Abstract
Plant-specific NAC transcription factors (TFs) constitute a large family and play important roles in regulating plant developmental processes and responses to environmental stresses, but only some of them have been investigated for effects on disease reaction in cereal crops. Virus-induced gene silencing (VIGS) is an effective strategy for rapid functional analysis of genes in plant tissues. In this study, TaNAC1, encoding a new member of the NAC1 subgroup, was cloned from bread wheat and characterized. It is a TF localized in the cell nucleus, and contains an activation domain in its C-terminal. TaNAC1 was strongly expressed in wheat roots and was involved in responses to infection by the obligate pathogen Puccinia striiformis f. sp. tritici and defense-related hormone treatments such as salicylic acid (SA), methyl jasmonate, and ethylene. Knockdown of TaNAC1 with barley stripe mosaic virus-induced gene silencing (BSMV-VIGS) enhanced stripe rust resistance. TaNAC1-overexpression in Arabidopsis thaliana plants gave enhanced susceptibility, attenuated systemic-acquired resistance to Pseudomonas syringae DC3000, and promoted lateral root development. Jasmonic acid-signaling pathway genes PDF1.2 and ORA59 were constitutively expressed in transgenic plants. TaNAC1 overexpression suppressed the expression levels of resistance-related genes PR1 and PR2 involved in SA signaling and AtWRKY70, which functions as a connection node between the JA- and SA-signaling pathways. Collectively, TaNAC1 is a novel NAC member of the NAC1 subgroup, negatively regulates plant disease resistance, and may modulate plant JA- and SA-signaling defense cascades.
Highlights
Crop plants provide most of the world’s food intake
To profile the expression patterns of TaNAC1 responding to exogenous plant hormones, 2-week-old seedlings of Yr10∗6/Taichung 29 were treated with 1 mM salicylic acid (SA), 0.1 mM MeJA and ET released from 0.2 mM ethephon, respectively (Zhang et al, 2004), and leaf samples were collected at 0, 1, 3, 6, 12, 24 h post-treatment
SEQUENCE ANALYSIS OF PUTATIVE TaNAC1 Based on the EST sequence of a differentially expressed NAC1 gene during stripe rust infection, the corresponding full length gene was cloned from a cDNA library of wheat near-isogenic line (NIL) Yr10∗6/Taichung 29 by PCR with FastPfu DNA Polymerase
Summary
Crop plants provide most of the world’s food intake. A plethora of pathogens including viruses, bacteria, fungi, oomycetes, and nematodes cause severe yield losses in crop production. Multiple defense mechanisms, including basal resistance, PAMP-triggered immunity (PTI) and effector-triggered immunity (ETI), are activated at different stages of pathogen infection. Plant defense systems translate pathogen-induced early signaling events into activation of effective defense responses, most of which depend on the action of plant phytohormones such as salicylic acid (SA), jasmonates (JAs), ethylene (ET), abscisic acid (ABA), auxins, cytokinins (CKs), and gibberellins (GAs; Pieterse et al, 2012). The actions of JAs and SA as signals in the regulation of plant immune responses are well established. The JA and SA defense pathways generally antagonize each other; elevated resistance against necrotrophs is often correlated with increased susceptibility to biotrophs (Glazebrook, 2005; Derksen et al, 2013; Vos et al, 2013)
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