Functional characterization of a Nudix hydrolase AtNUDX8 upon pathogen attack indicates a positive role in plant immune responses.

Published

Journal Article

Nudix hydrolases comprise a large gene family of twenty nine members in Arabidopsis, each containing a conserved motif capable of hydrolyzing specific substrates like ADP-glucose and NADH. Until now only two members of this family, AtNUDX6 and AtNUDX7, have been shown to be involved in plant immunity. RPP4 is a resistance gene from a multigene family that confers resistance to downy mildew. A time course expression profiling after Hyaloperonospora arabidopsidis inoculation in both wild-type (WT) and the rpp4 mutant was carried out to identify differentially expressed genes in RPP4-mediated resistance. AtNUDX8 was one of several differentially expressed, downregulated genes identified. A T-DNA knockout mutant (KO-nudx8) was obtained from a Salk T-DNA insertion collection, which exhibited abolished AtNUDX8 expression. The KO-nudx8 mutant was infected separately from the oomycete pathogen Hpa and the bacterial pathogen Pseudomonas syringae pv. maculicola ES4326. The mutant displayed a significantly enhanced disease susceptibility to both pathogens when compared with the WT control. We observed a small, stunted phenotype for KO-nudx8 mutant plants when grown over a 12/12 hour photoperiod but not over a 16/8 hour photoperiod. AtNUDX8 expression peaked at 8 hours after the lights were turned on and this expression was significantly repressed four-fold by salicylic acid (SA). The expression of three pathogen-responsive thioredoxins (TRX-h2, TRX-h3 and TRX-h5) were downregulated at specific time points in the KO-nudx8 mutant when compared with the WT. Furthermore, KO-nudx8 plants like the npr1 mutant, displayed SA hypersensitivity. Expression of a key SA biosynthetic gene ICS1 was repressed at specific time points in the KO-nudx8 mutant suggesting that AtNUDX8 is involved in SA signaling in plants. Similarly, NPR1 and PR1 transcript levels were also downregulated at specific time points in the KO-nudx8 mutant. This study shows that AtNUDX8 is involved in plant immunity as a positive regulator of defense in Arabidopsis.

Full Text

Duke Authors

Cited Authors

  • Fonseca, JP; Dong, X

Published Date

  • January 2014

Published In

Volume / Issue

  • 9 / 12

Start / End Page

  • e114119 -

PubMed ID

  • 25436909

Pubmed Central ID

  • 25436909

Electronic International Standard Serial Number (EISSN)

  • 1932-6203

International Standard Serial Number (ISSN)

  • 1932-6203

Digital Object Identifier (DOI)

  • 10.1371/journal.pone.0114119

Language

  • eng