DNA Damage responses in plant stem cells

Plants are sessile organisms that cannot escape environmental hazards, which induce DNA damage and cause mutations. Plants are also subject to DNA damage caused by endogenous processes such as transposon movement. Plant stem cell populations in particular must be protected from genotoxicity, as they are the origin of all organs, together with the germline. In accordance with this premise, plant stem cells were found to be hypersensitive to Double Strand Breaks (DSBs), leading to their specific killing via the ATAXIA TELANGIECTASIA MUTATED (ATM) and SUPPRESSOR OF GAMMA RESPONSE 1 (SOG1) genes. However, the components of the pathway leading to programmed cell death (PCD) in response to DSBs in plant stem cells are still unknown, and the in vivo DNA damaging agents relevant to this mechanism have not been characterised, providing the starting point of this thesis. Here, a candidate gene approach and a forward genetics screen in the root stem cells did not yield new factors of the pathway leading to PCD in root stem cells. However, a specific ecotype showed an absence of DSBs-induced PCD, revealing natural variation in stem cell responses to DSBs. In relation to responses to endogenous DNA damage in plant stem cells, I identified several chromatin‐silencing mutants showing spontaneous PCD in the root meristem, and studied the link between transposon silencing and the ATM/SOG1 pathway. Finally, by characterising responses to Cre‐catalysed recombination in the shoot meristem, I uncovered an unexpected link between the DNA damage response pathway and chromatin silencing, This silencing was dependent on ATM/SOG1, linked to the production of 24-nt siRNA, and required the RNA polymerase IV and ARGONAUTE 6. My work links DNA damage responses to chromatin silencing in Arabidopsis stem cells.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2014

Author dc:creator

• Haleux, Pauline

Language dc:language

en