构成性表达（constitutive expression）

The NAC (NAM, ATAF and CUC) family is one of the largest plant-specific transcription factor (TF) families. Members of this family are implicated in plant growth, development and stress responses. Recent functional studies demonstrate that a number of NAC TFs function as positive or negative regulators of plant immunity to biotrophic, hemibiotrophic or necotrophic pathogens, as modulators of the hypersensitive responses and stomatal immunity or as virulence targets of pathogen effectors. They affect plant immunity through their regulatory impact on signaling of plant hormones, which in turn are key players in plant immune responses. This review summarizes current knowledge and recent progress in our understanding of the biological functions of NAC TFs in plant immunity and discusses perspectives and directions for further study to elucidate the molecular mechanisms of NAC TF functions in immunity and potential application in improvement of crop disease resistance.

/pdf/nac-transcription-factors-in-plant-immunity-2aujn14mkd.pdf

NAC transcription factors in plant immunity

The spot blotch disease of wheat is caused by Bipolaris sorokiniana, which is an anamorph (teleomorph Cochliobolus sativus). The disease mainly occurs in warm humid wheat growing regions, and the Eastern Gangetic Plains (EGP) of South Asia is a hotspot. Significant progress has been made in recent years in characterizing the host-pathogen interaction. The study of the pathogen's life cycle and diversity have been an active area of research. A number of resistance sources have also been identified, characterized and utilized for breeding. Although immunity has not been observed in any genotype, cultivars displaying a relatively high level of resistance have been developed and made available to farmers. Further progress will require a regular use of marker-assisted breeding, genomic selection gene editing and transgenic interventions. This review summarizes the current state of knowledge about genetic and breeding efforts on wheat-B. sorokiniana pathosystem and discusses ways in which emerging tools can be used for future research to understand the mechanism involved in infection and for developing cultivars exhibiting a high level of resistance.

This article is protected by copyright. All rights reserved.

https://bsppjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/ppa.12781

Spot blotch disease of wheat: the current status of research on genetics and breeding

Background
Fusarium head blight (FHB) caused by Fusarium graminearum not only causes severe losses in yield, but also reduces quality of wheat grain by accumulating mycotoxins. Breeding for host plant resistance is considered as the best strategy to manage FHB. Resistance in wheat to FHB is quantitative in nature, involving cumulative effects of many genes governing resistance. The poor understanding of genetics and lack of precise phenotyping has hindered the development of FHB resistant cultivars. Though more than 100 QTLs imparting FHB resistance have been reported, none discovered the specific genes localized within the QTL region, nor the underlying mechanisms of resistance.

/pdf/integrated-metabolo-transcriptomics-reveals-fusarium-head-3gyun20ilz.pdf

Integrated Metabolo-Transcriptomics Reveals Fusarium Head Blight Candidate Resistance Genes in Wheat QTL-Fhb2.

Genome editing tools are important for functional genomics research and biotechnology applications. Recently, the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 (Cas9) system for gene knockout has emerged as the most effective genome-editing tool. It has previously been reported that, in rice plants, knockdown of the Os8N3 gene resulted in enhanced resistance to Xanthomonas oryzae pv. oryzae (Xoo), while displaying abnormal pollen development. The CRISPR/Cas9 system was employed to knockout rice Os8N3, in order to confer enhanced resistance to Xoo. Analysis of the genotypes and edited Os8N3 in T0, T1, T2, and T3 transgenic rice plants showed that the mutations were transmitted to subsequent generations, and homozygous mutants displayed significantly enhanced resistance to Xoo. Stable transmission of CRISPR/Cas9-mediated Os8N3 gene editing without the transferred DNA (T-DNA) was confirmed by segregation in the T1 generation. With respect to many investigated agronomic traits including pollen development, there was no significant difference between homozygous mutants and non-transgenic control plants under greenhouse growth conditions. Data from this study indicate that the CRISPR/Cas9-mediated Os8N3 edition can be successfully employed for non-transgenic crop improvements.

/pdf/crispr-cas9-targeted-mutagenesis-of-os8n3-in-rice-to-confer-2ys56b10ry.pdf

CRISPR/Cas9-targeted mutagenesis of Os8N3 in rice to confer resistance to Xanthomonas oryzae pv. oryzae.

Plant-specific NAC transcription factors 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 transcription factor 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, 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 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.

/pdf/tanac1-acts-as-a-negative-regulator-of-stripe-rust-2htq7upugh.pdf

TaNAC1 acts as a negative regulator of stripe rust resistance in wheat, enhances susceptibility to Pseudomonas syringae, and promotes lateral root development in transgenic Arabidopsis thaliana

Wheat bHLH transcription factor gene, TabHLH060, enhances susceptibility of transgenic Arabidopsis thaliana to Pseudomonas syringae

