Dataset Information

Sex-Dependent Variation of Pumpkin (Cucurbita maxima cv. Big Max) Nectar and Nectaries as Determined by Proteomics and Metabolomics.

ABSTRACT: Nectar is a floral reward that sustains mutualisms with pollinators, which in turn, improves fruit set. While it is known that nectar is a chemically complex solution, extensive identification and quantification of this complexity has been lacking. Cucurbita maxima cv. Big Max, like many cucurbits, is monoecious with separate male and female flowers. Attraction of bees to the flowers through the reward of nectar is essential for reproductive success in this economically valuable crop. In this study, the sex-dependent variation in composition of male and female nectar and the nectaries were defined using a combination of GC-MS based metabolomics and LC-MS/MS based proteomics. Metabolomics analysis of nectar detected 88 metabolites, of which 40 were positively identified, and includes sugars, sugar alcohols, aromatics, diols, organic acids, and amino acids. There are differences in 29 metabolites between male and female nectar. The nectar proteome consists of 45 proteins, of which 70% overlap between nectar types. Only two proteins are unique to female nectar, and 10 are specific to male nectar. The nectary proteome data, accessible at ProteomeXchange with identifier PXD009810, contained 339 identifiable proteins, 71% of which were descriptively annotatable by homology to Plantae. The abundance of 45 proteins differs significantly between male and female nectaries, as determined by iTRAQ labeling. This rich dataset significantly expands the known complexity of nectar composition, supports the hypothesis of H+-driven nectar solute export, and provides genetic and chemical targets to understand plant-pollinator interactions.

SUBMITTER: Chatt EC

PROVIDER: S-EPMC6034135 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Publications

Sex-Dependent Variation of Pumpkin (<i>Cucurbita maxima</i> cv. Big Max) Nectar and Nectaries as Determined by Proteomics and Metabolomics.

Chatt Elizabeth C EC von Aderkas Patrick P Carter Clay J CJ Smith Derek D Elliott Monica M Nikolau Basil J BJ

Frontiers in plant science 20180629

Nectar is a floral reward that sustains mutualisms with pollinators, which in turn, improves fruit set. While it is known that nectar is a chemically complex solution, extensive identification and quantification of this complexity has been lacking. <i>Cucurbita maxima</i> cv. Big Max, like many cucurbits, is monoecious with separate male and female flowers. Attraction of bees to the flowers through the reward of nectar is essential for reproductive success in this economically valuable crop. In ...[more]

PMID: 30008725

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Project description:Cucurbita maxima c.v. Big Max is a monoecious plant with separate male and female flowers which utilizes nectar as a floral reward for the attraction of bees to the flowers. Maintenance of this mutualism with bees is essential for the reproductive success in this economically valuable crop. In this study, the sex-dependent variation in composition of male and female nectar and the nectaries were defined using a combination of GC-MS based metabolomics and LC-MS/MS based proteomics. Nectar proteins were detected non-quantitatively using LC-MS/MS coupled to Orbitrap. The male and female nectary proteomes were quantified using iTRAQ labeled peptides which were fractioned and concatenated prior to detection using LC-MS/MS coupled to Orbitrap. The nectar proteome consists of 46 proteins, of which 70% overlap between nectar types. Only two proteins are unique to female nectar, and 10 are specific to male nectar. Nectarins (nectar proteins) commonly alter nectar carbohydrates. In our datasets, significant differences in carbohydrate abundance, specifically galactose and sucrose, may be explained by the unique presence of galactinol--sucrose galactosyltransferase 2 (functioning in galactose metabolism) and invertase (catalyzes the hydrolysis of sucrose to glucose and fructose) in the nectar of female and male flowers respectively. The nectary proteome contained 339 identifiable proteins, 71% of which were descriptively annotatable by homology to Plantae. The abundance of 45 proteins differs significantly between male and female nectaries. GO slim analysis revealed a high abundance of proteins related to transport, protein metabolism, carbohydrate metabolism, response to stress, and amino acid metabolism. Comparisons of relative protein abundance revealed that 45 proteins displayed differential expression between male and female nectaries (p-value <0.05); 20 of these proteins were more abundant in male nectaries and 25 were more abundant in female nectaries. GO enrichment of nectary proteins with increased female abundances indicate that female-enriched GO terms are associated with proteins functioning as plasma membrane proton pumps and central metabolism. Proteins associated with male nectary-enriched GO terms were related to cinnamic acid biosynthesis and neutralization of superoxide radicals and hydrogen peroxide.

Project description:: Sex expression is a complex process, and in-depth knowledge of its mechanism in pumpkin is important. In this study, young shoot apices at the one-true-leaf stage and 10-leaf stage in Cucurbita maxima trimonoecious line '2013-12' and subandroecious line '9-6' were collected as materials, and transcriptome sequencing was performed using an Illumina HiSeqTM 2000 System. 496 up-regulated genes and 375 down-regulated genes were identified between shoot apices containing mostly male flower buds and only female flower buds. Based on gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, the differentially expressed genes were mainly enriched in the ethylene and auxin synthesis and signal transduction pathways. In addition, shoot apices at the 4-leaf stage were treated with the ethylene-releasing agent 2-chloroethylphosphonic acid (Ethrel), aminoethoxyvinyl glycine (AVG), AgNO3 and indoleacetic acid (IAA). The number of female flowers up to node 20 on the main stem of '2013-12' increased significantly after Ethrel and IAA treatment and decreased significantly after AVG and AgNO3 treatment. The female flowers in '9-6' showed slight changes after treatment with the exogenous chemicals. The expression of key genes in ethylene synthesis and signal transduction (CmaACS7, CmaACO1, CmaETR1 and CmaEIN3) was determined using quantitative RT-PCR, and the expression of these four genes was positively correlated with the number of female flowers in '2013-12'. The variations in gene expression, especially that of CmaACS7, after chemical treatment were small in '9-6'. From stage 1 (S1) to stage 7 (S7) of flower development, the expression of CmaACS7 in the stamen was much lower than that in the ovary, stigma and style. These transcriptome data and chemical treatment results indicated that IAA might affect pumpkin sex expression by inducing CmaACS7 expression and indirectly affecting ethylene production, and the ethylene synthesis and signal transduction pathways play crucial roles in pumpkin flower sex expression. A possible reason for the differences in sex expression between pumpkin lines '2013-12' and '9-6' was proposed based on the key gene expression. Overall, these transcriptome data and chemical treatment results suggest important roles for ethylene in pumpkin sex expression.

Dataset Information

Sex-Dependent Variation of Pumpkin (Cucurbita maxima cv. Big Max) Nectar and Nectaries as Determined by Proteomics and Metabolomics.

Publications

Sex-Dependent Variation of Pumpkin (<i>Cucurbita maxima</i> cv. Big Max) Nectar and Nectaries as Determined by Proteomics and Metabolomics.

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