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

Roosa Leimu,Lena Kloss,Markus Fischer

doi:10.1371/journal.pone.0042326

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.

Highlights

The rapid changes in environmental conditions due to human activities expose plants to an elevated environmental stress including drought, salinity, extreme temperatures, and altered interactions with herbivores and pathogens
In addition to environmental stress plants can suffer from intrinsic genetic stress, which has been suggested to arise as inbreeding changes the genetic architecture of plants and their populations [1]
Inbreeding effects on CHT activity tended to vary among populations (Table 1)

Summary

Introduction

The rapid changes in environmental conditions due to human activities expose plants to an elevated environmental stress including drought, salinity, extreme temperatures, and altered interactions with herbivores and pathogens. In addition to environmental stress plants can suffer from intrinsic genetic stress, which has been suggested to arise as inbreeding changes the genetic architecture of plants and their populations [1] This genetic stress is becoming increasingly important especially in natural populations where inbreeding is ubiquitous because populations are commonly getting smaller due to human activities [2]. A number of studies have reported effects of plant inbreeding on herbivore resistance and tolerance, plant quality for herbivores, herbivore performance, and pathogen infection rates at phenotypic level [5,6,7,8,9,10,11,12,13] These effects varied from positive to negative, i.e., from inbreeding benefits to inbreeding depression

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Discussion

Conclusion