotene accumulation. The identification of the ‘golden’ SNP in CmOr, which is responsible for the non‐orange and orange melon fruit phenotypes, provides new tools for studying the Or mechanism of action, and suggests genome editing of the Or gene for nutritional biofortification of crops.
Premise of the Study
The domestication history of melon is still unclear. An African or Asian origin has been suggested, but its closest wild relative was recently revealed to be an Australian ...species. The complicated taxonomic history of melon has resulted in additional confusion, with a high number of misidentified germplasm collections currently used by breeders and in genomics research.
Methods
Using seven DNA regions sequenced for 90% of the genus and the major cultivar groups, we sort out described names and infer evolutionary origins and domestication centers.
Key Results
We found that modern melon cultivars go back to two lineages, which diverged ca. 2 million years ago. One is restricted to Asia (Cucumis melo subsp. melo), and the second, here described as C. melo subsp. meloides, is restricted to Africa. The Asian lineage has given rise to the widely commercialized cultivar groups and their market types, while the African lineage gave rise to cultivars still grown in the Sudanian region. We show that C. trigonus, an overlooked perennial and drought‐tolerant species from India is among the closest living relatives of C. melo.
Conclusions
Melon was domesticated at least twice: in Africa and Asia. The African lineage and the Indian C. trigonus are exciting new resources for breeding of melons tolerant to climate change.
Cadmium (Cd), prevailing in most of the agricultural lands of the world contaminates food chain, thereby causing several health implications. It has become the main heavy metal contaminant in most of ...the agricultural lands of Pakistan due to the widespread use of phosphate fertilizers besides application of irrigation water contaminated with industrial and mining effluents. Plant growth promoting bacteria (PGPB) are capable to enhance growth and metal stress tolerance in supplemented plants. Zinc oxide nanoparticles (ZnO-NPs) are capable to alleviate various abiotic stresses when applied to plants. During current research, the efficacy of single and combined application of Bacillus fortis IAGS 223 and ZnO-NPs was evaluated for alleviation of Cd (75 mg kg−1) induced phytotoxicity in Cucumis melo plants. For this purpose, C. melo plants, subjected to Cd stress were treated with B. fortis IAGS 223 and ZnO-NPs (20 mg kg−1), either alone or in combination. The growth relevant characteristics including photosynthetic pigments, hydrogen peroxide (H2O2), malondialdehyde (MDA), and activities of antioxidative enzymes as well as Zn and Cd contents in treated plants were examined. The individual application of ZnO-NPs and B. fortis IAGS 223 slightly enhanced all the above-mentioned growth characteristics in plants under Cd stress. However, the combined application of ZnO-NPs and B. fortis IAGS-223 considerably modulated the activity of antioxidant enzymes besides upgradation of the biochemicals and growth parameters of Cd stressed plants. The decreased amount of stress markers such as H2O2, and MDA in addition with reduction of Cd contents was observed in shoots of ZnO-NPs and B. fortis IAGS-223 applied plants. B. fortis IAGS-223 inoculated plants supplemented with ZnO-NPs, exhibited reduced amount of Cd as well as protein bound thiols and non-protein bound thiols under Cd stress. Subsequently, the reduced Cd uptake improved growth of ZnO-NPs and B. fortis IAGS-223 applied plants. Henceforth, field trials may be performed to formulate appropriate combination of ZnO-NPs and B. fortis IAGS-223 to acquire sustainable crop production under Cd stress.
•Cd-stress reduced growth of C. melo plants.•B. fortis IAGS 223 and Zno-NPs mitigated Cd stress.•B. fortis IAGS 223 and Zno-NPs modulated antioxidant system of plants.•B. fortis IAGS 223 and Zno-NPs exhibited synergistic effect.
