title: Extracellular invertase LIN6 of tomato: a pivotal enzyme for integration of metabolic, hormonal, and stress signals is regulated by a diurnal rhythm.
abstract: To elucidate the regulation pattern of extracellular invertase LIN6 of tomato, the corresponding promoter has been cloned and the sink-tissue specific expression and its regulation by sugars, stress stimuli, growth regulators, and the diurnal rhythm is shown. The in situ analysis of transgenic tobacco plants expressing a LIN6 promoter::beta-glucuronidase reporter gene fusion demonstrates LIN6 expression in sink tissues, such as pollen grains and vascular tissues of leaves and stems. LIN6 is up-regulated in close proximity to wounded tissue, and by methyl jasmonate and abscisic acid, global signals known to modulate defence/stress response. Salicylic acid on the other hand, as well as acetyl salicylic acid, suppresses LIN6 expression, supporting the fact that LIN6 is an inducible compound of the defence/stress response pathway that is antagonistically regulated by jasmonates and salicylates. Induction of the LIN6 promoter in stable transformed BY2 suspension cultures by sucrose and the growth-promoting phytohormones cytokinin and auxin along histochemical expression data, showing LIN6 expression in germinating seeds and seedlings, indicates a role of LIN6 invertase during growth processes. In addition, LIN6 is regulated by a diurnal rhythm that drives LIN6 expression in subjective dawn. Transactivation assays with circadian oscillator elements of Arabidopsis Circadian Clock Associated 1 and Late Elongated Hypocotyl demonstrate functional interaction with the LIN6 promoter.
authors.affiliation: Lehrstuhl für pharmazeutische Biologie, Universität Würzburg, Würzburg, Germany.
authors.forename: Reinhard K
authors.initials: RK
authors.lastname: Proels
authors.forename: Thomas
authors.initials: T
authors.lastname: Roitsch
mesh_terms: D002940:Circadian Rhythm; D003583:Cytokinins / Q000378:metabolism; D005110:Extracellular Space / Q000201:enzymology*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism; D018551:Solanum lycopersicum / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D010937:Plant Growth Regulators / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D020156:Salicylic Acid / Q000378:metabolism; D013312:Stress, Physiological; D043324:beta-Fructofuranosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D003583:Cytokinins; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D010940:Plant Proteins; D043324:beta-Fructofuranosidase; D020156:Salicylic Acid