Page 116 - PC2019 Program & Proceedings

PLANT CANADA 2019

S17. Multigenerational heat stress induces phenotypic resilience as well as genetic and epigenetic
variations in Arabidopsis thaliana offspring
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Yadav, N. ; V. Titov; I. Ayemere; B. Byeon; Y. Ilnytskyy; I. Kovalchuk
The University of Lethbridge
The stress memory of plants has become a recent topic of interest as unpredictable weather patterns and
widespread environmental changes through global warming are now quite commonplace. To that end, the
current study intended to explore the effects of multigenerational heat stress memory in
Arabidopsis thaliana. The 25 generations of Arabidopsis propagated in the presence of heat stress. The
single (F1_H) and multigenerational (F25_H) stressed-progenies showed higher tolerance as compared to
their parallel control. Both stressed-progenies also showed elevated homologous recombination frequency
(HRF). Methylome analysis revealed that F25_H was different from parallel and parental control
progenies by more than 66,000 cytosine methylations. Hierarchical clustering of these epimutations
separated stressed- and parental-progenies plants into distinct groups suggesting directional changes.
Genome analysis deciphered that F25_H showed 3-times more genetic variants (SNPs and INDELs) than
control-progenies. Comparative analysis revealed that epigenetic-variations are more spontaneous and
prevalent than genetic-variations. Further Gene Ontology analysis revealed that SNPs were enriched
mostly at unknown biological processes in all lineages although processes such as response to stress and
stimulus were enriched more in stressed-progenies. The DMRs (differentially methylated regions) were
enriched mostly in processes such as transcription and DNA dependent processes, DNA or RNA
metabolism. Overall our study highlighted the existence of multigenerational heat stress-induced genetic
and epigenetic variations and the adaptability of genome and epigenome in plant phenotypic resilience to
heat stress.

Narendra Yadav (narendra.yadav@uleth.ca)

S18. Root damage and immune responses at cellular resolution
Geldner, N.
University of Lausanne

Microbe-associated molecular pattern (MAMP) recognition is crucial to the plant’s immune system, but
how this sophisticated perception system can be usefully deployed in roots, continuously exposed to
bacteria, remains unresolved. We have analyzed MAMP receptor expression and responses at cellular
resolution in Arabidopsis and found that differentiated outer layers, exposed to bacteria, show low
receptor levels and lack MAMP responsiveness. However, these cells can be locally “gated” to become
responsive, by either neighbor cell damage or emerging lateral roots. Laser-induced localized damage
also leads to immune responses to an otherwise non-immunogenic, beneficial bacterium and enhances
responses to a root pathogenic bacterium. We find that single cell damage in differentiated roots leads to
regional ROS and calcium waves, ethylene responses, but no detectable jasmonate responses. Treatment
with DAMPs alone do not re-iterate laser-induced damage and, surprisingly, the highly local upregulation
of MAMP responses by damage is independent of ethylene signalling. Our findings demonstrate that
spatially restricted receptor expression is crucial for an appropriate MAMP response in roots and helps to
conceptualize how MAMP perception can be used despite a continuous presence of microbial patterns in
the soil.

Niko Geldner (Niko.Geldner@unil.ch)

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