Aphis gossypii is a polyphagous sucking aphid and a vector for many viruses. In Cucumis melo, a dominant locus, Vat, confers a high level of resistance to Aphis gossypii infestation and to viruses ...transmitted by this vector. To investigate the mechanism underlying this double resistance, we first genetically dissected the Vat locus. We delimited the double resistance to a single gene that encodes for a coiled‐coil–nucleotide‐binding‐site–leucine‐rich repeat (CC‐NBS‐LRR) protein type. To validate the genetic data, transgenic lines expressing the Vat gene were generated and assessed for the double resistance. In this analysis, Vat‐transgenic plants were resistant to A. gossypii infestation as well as A. gossypii‐mediated virus transmission. When the plants were infected mechanically, virus infection occurred on both transgenic and non‐transgenic control plants. These results confirmed that the cloned CC‐NBS‐LRR gene mediates both resistance to aphid infestation and virus infection using A. gossypii as a vector. This resistance also invokes a separate recognition and response phases in which the recognition phase involves the interaction of an elicitor molecule from the aphid and Vat from the plant. The response phase is not specific and blocks both aphid infestation and virus infection. Sequence analysis of Vat alleles suggests a major role of an unusual conserved LRR repeat in the recognition of A. gossypii.
CmTST2 is a tonoplast sugar transporter that is highly expressed during melon fruit development, and its overexpression also increases sugar accumulation in strawberry and cucumber fruits.
Abstract
...Fruits are an important part of the human diet and sugar content is a major criterion used to evaluate fruit quality. Melon fruit accumulate high sugar concentrations during their development; however, the mechanism through which these sugars are transported into the vacuoles of fruit cells for storage remains unclear. In this study, three tonoplast sugar transporters (TSTs), CmTST1, CmTST2, and CmTST3, were isolated from melon plants. Analysis of subcellular localization revealed that all these proteins were targeted to the tonoplast, and evaluation of spatial expression and promoter-GUS activity indicated that they had different expression patterns in the plant. RT-PCR and qRT-PCR results indicated that CmTST2 exhibited the highest expression level among the TST isoforms during melon fruit development. Histochemical and immunohistochemistry localization experiments were performed to identify the tissue- and cell-type localization of CmTST2 in the fruit, and the results indicated that both its transcription and translation were in the mesocarp and vascular cells. Overexpressing the CmTST2 gene in strawberry fruit and cucumber plants by transient expression and stable transformation, respectively, both increased sucrose, fructose, and glucose accumulation in the fruit. The results indicate that CmTST2 plays an important role in sugar accumulation in melon fruit.
The unique aroma of melons (Cucumis melo L., Cucurbitaceae) is composed of many volatile compounds biosynthetically derived from fatty acids, carotenoids, amino acids, and terpenes. Although amino ...acids are known precursors of aroma compounds in the plant kingdom, the initial steps in the catabolism of amino acids into aroma volatiles have received little attention. Incubation of melon fruit cubes with amino acids and α-keto acids led to the enhanced formation of aroma compounds bearing the side chain of the exogenous amino or keto acid supplied. Moreover, L-13C6phenylalanine was also incorporated into aromatic volatile compounds. Amino acid transaminase activities extracted from the flesh of mature melon fruits converted L-isoleucine, L-leucine, L-valine, L-methionine, or L-phenylalanine into their respective α-keto acids, utilizing α-ketoglutarate as the amine acceptor. Two novel genes were isolated and characterized (CmArAT1 and CmBCAT1) encoding 45.6 kDa and 42.7 kDa proteins, respectively, that displayed aromatic and branched-chain amino acid transaminase activities, respectively, when expressed in Escherichia coli. The expression of CmBCAT1 and CmArAT1 was low in vegetative tissues, but increased in flesh and rind tissues during fruit ripening. In addition, ripe fruits of climacteric aromatic cultivars generally showed high expression of CmBCAT1 and CmArAT1 in contrast to non-climacteric non-aromatic fruits. The results presented here indicate that in melon fruit tissues, the catabolism of amino acids into aroma volatiles can initiate through a transamination mechanism, rather than decarboxylation or direct aldehyde synthesis, as has been demonstrated in other plants.
