Nuclear components and dynamics during plant innate immunity

Abstract

In plants, efficient immune responses against microbial infection depend on the ability to rapidly couple pathogen recognition to downstream signaling responses. In this context, plant immunity requires highly dynamic responses that involve multiple organelles during the recognition and signaling events associated with defense. Nuclear dynamics play a critical role in plant immunity based on the growing number of reports revealing that nuclear localization of pathogen effectors, plant disease resistance proteins, and key plant components, including transcription factors and regulators, are essential for immunity. This Research Topic provides an overview of the current knowledge about the importance of nuclear components-both from the "microbial side" and from the "plant side"-and nuclear dynamics during the establishment of plant immune responses.Mutations in plant cellular factors involved in the transport of macromolecules through the nuclear envelope compromise plant resistance signaling, underlining the importance of nucleocytoplasmic trafficking during plant innate immunity. The Mini-Review article by Gaouar and Germain (2013) describes the importance of nuclear mRNA export during plant immune responses whereas Wirthmueller et al. (2013) discuss importin-α-mediated nuclear translocation and how microbial effectors may compete with host cargo proteins for nuclear uptake.Following their delivery into plant cells, a significant number of effector proteins from different pathogenic microorganisms, including viruses, oomycetes, fungi, nematodes, and bacteria, are targeted to the nucleus by co-opting the host nuclear import machinery. This suggests that effectors may manipulate host transcription or directly target essential host nuclear components for the benefit of the pathogen. Indeed, pathogen-induced transcriptional regulation in host cells plays a crucial role in the establishment of plant defense and associated plant cell death responses. Several articles in this Research Topic highlight these ideas. Quentin et al. (2013) describe effectors from plant parasitic nematodes that target host nuclei and possibly interact with nuclear proteins to establish feeding cells in infected plants. In their Original Research article, Ma et al. (2013) show that nuclear localization of the Avr2 effector from the xylem-colonizing fungus Fusarium oxysporum is required to trigger I2-mediated resistance in tomato plants, whereas Stam et al. (2013) show the diversity of nuclear functions of CRN effectors from the oomycete Phytophthora infestans. Finally, the Opinion article by Noël et al. (2013) discusses recent advances in predicting target sequences of nuclear-targeted TAL effectors from the plant pathogenic bacteria of the genus Xanthomonas.It has been estimated that about 25% of Arabidopsis genes are transcriptionally regulated in response to pathogen infection and a significant number of transcription factors are involved in the defense gene regulation. Raffaele and Rivas (2013) review our current knowledge of the transcri...

A Receptor Pair with an Integrated Decoy Converts Pathogen Disabling of Transcription Factors to Immunity

“…PopP2 Uses Nε-Acetylation to Alter Eukaryotic TF-DNA Binding Reprogramming of gene transcription is necessary for mobilizing host defenses, and many bacterial effectors modulate transcription (Rivas and Deslandes, 2013). Bacterial strategies include the inhibition of RNA-binding proteins that enhance expression of immunity-related RNAs (Nicaise et al, 2013) and direct transcriptional activation of host genes benefiting pathogen growth and dissemination (Boch et al, 2009).…”

Molecular analysis of importin-α-mediated nucleocytoplasmic signaling in plant innate immunity

“…Interaction of effectors with host proteins can take place at various locations including the host cell cytoplasm (Figure 1.1 (2). However, several effector proteins are targeted to host cell nuclei (Caillaud et al, 2012a;Caillaud et al, 2012b;Rivas and Deslandes, 2013;Deslandes et al, 2003;Schornack et al, 2010). The presence of predicted NLS motifs in some of these effectors indicate that the host cells' nuclear import machinery is exploited for nuclear translocation (Chisholm et al, 2006;Schornack et al, 2010;Boch and Bonas, 2010).…”