Contrasting genetic variation and positive selection followed the divergence of NBS-encoding genes in Asian and European pears

Functional characterization of NBS-LRR genes reveals an NBS-LRR gene that mediates resistance against Fusarium wilt

BACKGROUND

Most disease resistance (R) genes in plants encode proteins that contain leucine-rich-repeat (LRR) and nucleotide-binding site (NBS) domains, which belong to the NBS-LRR family. The sequenced genomes of Fusarium wilt-susceptible Vernicia fordii and its resistant counterpart, Vernicia montana, offer significant resources for the functional characterization and discovery of novel NBS-LRR genes in tung tree.

RESULTS

Here, we identified 239 NBS-LRR genes across two tung tree genomes: 90 in V. fordii and 149 in V. montana. Five VmNBS-LRR paralogous were predicted in V. montana, and 43 orthologous were detected between V. fordii and V. montana. The orthologous gene pair Vf11G0978-Vm019719 exhibited distinct expression patterns in V. fordii and V. montana: Vf11G0978 showed downregulated expression in V. fordii, while its orthologous gene Vm019719 demonstrated upregulated expression in V. montana, indicating that this pair may be responsible for the resistance to Fusarium wilt in V. montana. Vm019719 from V. montana, activated by VmWRKY64, was shown to confer resistance to Fusarium wilt in V. montana by a virus-induced gene silencing (VIGS) experiment. However, in the susceptible V. fordii, its allelic counterpart, Vf11G0978, exhibited an ineffective defense response, attributed to a deletion in the promoter's W-box element.

CONCLUSIONS

This study provides the first systematic analysis of NBS-LRR genes in the tung tree and identifies a candidate gene that can be utilized for marker-assisted breeding to control Fusarium wilt in V. fordii.

PearMODB: a multiomics database for pear (Pyrus) genomics, genetics and breeding study

Pear (Pyrus ssp.) belongs to Rosaceae and is an important fruit tree widely cultivated around the world. Currently, challenges to cope with the burgeoning sets of multiomics data are rapidly increasing. Here, we constructed the Pear Multiomics Database (PearMODB) by integrating genome, transcriptome, epigenome and population variation data, and aimed to provide a portal for accessing and analyzing pear multiomics data. A variety of online tools were built including gene search, BLAST, JBrowse, expression heatmap, synteny analysis and primer design. The information of DNA methylation sites and single-nucleotide polymorphisms can be retrieved through the custom JBrowse, providing an opportunity to explore the genetic polymorphisms linked to phenotype variation. Moreover, different gene families involving transcription factors, transcription regulators and disease resistance (nucleotide-binding site leucine-rich repeat) were identified and compiled for quick search. In particular, biosynthetic gene clusters (BGCs) were identified in pear genomes, and specialized webpages were set up to show detailed information of BGCs, laying a foundation for studying metabolic diversity among different pear varieties. Overall, PearMODB provides an important platform for pear genomics, genetics and breeding studies. Database URL http://pearomics.njau.edu.cn.

Complete chloroplast genome features of the model heavy metal hyperaccumulator Arabis paniculata Franch and its phylogenetic relationships with other Brassicaceae species

Arabis paniculata Franch (Brassicaceae) has been widely used for the phytoremediation of heavy mental, owing to its hyper tolerance of extreme Pb, Zn, and Cd concentrations. However, studies on its genome or plastid genome are scarce. In the present study, we obtained the complete chloroplast (cp) genome of A. paniculata via de novo assembly through the integration of Illumina reads and PacBio subreads. The cp genome presents a typical quadripartite cycle with a length of 153,541 bp, and contains 111 unigenes, with 79 protein-coding genes, 28 tRNAs and 4 rRNAs. Codon usage analysis showed that the codons for leucine were the most frequent codons and preferentially ended with A/U. Synonymous (Ks) and non-synonymous (Ka) substitution rate analysis indicated that the unigenes, ndhF and rpoC2, related to "NADH-dehydrogenase" and "RNA polymerase" respectively, underwent the lowest purifying selection pressure. Phylogenetic analysis demonstrated that Arabis flagellosa and A. hirsuta are more similar to each other than to A. paniculata, and Arabis is the closest relative of Draba among all Brassicaceae genera. These findings provide valuable information for the optimal exploitation of this model species as a heavy-metal hyperaccumulator.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-022-01151-1.

