Inbreeding Alters Activities of the Stress-Related Enzymes Chitinases and β-1,3-Glucanases

Abstract

Pathogenesis-related proteins, chitinases (CHT) and β-1,3-glucanases (GLU), are stress proteins up-regulated as response to extrinsic environmental stress in plants. It is unknown whether these PR proteins are also influenced by inbreeding, which has been suggested to constitute intrinsic genetic stress, and which is also known to affect the ability of plants to cope with environmental stress. We investigated activities of CHT and GLU in response to inbreeding in plants from 13 Ragged Robin (Lychnis flos-cuculi) populations. We also studied whether activities of these enzymes were associated with levels of herbivore damage and pathogen infection in the populations from which the plants originated. We found an increase in pathogenesis-related protein activity in inbred plants from five out of the 13 investigated populations, which suggests that these proteins may play a role in how plants respond to intrinsic genetic stress brought about by inbreeding in some populations depending on the allele frequencies of loci affecting the expression of CHT and the past levels of inbreeding. More importantly, we found that CHT activities were higher in plants from populations with higher levels of herbivore or pathogen damage, but inbreeding reduced CHT activity in these populations disrupting the increased activities of this resistance-related enzyme in populations where high resistance is beneficial. These results provide novel information on the effects of plant inbreeding on plant–enemy interactions on a biochemical level.

The effects of stress intensity and stress type on inbreeding depression inSilene vulgaris

“…It has been shown that at the cellular level, both inbreeding and environmental stress can lead to similar molecular responses, which could result in an increase of ID with stress intensity (Leimu et al. ; Reed et al. ).…”

Plant mating systems affect adaptive plasticity in response to herbivory

“…These studies indicate that inbreeding may be a significant factor in expression of resistance, although the magnitude of this effect probably depends on the population mating system history, and the opportunity for selective purging of load associated with defence genes. A previous study showed that inbreeding reduced the production of defence‐related secondary metabolites (Campbell et al ., ), complementing work showing reduced volatile emissions and trichome production (Kariyat et al ., , ), and reduced pathogenesis‐related protein expression (Leimu et al ., ) in inbred plants. Campbell et al .…”

“…Inbreeding can also influence fundamental aspects of a species' ecology, such as tolerance of abiotic stress (Hauser and Loeschcke, 1996;Kristensen et al, 2008), and interactions with competitors (Darwin, 1876;Schmitt and Ehrhardt, 1990) or natural enemies (Steets et al, 2007). These effects presumably arise from deleterious mutations (genetic load) at loci underlying ecologically relevant traits, although evidence for such mechanisms is sparse (Leimu et al, 2012a;. In turn, when ecological interactions alter the magnitude of inbreeding depression (Cheptou and Donohue, 2011;, they may impose natural selection on mating strategies by making the benefits of outcrossing dependent on specific aspects of the environment (e.g.…”

Transgenerational impacts of herbivory and inbreeding on reproductive output in Solanum carolinense

“…Consequently, inbred progeny often exhibit inbreeding depression such as reduced germination and growth, slower development, and decreased reproductive output relative to outbred plants (e.g., Husband and Schemske, 1996;Baskin and Baskin, 2015). Inbred plants also typically show reduced expression of constitutive and induced defense-related traits (Kariyat et al, 2012(Kariyat et al, , 2013Leimu et al, 2012;Campbell et al, 2014), which can result in reduced resistance to herbivores (Carr and Eubanks, 2002;Ivey et al, 2003;Leimu et al, 2008;Delphia et al, 2009; Bello-Bedoy and Núñez-Farfán, 2010; Kariyat et al, 2011). Furthermore, the magnitude of inbreeding depression is environmentally dependent, and its consequences have been shown to be more severe when plants are exposed to environmental stress, including herbivory (e.g., Armbruster and Reed, 2005;Hayes et al, 2005).…”