The role of alanine synthesis and nitrate‐induced nitric oxide production during hypoxia stress in Cucurbita pepo nectaries
Autor: | Rodney T. Venterea, Clay J. Carter, Rahul Roy, Erik M. Solhaug |
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Rok vydání: | 2020 |
Předmět: |
0106 biological sciences
0301 basic medicine Plant Nectar Nitrogen Flowers Plant Science Nitric Oxide Nitrate reductase Nitrate Reductase 01 natural sciences 03 medical and health sciences Cucurbita pepo chemistry.chemical_compound Cucurbita Nitrate Gene Expression Regulation Plant Stress Physiological Genetics Nectar Amino Acids Hypoxia Plant Proteins Alanine chemistry.chemical_classification Nitrates biology food and beverages Alanine Transaminase Nectar secretion Cell Biology Metabolism biology.organism_classification Amino acid 030104 developmental biology Biochemistry chemistry Sugars 010606 plant biology & botany |
Zdroj: | The Plant Journal. 105:580-599 |
ISSN: | 1365-313X 0960-7412 |
Popis: | Floral nectar is a sugary solution produced by nectaries to attract and reward pollinators. Nectar metabolites, such as sugars, are synthesized within the nectary during secretion from both pre-stored and direct phloem-derived precursors. In addition to sugars, nectars contain nitrogenous compounds such as amino acids; however, little is known about the role(s) of nitrogen (N) compounds in nectary function. In this study, we investigated N metabolism in Cucurbita pepo (squash) floral nectaries in order to understand how various N-containing compounds are produced and determine the role of N metabolism in nectar secretion. The expression and activity of key enzymes involved in primary N assimilation, including nitrate reductase (NR) and alanine aminotransferase (AlaAT), were induced during secretion in C. pepo nectaries. Alanine (Ala) accumulated to about 35% of total amino acids in nectaries and nectar during peak secretion; however, alteration of vascular nitrate supply had no impact on Ala accumulation during secretion, suggesting that nectar(y) amino acids are produced by precursors other than nitrate. In addition, nitric oxide (NO) is produced from nitrate and nitrite, at least partially by NR, in nectaries and nectar. Hypoxia-related processes are induced in nectaries during secretion, including lactic acid and ethanolic fermentation. Finally, treatments that alter nitrate supply affect levels of hypoxic metabolites, nectar volume and nectar sugar composition. The induction of N metabolism in C. pepo nectaries thus plays an important role in the synthesis and secretion of nectar sugar. |
Databáze: | OpenAIRE |
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