Role of photosynthesis and analysis of key enzymes involved in primary metabolism throughout the lifespan of the tobacco flower

Abstract

Although the physiological and economical relevance of flowers is recognized, their primary metabolism during development has not been characterized, especially combining protein, transcript, and activity levels of the different enzymes involved. In this work, the functional characterization of the photosynthetic apparatus, pigment profiles, and the main primary metabolic pathways were analysed in tobacco sepals and petals at different developmental stages. The results indicate that the corolla photosynthetic apparatus is functional and capable of fixing CO(2); with its photosynthetic activity mainly involved in pigment biosynthesis. The particular pattern of expression, across the tobacco flower lifespan, of several proteins involved in respiration and primary metabolism, indicate that petal carbon metabolism is highest at the anthesis stage; while some enzymes are activated at the later stages, along with senescence. The first signs of corolla senescence in attached flowers are observed after anthesis; however, molecular data suggest that senescence is already onset at this stage. Feeding experiments to detached flowers at anthesis indicate that sugars, but not photosynthetic activity of the corolla, are capable of delaying the senescence process. On the other hand, photosynthetic activity and CO(2) fixation is active in sepals, where high expression levels of particular enzymes were detected. Sepals remained green and did not show signs of senescence in all the flower developmental stages analysed. Overall, the data presented contribute to an understanding of the metabolic processes operating during tobacco flower development, and identify key enzymes involved in the different stages.

Jasmonoyl-l-Isoleucine Coordinates Metabolic Networks Required for Anthesis and Floral Attractant Emission in Wild Tobacco (Nicotiana attenuata)

“…However, Müller et al (2010) demonstrated that fundamental changes in floral primary metabolism can function in roles beyond osmotic regulation, and recent studies demonstrated signaling activity for sugars in plant development (Cho et al, 2006;Seo et al, 2011;Yang et al, 2013;Yu et al, 2013). We notably observed a correlation between the MeJA/COR-responsive increase in CHAL1 transcripts and sugar levels in ir-aoc corollas, a pattern consistent with the previously reported sugar-dependent expression of CHAL in petunia (Tsukaya et al, 1991;Weiss et al, 1992;Moalem-Beno et al, 1997).…”

“…For instance, the rapid expansion of petal tissues is paralleled by a rapid increase in soluble sugar levels in many plant species (Evans and Reid, 1988;Bieleski, 1993;Vergauwen et al, 2000;Müller et al, 2010). The role played by carbohydrate metabolism in the coordination of developmental transitions and flowering time has recently received more attention (Cho et al, 2006;Wahl et al, 2013;Yang et al, 2013).…”

“…The role played by carbohydrate metabolism in the coordination of developmental transitions and flowering time has recently received more attention (Cho et al, 2006;Wahl et al, 2013;Yang et al, 2013). Sugar and energy metabolism are thereby of central importance for the petals' osmotic pressure and energy-demanding processes that are required for anthesis and the expression of floral metabolic traits (Bieleski, 1993;Kuipef et al, 1995;Müller et al, 2010). While cross-regulation between carbohydrates and gibberellins during flower development has been established (Moalem-Beno et al, 1997), little is known about possible connections between floral carbohydrate metabolism and JA signaling, since most studies on JAs signaling metabolic output have been restricted to plant leaves and roots (Babst et al, 2005;Tejeda-Sartorius et al, 2008).…”

Ascorbate metabolism in vegetative and reproductive organs of "cherry" tomato

“…Indeed, our results showed high transcript accumulation levels for most studied genes comparable or, in some cases, even higher than leaves (Figs 3 and 4). The fact that in flowers both photosynthesis and cell division and extension take place possibly explains this finding (Muller et al 2010). To better understand AsA metabolism in fruits, red ripe cherry tomato fruits were divided in two parts, pericarp and pulp (containing seeds, locular parenchyma and placenta).…”

Floral Metabolism of Sugars and Amino Acids: Implications for Pollinators’ Preferences and Seed and Fruit Set

“…As photosynthesis in flowers is confined to sepals and young petals, floral tissues rely heavily on the source-to-sink flow for the supply of carbon resources (Müller et al, 2010). Experiments performed in the early 1970s with cut carnation (Dianthus caryophyllus) flowers revealed that Suc is the sugar preferentially transported alongside the flower peduncle across the phloem (Ho and Nichols, 1975).…”