Pear genetics: Recent advances, new prospects, and a roadmap for the future

Pear, belonging to the genus Pyrus, is one of the most economically important temperate fruit crops. Pyrus is an important genus of the Rosaceae family, subfamily Maloideae, and has at least 22 different species with over 5000 accessions maintained or identified worldwide. With the release of draft whole-genome sequences for Pyrus, opportunities for pursuing studies on the evolution, domestication, and molecular breeding of pear, as well as for conducting comparative genomics analyses within the Rosaceae family, have been greatly expanded. In this review, we highlight key advances in pear genetics, genomics, and breeding driven by the availability of whole-genome sequences, including whole-genome resequencing efforts, pear domestication, and evolution. We cover updates on new resources for undertaking gene identification and molecular breeding, as well as for pursuing functional validation of genes associated with desirable economic traits. We also explore future directions for "pear-omics".

Genome-wide identification of PME genes, evolution and expression analyses in soybean (Glycine max L.)

BACKGROUND

Pectin methylesterase (PME) is one of pectin-modifying enzyme that affects the pectin homeostasis in cell wall and regulates plant growth and diverse biological processes. The PME genes have been well explored and characterized in different plants. Nevertheless, systematic research on the soybean (Glycine max L.) PME genes remain lacking.

RESULTS

We identified 127 Glycine max PME genes (GmPME) from the soybean Wm82.a2.v1 genome, which unevenly distributed on 20 soybean chromosomes. Phylogenetic analysis classified the GmPME genes into four clades (Group I, Group II, Group III and Group IV). GmPME gene members in the same clades displayed similar gene structures and motif patterns. The gene family expansion analysis demonstrated that segmental duplication was the major driving force to acquire novel GmPME genes compared to the tandem duplication events. Further synteny and evolution analyses showed that the GmPME gene family experienced strong purifying selective pressures during evolution. The cis-element analyses together with the expression patterns of the GmPME genes in various tissues suggested that the GmPME genes broadly participate in distinct biological processes and regulate soybean developments. Importantly, based on the transcriptome data and quantitative RT-PCR validations, we examined the potential roles of the GmPME genes in regulating soybean flower bud development and seed germination.

CONCLUSION

In conclusion, we provided a comprehensive characterization of the PME genes in soybean, and our work laid a foundation for the functional study of GmPME genes in the future.

Dynamic Diversity of NLR Genes in Triticum and Mining of Promising NLR Alleles for Disease Resistance

Bread wheat is an essential crop with the second-highest global production after maize. Currently, wheat diseases are a serious threat to wheat production. Therefore, efficient breeding for disease resistance is extremely urgent in modern wheat. Here, we identified 2012 NLR genes from hexaploid wheat, and Ks values of paired syntenic NLRs showed a significant peak at 3.1–6.3 MYA, which exactly coincided with the first hybridization event between A and B genome lineages at ~5.5 MYA. We provided a landscape of dynamic diversity of NLRs from Triticum and Aegilops and found that NLR genes have higher diversity in wild progenitors and relatives. Further, most NLRs had opposite diversity patterns between genic and 2 Kb-promoter regions, which might respectively link sub/neofunctionalization and loss of duplicated NLR genes. Additionally, we identified an alien introgression of chromosome 4A in tetraploid emmer wheat, which was similar to that in hexaploid wheat. Transcriptome data from four experiments of wheat disease resistance helped to profile the expression pattern of NLR genes and identified promising NLRs involved in broad-spectrum disease resistance. Our study provided insights into the diversity evolution of NLR genes and identified beneficial NLRs to deploy into modern wheat in future wheat disease-resistance breeding.