Molecular dissection of protein poly(ADP-ribosyl)ation in plant immunity and pathogen-induced DNA damage

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Immune responses in plants is collectively represented by a wide range of processes that have evolved to protect plants during pathogen and pest infection. Among the various responses plants use to defend themselves, and moreover, processes that pathogens target to disable the plant immune system, damage to DNA – the genetic code that underpins all of life – is one key point of interaction between plants and pathogens. In the current study, the investigators ask: How do plants protect and repair damage to DNA during pathogen infection to ensure that the immune system continues to function. Previous research in this area suggests that at least 1 type of repair mechanism – poly(ADP-ribosyl)ation (i.e., PARylation) – plays a critical role in a maintenance of cell survival and immune signaling. In short, this mechanism has the ability to detect and repair damage to the plant (host) DNA. As a key process required for immunity during pathogen infection, the researchers will test the hypothesis that PARylation provides a mechanistic link between plant immunity and pathogen-induced DNA damage. The molecular and biochemical mechanisms underlying the regulation of plant immunity by protein PARylation and genome integrity after pathogen infection will be determined. Knowledge generated from these studies is expected to help design better disease control strategies for crop improvement.PARylation is primarily mediated by poly(ADP-ribose) polymerase (PARP), which transfers ADP-ribose moieties from NAD+ to acceptor proteins. This modification is reversible and the covalently attached poly(ADP-ribose) can be cleaved from acceptor proteins by poly(ADP-ribose) glycohydrolase (PARG). PARylation has been extensively characterized in humans due to its profound medical impacts in various inflammatory and malignant disorders and especially cancer chemotherapy. However, the function of PARylation in plants is poorly understood. The viability and normal growth of Arabidopsis parp and parg null mutants provide a unique opportunity to study protein PARylation in diverse cellular processes, including plant immunity and DNA damage repair at the whole organismal level. The results of the work will provide novel insights in understanding how the two fundamental surveillance mechanisms, DNA damage and plant defense responses, are intricately interconnected and function coordinately. This proposal aims to unravel the regulatory mechanisms of PARylation in plant immunity, identify the targets of PARylation-regulated immune genes and proteins, and elucidate the mechanism of pathogen-induced DNA damage and how it is protected by PARylation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.