Abstract
Pharmacological inhibition of poly(ADP-ribose) polymerase (PARP) or loss of Arabidopsis thaliana PARG1 (poly(ADP-ribose) glycohydrolase) disrupt a subset of plant defenses. In the present study we examined the impact of altered poly(ADP-ribosyl)ation on early gene expression induced by the microbe-associate molecular patterns (MAMPs) flagellin (flg22) and EF-Tu (elf18). Stringent statistical analyses and filtering identified 178 genes having MAMP-induced mRNA abundance patterns that were altered by either PARP inhibitor 3-aminobenzamide (3AB) or PARG1 knockout. From the identified set of 178 genes, over fifty Arabidopsis T-DNA insertion lines were chosen and screened for altered basal defense responses. Subtle alterations in callose deposition and/or seedling growth in response to those MAMPs were observed in knockouts of At3g55630 (FPGS3, a cytosolic folylpolyglutamate synthetase), At5g15660 (containing an F-box domain), At1g47370 (a TIR-X (Toll-Interleukin Receptor domain)), and At5g64060 (a predicted pectin methylesterase inhibitor). Over-represented GO terms for the gene expression study included "innate immune response" for elf18/parg1, highlighting a subset of elf18-activated defense-associated genes whose expression is altered in parg1 plants. The study also allowed a tightly controlled comparison of early mRNA abundance responses to flg22 and elf18 in wild-type Arabidopsis, which revealed many differences. The PARP inhibitor 3-methoxybenzamide (3MB) was also used in the gene expression profiling, but pleiotropic impacts of this inhibitor were observed. This transcriptomics study revealed targets for further dissection of MAMP-induced plant immune responses, impacts of PARP inhibitors, and the molecular mechanisms by which poly(ADP-ribosyl)ation regulates plant responses to MAMPs.
Highlights
The plant immune system is composed of at least three basic components: pre-formed defenses, infection-induced basal defenses, and R-gene mediated defenses [1,2,3]
We report here a genome-wide gene expression analysis of the effects of poly(ADP-ribose) polymerase (PARP) inhibitor and, separately, parg1 knockout, on early microbe-associate molecular patterns (MAMPs)-induced gene expression in the plant basal defense response
We studied Arabidopsis thaliana wild-type (Col-0), 3AB-treated and parg1-2 T-DNA knockout plants responding to the MAMP elicitors flg22 or elf18
Summary
The plant immune system is composed of at least three basic components: pre-formed defenses, infection-induced basal defenses, and R-gene mediated defenses [1,2,3]. Once preformed structural barriers are breached, the basal immune response is activated by pattern. Service Award from the National Institutes of Health The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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