Higher plant terpenoids: A phytocentric overview of their ecological roles

Abstract

Characteristics of higher plant terpenoids that result in mediation of numerous kinds of ecological interactions are discussed as a framework for this Symposium on Chemical Ecology of Terpenoids. However, the role of terpenoid mixtures, either constitutive or induced, their intraspecific qualitative and quantitative compositional variation, and their dosage-dependent effects are emphasized in subsequent discussions. It is suggested that little previous attention to these characteristics may have contributed to terpenoids having been misrepresented in some chemical defense theories. Selected phytocentric examples of terpenoid interactions are presented: (1) defense against generalist and specialist insect and mammalian herbivores, (2) defense against insect-vectored fungi and potentially pathogenic endophytic fungi, (3) attraction of entomophages and pollinators, (4) allelopathic effects that inhibit seed germination and soil bacteria, and (5) interaction with reactive troposphere gases. The results are integrated by discussing how these terpenoids may be contributing factors in determining some properties of terrestrial plant communities and ecosystems. A terrestrial phytocentric approach is necessitated due to the magnitude and scope of terpenoid interactions. This presentation has a more broadly based ecological perspective than the several excellent recent reviews of the ecological chemistry of terpenoids.

Essential oils and their components as an alternative in the control of mosquito vectors of disease

“…Como ya se mencionó, los aceites esenciales pueden ser una fuente alternativa de agentes de control de mosquitos y otros insectos, ya que son ricos en compuestos con actividad biológica, son biodegradables y se transforman en productos no tóxicos, son amigables con el medio ambiente y están potencialmente adecuados para su uso en los programas de control integral (21,30,31). De hecho, muchos investigadores han informado sobre la eficacia de los aceites esenciales como agentes contra larvas y ejemplares adultos y, asimismo, como repelentes (14,23,(30)(31)(32).…”

“…El carácter lipófilo de los aceites y sus componentes también tiene un rol clave. Se ha observado que la lipofilia está muy relacionada con la inhibición y la desactivación enzimática (21). La importancia de la lipofilia de los terpenos y terpenoides se ha confirmado al estudiar la relación entre propiedad y actividad, en los cuales el perfil hidrofóbico se ha relacionado estrechamente con la actividad larvicida (119).…”

“…Las plantas han aprovechado a los insectos como agentes polinizadores, pero también han tenido que desarrollar mecanismos de defensa contra insectos depredadores (21). En este contexto, los aceites esenciales y sus componentes se destacan como compuestos potencialmente útiles contra los insectos (22,23).…”

Terpene production in the peel of sweet orange fruits

“…Transcripts for terpene synthases were detected in fruit, leaf, flower, and bark tissues, which probably reflects the general role of terpenes as pollinator attracters or repellents against herbivores or pathogens (Langenheim, 1994;Bouwmeester et al, 1999;Dicke, 1999;Pichersky and Gershenzon, 2002;Dudareva et al, 2003). We focused our analysis on the terpene synthases that were identified in the epicarp of sweet orange fruits since citrus essential oil is extracted from the flavedo where they accumulate in specialized secretion cavities (Lucker et al, 2002).…”

“…The natural products can be divided into three different groups: alkaloids, phenylpropanoids and phenolic compounds, and terpenoids, which constitute the largest and the most diverse class. The vast majority of the terpenoids are classified as secondary metabolites whose functions can be ecological, providing defense against herbivores or pathogens, attracting animals that disperse pollen and seeds, or inhibiting germination of neighbor plants (Langenheim, 1994;Bouwmeester et al, 1999;Dicke, 1999;Pichersky and Gershenzon, 2002). The biosynthesis of terpenes is divided into four steps: synthesis of the precursors, isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) through two different pathways; repetitive addition of the precursors to form a series of homologues of prenyl diphosphate, which are the immediate precursors of the different classes of terpenes; elaboration of the terpenes backbones by the activity of specific synthases; and secondary enzymatic modification of these backbones that will give the functional properties and family diversity.…”