Large-Scale Cloning and Comparative Analysis of TaNAC Genes in Response to Stripe Rust and Powdery Mildew in Wheat (Triticum aestivum L.)

Abstract

The NAM, ATAF1/2, and CUC2 (NAC) transcription factors (TFs) constitute the largest plant-specific TF superfamily, and play important roles in various physiological processes, including stress responses. Stripe rust and powdery mildew are the most damaging of the fungal diseases that afflict wheat (Triticum aestivum L.). However, studies on Triticum aestivum NAC (TaNAC)s’ role in resistance to the two diseases are still limited, especially in an overall comparative analysis of TaNACs responding or not to fungal stress. In the present study, 186 TaNAC transcripts were obtained from the resistant hexaploid wheat line N9134 under fungal stress, and 180 new transcripts were submitted to GenBank. Statistical results show that 35.1% (54/154) of TaNAC genes responded to stripe rust and powdery mildew in the seedling stage. “Abnormal” coding transcripts of differentially expressed (DE)-TaNAC genes in wheat responding to fungal stress were found in a significantly higher proportion (24/117 vs. 8/69, p = 0.0098) than in non-DE-NACs. This hinted that the alternative splicing of TaNAC genes was active in transcriptional or post-transcriptional regulation during plant-pathogen interactions. Full-length NAC proteins were classified into nine groups via phylogenetic analysis. Multiple-sequence alignment revealed diversity in the C-terminal structural organization, but the differentially expressed gene (DEG)-encoding proteins enriched in Subgroups VI and VII were conserved, with WV[L/V]CR amino acid residues in Motif 7 following the NAM domain. Our data that showed TaNAC TFs responded to fungal disease, which was affected by expression levels and by the regulation of multifarious transcript variants. These data for TaNAC responses to stripe rust and/or powdery mildew and their numerous structural variants provide a good resource for NAC function–mechanism analysis in the context of biotic-stress tolerance in wheat.

Comprehensive analysis of pathogen-responsive wheat NAC transcription factors: new candidates for crop improvement

“…Four studies identified high confidence Triticum aestivum (wheat) NAC s ( TaNAC s) in the cultivar Chinese Spring; Borrill et al (2017) identified 453 TaNAC genes in the TGACv1 genome assembly, while Guérin et al (2019) and Ma et al (2021) identified, respectively, 460 and 462 TaNAC s using a more recent assembly (RefSeq v1.0) and Lv et al (2020) identified 460 TaNAC s in the RefSeq v1.1 genome annotation. Studies from Borrill et al (2017) and Guérin et al (2019) mined RNA-sequencing (RNA-seq) datasets to determine the expression profiles of TaNAC s in different tissues, and in response to biotic and/or abiotic stresses.…”

“…Studies from Borrill et al (2017) and Guérin et al (2019) mined RNA-sequencing (RNA-seq) datasets to determine the expression profiles of TaNAC s in different tissues, and in response to biotic and/or abiotic stresses. Borrill et al (2017) delineated TaNAC s responsive to biotic stress, while other studies ( Lv et al 2020 ; Ma et al 2021 ) delineated TaNAC genes responsive to specific pathogens, i.e. races of the causal agents of stripe rust disease ( Puccinia striiformis f. sp.…”

NAC Transcription Factors as Positive or Negative Regulators during Ongoing Battle between Pathogens and Our Food Crops

“…NAC TFs constitute one of the largest groups of plant-specific TFs, with more than 100 members in most plants, including model plants like Arabidopsis or most crops, and the highest reported number of 559 in wheat [ 23 ]. The NAC acronym is derived from three reported proteins that contain a highly conserved domain in their N-terminal region (the NAC domain): (i) NAM (No Apical Meristem), (ii) ATAF1/2 ( Arabidopsis thaliana Transcription Activator Factor 1/2) and (iii) CUC2 (Cup-shaped Cotyledon 2) [ 20 , 21 ].…”

“…Thus, it is quite urgent to develop novel wheat varieties that have improved yield potential and increased tolerances to biotic and abiotic stresses. There are 559 TaNAC genes in the wheat genome, 186 of which were recently identified during infection of the resistant hexaploid wheat line N9134 with the fungal agents that cause rust and powdery mildew [ 23 ].…”

“…Barley ( Hordeum vulgare ) and soybean ( Glycine max ) are also important crops, in the grain and legume families, while tomato ( Solanum lycopersicum ) is a fruit crop. NAC TFs comprise a gene family with 151 members in rice [ 19 , 20 , 21 ], 157 in maize [ 22 ], 559 in wheat [ 23 ], 167 in barley [ 24 ], 152 in soybean [ 25 ], and 93 in tomato [ 26 ]. Recent studies demonstrate that NAC TFs can be induced by pathogen infection, regulate the expression of downstream genes, and integrate hormone and other signals to offer plants resistance against pathogens.…”