Volatile-Mediated Induced and Passively Acquired Resistance in Sagebrush (Artemisia tridentata)

Abstract

Plants produce a diversity of secondary metabolites including volatile organic compounds. Some species show discrete variation in these volatile compounds such that individuals within a population can be grouped into distinct chemotypes. A few studies reported that volatile-mediated induced resistance is more effective between plants belonging to the same chemotype and that chemotypes are heritable. The authors concluded that the ability of plants to differentially respond to cues from related individuals that share the same chemotype is a form of kin recognition. These studies assumed plants were actively responding but did not test the mechanism of resistance. A similar result was possible through the passive adsorption and reemission of repellent or toxic VOCs by plants exposed to damage-induced plant volatiles (DIPVs). Here we conducted exposure experiments with five chemotypes of sagebrush in growth chambers; undamaged receiver plants were exposed to either filtered air or DIPVs from mechanically wounded branches. Receiver plants exposed to DIPVs experienced less herbivore damage, which was correlated with increased expression of genes involved in plant defense as well as increased emission of repellent VOCs. Plants belonging to two of the five chemotypes exhibited stronger resistance when exposed to DIPVs from plants of the same chemotypes compared to when DIPVs were from plants of a different chemotype. Moreover, some plants passively absorbed DIPVs and reemitted them, potentially conferring associational resistance. These findings support previous work demonstrating that sagebrush plants actively responded to alarm cues and that the strength of their response was dependent on the chemotypes of the plants involved. This study provides further support for kin recognition in plants but also identified volatile-mediated associational resistance as a passively acquired additional defense mechanism in sagebrush.

Induction by caterpillars of stored and emitted volatiles in terpene chemotypes from populations of wild cotton (Gossypium hirsutum)

“…Volatile plant metabolites can function as toxins, repel insect feeding and oviposition, and attract natural enemies of their attackers (Unsicker et al, 2009; Turlings and Erb, 2018). Volatiles also mediate signaling within plants (Rodriguez-Saona and Frost, 2010) and may be passively used as protection, or actively perceived by neighboring plants (Karban et al, 2014b; Erb et al, 2015; Grof-Tisza et al, 2022). Unharmed plants can produce and emit certain volatiles constitutively, a phenomenon particularly prevalent in plant species that accumulate volatile terpenes in specialized structures.…”

“…Keefover-Ring et al, 2009; Taft et al, 2015; Clancy et al, 2016; Bustos-Segura et al, 2017; Grof-Tisza et al, 2021). Importantly, this variation has been associated with differences in resistance to abiotic stress (Amiot et al, 2005; Kleine and Müller, 2014), allelopathy (Linhart et al, 2015), defense against pathogens (Bustos-Segura et al, 2015) and herbivores (Linhart and Thompson, 1999; Kleine and Müller, 2011; Bustos-Segura et al, 2015; Karban et al, 2016; Senft et al, 2019), as well as airborne signaling between plants when stored terpenes are released by damage (Karban et al, 2014a; Grof-Tisza et al, 2022). This variation is likely linked to genetic polymorphisms of the synthetizing enzymes: for instance, variability in a terpene synthase (TPS) gene cluster underlies the constitutive chemotypes of Melaleuca alternifolia (Voelker et al, 2023).…”

Geographic distribution of terpenoid chemotypes inTanacetum vulgaremediates tansy aphid occurrence and abundance

“…For instance, the abundance of pyrrolizidine alkaloids in Senecio jacobaea (Macel & Klinkhamer, 2010) and the abundance of specific monoterpenoids in Pinus banksiana (Taft et al, 2015), Melaleuca alternifolia (Bustos-Segura et al, 2017) and Gossypium hirsutum (Clancy et al, 2023) have been used for the classification of chemotypes. These primary and specialized metabolites in plants have many ecological functions and can strongly influence ecological interactions such as the attraction of herbivore predators, pollinators, and mycorrhizal fungi, defence against herbivores and pathogens, communication with other plants, and protection against UV-B radiation and drought (Dicke et al, 2009;Dixon & Paiva, 1995;Grof-Tisza et al, 2022;Mofikoya et al, 2019).…”

Experimental Growth Conditions affect Direct and Indirect Defences in two Cotton Species

“…As is the case for direct defence, indirect defence mechanisms within a species can be highly varied, and influenced by a number of factors. For instance, considerable quantitative and qualitative variation is observed in VOC profile emissions among different genotypes of the same species (Loughrin et al 1995 ; Turlings et al 1998 ; Halitschke et al 2000 ; Degen et al 2004 ; Clancy et al 2016 , 2023 ; Bustos-Segura and Foley 2018 ; Grof-Tisza et al 2022 ). Although few studies have investigated the importance of environmental conditions on inducible volatile emissions, the growing conditions should have strong effects (Gouinguené and Turlings 2002 ; Olson et al 2009 ).…”