Abstract
Stripe rust is one of the most devastating diseases in wheat. Nucleotide-binding site (NBS) and leucine-rich repeat (LRR) domain receptors (NLRs) recognize pathogenic effectors and trigger plant immunity. We previously identified a unique NLR protein YrU1 in the diploid wheat Triticum urartu, which contains an N-terminal ANK domain and a C-terminal WRKY domain and confers disease resistance to stripe rust fungus Puccinia striiformis f. sp. Tritici (Pst). However, how YrU1 functions in disease resistance is not clear. In this study, through the RNA-seq analysis, we found that the expression of a NAC member TuNAC69 was significantly up-regulated after inoculation with Pst in the presence of YrU1. TuNAC69 was mainly localized in the nucleus and showed transcriptional activation in yeast. Knockdown TuNAC69 in diploid wheat Triticum urartu PI428309 that contains YrU1 by virus-induced gene silencing reduced the resistance to stripe rust. In addition, overexpression of TuNAC69 in Arabidopsis enhanced the resistance to powdery mildew Golovinomyces cichoracearum. In summary, our study indicates that TuNAC69 participates in the immune response mediated by NLR protein YrU1, and likely plays an important role in disease resistance to other pathogens.
Highlights
Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating diseases of crops that poses a major threat to the production of hexaploid wheat (Triticum aestivum L.), around the world [1,2]
To verify the results of RNA-seq, we examined the TuNAC69 transcript levels by qRT-PCR at 0 days post-inoculation, 1 dpi and 4 dpi with Pst CYR33
We found that a NAC transcription factor TuNAC69 was up-regulated after being inoculated with Pst CYR33 in the presence of YrU1
Summary
Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating diseases of crops that poses a major threat to the production of hexaploid wheat (Triticum aestivum L.), around the world [1,2]. In the effort to fight for wheat stripe rust, several stripe rust resistance genes have been identified and cloned, including Yr5/Yr7, YrSP, Yr15, Yr18/Lr34, Yr36, Yr46, YrAS2388 and YrU1 [3,4,5,6,7,8]. YrAS2388 encodes a nucleotide-binding site (NBS) and leucine-rich repeat (LRR) proteins (NLRs), and Yr5/Yr7 and YrSP encode NLR with an additional BED domain [9]. YrU1 encodes an NLR, with an N-terminal ankyrin-repeat and a C-terminal WRKY domain, which exists only in Triticum species, representing a very unique structure in plants [8]. The wheat stripe resistances mediated by those NLRs are race-specific and are generally only effective against a subset of Pst isolates. Some reports show that plant NLRs can directly interact with transcription factors, how NLRs regulate defense responses dynamically by transcription factors is still unclear [12,13,14]
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