Basic leucine zipper (bZIP) membrane-bound transcription factors (MTFs) play important roles in regulating plant growth and development, abiotic stress responses, and disease resistance. Most bZIP MTFs are key components of signaling pathways in endoplasmic reticulum (ER) stress responses. In this study, a full-length cDNA sequence encoding bZIP MTF, designated TabZIP74, was isolated from a cDNA library of wheat near-isogenic lines of Taichung29*6/Yr10 inoculated with an incompatible race CYR32 of Puccinia striiformis f. sp. tritici (Pst). Phylogenic analysis showed that TabZIP74 is highly homologous to ZmbZIP60 in maize and OsbZIP74 in rice. The mRNA of TabZIP74 was predicted to form a secondary structure with two kissing hairpin loops that could be spliced, causing an open reading frame shift immediately before the hydrophobic region to produce a new TabZIP74 protein without the transmembrane domain. Pst infection and the abiotic polyethylene glycol (PEG) and abscisic acid (ABA) treatments lead to TabZIP74 mRNA splicing in wheat seedling leaves, while both spliced and unspliced forms in roots were detected. In the confocal microscopic examination, TabZIP74 is mobilized in the nucleus from the membrane of tobacco epidermal cells in response to wounding. Knocking down TabZIP74 with barley stripe mosaic virus-induced gene silencing (BSMV-VIGS) enhanced wheat seedling susceptibility to stripe rust and decreased drought tolerance and lateral roots of silenced plants. These findings demonstrate that TabZIP74 mRNA is induced to splice when stressed by biotic and abiotic factors, acts as a critically positive regulator for wheat stripe rust resistance and drought tolerance, and is necessary for lateral root development.

/pdf/tabzip74-acts-as-a-positive-regulator-in-wheat-stripe-rust-2v8u1izish.pdf

TabZIP74 Acts as a Positive Regulator in Wheat Stripe Rust Resistance and Involves Root Development by mRNA Splicing

Spot blotch, caused by the fungal pathogen Cochliobolus sativus, is a limiting factor for barley (Hordeum vulgare) production in northeast China, which causes significant grain yield losses and kernel quality degradation. It is critical to determine the virulence diversity of C. sativus populations for barley resistance breeding and the judicious grouping of available resistance varieties according to the predominant pathotypes in disease epidemic regions. With little information on the barley pathogen in China, this study selected 12 typical barley genotypes to differentiate the pathotypes of C. sativus isolates collected in China. Seventy-one isolates were grouped into 19 Chinese pathotypes based on infection responses. Seventeen isolates were classified as pathotype 3, which has only been identified in China, whereas most (52 of 71) were classified as pathotype 1. All of the tested isolates had low virulence on the North Dakota (ND) durable, resistant line ND B112. Using 22 selected amplified fragment-length polymorphism (AFLP) primer combinations, genetic polymorphism was used to analyze 68 isolates, which clustered into three distinct groups using the unweighted pair group method average with the genetic distance coefficient. No relationship was found between the virulence of isolates and their origins. Isolates of the same pathotype or those collected from the same location did not group into clusters based on the AFLP analysis.

/pdf/virulence-and-molecular-diversity-in-the-cochliobolus-49z1gp5w07.pdf

Virulence and Molecular Diversity in the Cochliobolus sativus Population Causing Barley Spot Blotch in China

Wheat stripe (yellow) rust, caused by Puccinia striiformis West. f. sp. tritici (Pst), is one of the most destructive diseases in many wheat-growing countries, especially in China, the largest stripe rust epidemic area in the world. Growing the resistant cultivars is an effective, economic and environmentally friendly way to control this disease. Wheat cultivar Zhengmai 7698 has shown a high-level resistance to wheat stripe rust. To elucidate its genetic characteristics and location of the resistance gene, Zhengmai 7698 was crossed with susceptible variety Taichung 29 to produce $$\hbox {F}_{{1}}$$
 , $$\hbox {F}_{{2}}$$
 and $$\hbox {BC}_{{1}}$$
 progeny generations. The genetic analysis showed that the stripe rust resistance in Zhengmai 7698 to Pst predominant race CYR32 was controlled by a single-dominant gene, namedYrZM. Bulked segregant analysis and simple sequence repeat (SSR) markers were used to map the gene. Four SSR markers, Xbarc198, Xwmc179, Xwmc786 and Xwmc398 on chromosome 6BL were polymorphic between the parents and resistance, and susceptible bulks. A linkage genetic map was constructed using 212 $$\hbox {F}_{{2}}$$
 plants in the sequential order of Xwmc398, Xwmc179, YrZM, Xbarc198, Xwmc786. As this gene is effective against predominant race CYR32, it is useful in combination with other resistance genes for developing new wheat cultivars with resistance to stripe rust.

Shichang Xu

Papers

TaNAC1 acts as a negative regulator of stripe rust resistance in wheat, enhances susceptibility to Pseudomonas syringae, and promotes lateral root development in transgenic Arabidopsis thaliana

Wheat bHLH transcription factor gene, TabHLH060, enhances susceptibility of transgenic Arabidopsis thaliana to Pseudomonas syringae

TabZIP74 Acts as a Positive Regulator in Wheat Stripe Rust Resistance and Involves Root Development by mRNA Splicing

Virulence and Molecular Diversity in the Cochliobolus sativus Population Causing Barley Spot Blotch in China

Genetic analysis and location of a resistance gene for Puccinia striiformis f. sp. tritici in wheat cultivar Zhengmai 7698.