Ethylene metabolism in Scots pine (Pinus sylvestris) shoots during the year

Abstract

Ethylene evolution, concentrations of 1-aminocyclopropane-1-carboxylic acid (ACC) and ACC conjugates, activities of ACC synthase and ACC oxidase, and cambial growth as measured by tracheid production were monitored from November to July in 1-year-old shoots, and between July and September in current-year shoots, of Scots pine (Pinus sylvestris L.). Needles, buds and four stem parts (cortex, phloem, cambial region and mature xylem) were surveyed. Ethylene evolution was quantified by gas chromatography. Free ACC and bound ACC (after acidic hydrolysis of ACC conjugates) were quantified by combined gas chromatography-mass spectrometry, with [2H]ACC as an internal standard. Activities of ACC synthase and ACC oxidase were measured in crude protein extracts. We detected high activities of ACC synthase in needles and buds, but not in stem fractions except the phloem. In July, during the period of intensive shoot growth, we found ACC only in buds and needles. In contrast, ACC oxidase activity was high in stem tissues, particularly in the cambial region during the period of rapid tracheid production, but no ACC oxidase activity was detected in needles and buds. Nevertheless, needles evolved large amounts of ethylene. Ethylene was produced by all stem fractions, and the peak rate of ethylene evolution in the cambial region coincided with the period of maximal tracheid production. Conjugated ACC was present in every fraction except mature xylem. The concentration of conjugated ACC decreased when rates of tracheid production and ethylene evolution were high, suggesting that conjugated ACC may serve as a source for ACC in the cambial region. The regulation of ethylene biosynthesis in Scots pine shoots is discussed.

Enhanced growth and ethylene increases spiral grain formation in Picea abies and Abies balsamea trees

“…3). This is in agreement with a number of studies in Norway spruce (Eklund 1990;Eklund et al 1992) and Scots pine (Ingemarsson et al 1991;Klintborg et al 2002) where it was shown that ethylene evolution is correlated to the period of most intense growth. Ethrel treatment of stem cambium in Picea abies (Eklund and Tiltu 1999) and Abies balsamea Little 1998, 2000) and ethylene gas treatment of cambium of Picea abies (Eklund and Tiltu 1999), Pinus taeda (Telewski 1990), and other pine species (Neel and Harris 1971) has also been shown to increase tracheid production.…”

Ethylene in induced conifer defense: cDNA cloning, protein expression, and cellular and subcellular localization of 1-aminocyclopropane-1-carboxylate oxidase in resin duct and phenolic parenchyma cells

“…In conifers, several endogenous roles have been established for the phytohormone ethylene. Ethylene has been correlated with cambial zone activity leading to xylem (wood) formation and diVerentiation (Ingemarsson et al 1991;Eklund and Little 1998;Little and Eklund 1999;Klintborg et al 2002). Previous studies have established a strong correlation between wounding, endogenous ethylene, and resin accumulation in conifers (Popp et al 1995;.…”

“…In addition, exogenous ethylene application can increase resin production and the number of resin ducts in several conifer species (Telewski et al 1983;Yamamoto and Kozlowski 1987;Katoh and Croteau 1997;. ACO activity, the Wnal step in ethylene formation, has previously been detected in several conifer species (Plomion et al 2000;Reynolds and John 2000;Klintborg et al 2002), but little is known about the corresponding ACO genes, their expression and cellular localization in conifers and the relationship of ACO with ethylene production and activities of specialized cells for phenolic or terpenoid formation after wounding in stems.…”

Characterization and developmental expression of a glutamate decarboxylase from maritime pine

“…4e), suggesting that GAD activity is the major regulator of hypocotyl GABA levels during seedling development. To further characterize GAD in pine, we compared GAD expression with the expression of other genes encoding enzymes associated with seedling diVerentiation, including cytosolic NADP + -IDH (Palomo et al 1998;Pascual et al 2008), ascorbate peroxidase (APX), and oxidase (AOX) (Pignocchi and Foyer 2003;de Pinto and De Gara 2004), enzymes linked with ligniWcation and signaling, including laccase (LAC, Gavnholt and Larsen 2002), and 1-aminocyclopropane-1-carboxylic acid synthase (ACS), and oxidase (ACO), enzymes involved in ethylene synthesis that has been described to be connected to ligniWcation of plant stem (Klintborg et al 2002). Northern blots hybridized with speciWc probes indicated that these genes were diVerentially expressed in organs of pine seedlings (Fig.…”