The cucurbit powdery mildew elicited by Podosphaera xanthii is one of the most important limiting factors in cucurbit production. Our knowledge of the genetic and molecular bases underlying the ...physiological processes governing this disease is very limited. We used RNA-sequencing to identify differentially expressed genes in leaves of Cucumis melo upon inoculation with P. xanthii, using RNA samples obtained at different time points during the early stages of infection and their corresponding uninfected controls. In parallel, melon plants were phenotypically characterized using imaging techniques. We found a high number of differentially expressed genes (DEGs) in infected plants, which allowed for the identification of many plant processes that were dysregulated by the infection. Among those, genes involved in photosynthesis and related processes were found to be upregulated, whereas genes involved in secondary metabolism pathways, such as phenylpropanoid biosynthesis, were downregulated. These changes in gene expression could be functionally validated by chlorophyll fluorescence imaging and blue-green fluorescence imaging analyses, which corroborated the alterations in photosynthetic activity and the suppression of phenolic compound biosynthesis. The powdery mildew disease in melon is a consequence of a complex and multifaceted process that involves the dysregulation of many plant pathways such as primary and secondary metabolism.
Water deficiency up to a certain level and duration leads to a stress condition called drought. It is a multi-dimensional stress causing alteration in the physiological, morphological, biochemical, ...and molecular traits in plants resulting in improper plant growth and development. Drought is one of the major abiotic stresses responsible for loss of crops including muskmelon (Cucumis melo. L). Muskmelon genotype SC-15, which exhibits high drought resistance as reported in our earlier reports, was exposed to deficient water condition and studied for alteration in physiological, molecular and proteomic profile changes in the leaves. Drought stress results in reduced net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration (E) rate. With expanded severity of drought, declination recorded in content of total chlorophyll and carotenoid while enhancement observed in phenol content indicating generation of oxidative stress. In contrary, activities of catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), and guaiacol (POD) were increased under drought stress. Peptide mass fingerprinting (PMF) showed that drought increased the relative abundance of 38 spots while decreases10 spots of protein. The identified proteins belong to protein synthesis, photosynthesis, nucleotide biosynthesis, stress response, transcription regulation, metabolism, energy and DNA binding. A drought-induced MADS-box transcription factor was identified. The present findings indicate that under drought muskmelon elevates the abundance of defense proteins and suppresses catabolic proteins. The data obtained exhibits possible mechanisms adopted by muskmelon to counter the impacts of drought induced stress.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Methylthioacetic acid (MTA) is an acid-hydrolyzed derivative of a natural aroma compound, methylthioacetic acid ethyl ester isolated from Cucumis melo var. conomon (Katsura-uri, Japanese Picking ...Melon), and induces a villiform-like structure dome in RCM-1 human colorectal cancer cell culture. Thus far, the physiological and molecular properties of MTA-mediated dome formation remain unknown. Herein, MTA (not more than 2 mM) was demonstrated to differentiate the unorganized cell mass into the dome in RCM-1 cell culture by disclosing the correlation between dome formation and several intestinal differentiation markers such as alkaline phosphatase activity and the protein levels of dipeptidyl peptidase 4, villin, and Krüppel-like factor 4. Dome formation in RCM-1 cell culture was additively enhanced by the simultaneous administration of MTA and butyric acid (BA), suggesting that MTA directs the differentiation of RCM-1 cells, potentially through the same or similar pathway(s) shared with BA. Notably, a high dose of MTA (2 mM or more) elevated several apoptosis markers, such as DNA fragmentation, caspase-3/7 activity, and cleavage of poly(ADP-ribose) polymerase. Altogether, in addition to RCM-1 cell differentiation, MTA triggers apoptosis. These results indicate that MTA is a potential anticarcinogenic agent applicable in differentiation therapy and traditional chemotherapy against colorectal cancers.
We investigated the effect on melon fruits of "fish water" alone or in combination with a supplement of synthetic fertilizers in a nutrient solution or foliar application of Ca(NO
)
. These ...treatments were compared with a traditional soilless system with synthetic fertilizers and no reuse of the nutrient solution. The results show that the treatments with recirculation of fish water and with the foliar supplement yielded fruits of greater weight and size but with reduced lightness and lower concentrations of proteins, NO
, K
, and total amino acids. The supply of synthetic nutrients to the roots or leaves caused a reduction in the sugar concentrations and the antioxidant activity of these fruits. The use of fish water (alone or with an amendment) increased spermine and putrescine with respect to the traditional soilless crop management. The results for these bioactive compounds in melons should be considered for maintenance of health with age.
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