Wheat Apoplast-Localized Lipid Transfer Protein TaLTP3 Enhances Defense Responses Against Puccinia triticina

Plant apoplast serves as the frontier battlefield of plant defense in response to different types of pathogens. Many pathogenesis-related (PR) proteins are accumulated in apoplastic space during the onset of plant–pathogen interaction, where they act to suppress pathogen infection. In this study, we found the expression of Triticum aestivum lipid transfer protein 3 (TaLTP3) gene was unregulated during incompatible interaction mediated by leaf rust resistance genes Lr39/41 at the early infection stage. Stable transgenic wheat lines overexpressing TaLTP3 exhibited enhanced resistance to leaf rust pathogen Puccinia triticina. Transcriptome analysis revealed that overexpression of TaLTP3 specifically activated the transcription of pathogenesis-related protein 1a (TaPR1a) and multiple plant hormone pathways, including salicylic acid (SA), jasmonic acid (JA), and auxin, in response to the infection of the model bacterial pathogen Pseudomonas syringae pv. tomato DC3000. Further investigation indicated that TaLTP3 physically associated with wheat TaPR1a protein in the apoplast. Transgenic wheat lines overexpressing TaLTP3 and TaPR1a showed higher accumulations of reactive oxygen species (ROS) during plant defense responses. All these findings suggested that TaLTP3 is involved in wheat resistance against leaf rust pathogen infection and forming a TaLTP3-TaPR1a complex in apoplast against this pathogen, which provides new insights into the functional roles of PR proteins.

Transformation of immature wheat germ (Triticum aestivum L.) by particle bombardment

The aim of the research was to create an effective method for producing transgenic wheat plants suitable for a wide range of promising varieties, both spring and winter crops. The plant material was cultivated at temperatures ranging from 4 to 25°C, either in the dark or in the light, with a 16-hour photoperiod (16/8 - day / night). Osram L36/77 FLUORA and F36W/33 Cool White lamps were used for lighting. The composition of all nutrient media included macroand micro-salts, vitamins B5, phytohormones and carbohydrates. The pH of the medium was adjusted to 5.8 before autoclaving. The medium was sterilized in an autoclave at pressure of 1.2 atmospheres for 15 minutes. An effective method of regeneration of transgenic wheat plants for ballistic transformation has been developed. Plants obtained by this method are phenotypically normal and fully fertile. The transgenic insertion of the target gene is transmitted to the offspring in accordance with Mendel’s laws. The transformation efficiency was high for all the studied varieties and ranged from 1.4 to 7.8%.

Allelic Variations in 5' UTR of TaAFP-B Effecting the Seed Dormancy and Other Agronomic Traits in Transgenic Wheat

BackgroundTaAFP (Triticum aestivum L. ABA insensitive five binding protein) is the homology of AFP of Arabidopsis thaliana which was a negative regulator in ABA signaling and regulated embryo germination and seed dormancy. TaABI5 (Triticum aestivum L. ABA insensitive five) gene was seed-specific, and accumulated during wheat grain maturation and dormancy acquisition, which played an important role in seed dormancy. In our previous study, two allelic variants of TaAFP were identified on chromosome 2BS in common wheat, and designated as TaAFP-B1a and TaAFP-B1b. Sequence analysis showed a 4-bp insertion in the 5’UTR region of TaAFP-B1a compared with TaAFP-B1b, which affected the mRNA transcription level, mRNA decay, translation levels of GUS and tdTomatoER, GUS activity, and was significantly associated with seed dormancy in common wheat. ResultsThe results of transgenic wheats showed that: the genotypes of average GI values, plant height, grain weight of hundred and rough of second and third stem node are all significantly more in pUbi-TaAFP-BaS transformed wheat plants than in pUbi-TaAFP-BbS transformed ones, but transcript expression level. ConclusionAbove all dates indicated that the 4-bp insertion in the 5'UTR of TaAFP-B decreased the transcript expression level of TaAFP-B and the PHS resistance, and increased the plant height, grain weight of hundred and lodging resistance in this system of over expression transgenic wheat.

Current Status and Perspectives on the Application of CRISPR/Cas9 Gene-Editing System to Develop a Low-Gluten, Non-Transgenic Wheat Variety

Wheat gluten contains epitopes that trigger celiac disease (CD). A life-long strict gluten-free diet is the only treatment accepted for CD. However, very low-gluten wheat may provide an alternative treatment to CD. Conventional plant breeding methods have not been to produce celiac-safe wheat. RNA interference technology, to some extent, has succeeded in the development of safer wheat varieties. However, these varieties have multiple challenges in terms of their implementation. Clustered Regularly Interspaced Short Palindromic Repeats-associated nuclease 9 (CRISPR/Cas9) is a versatile gene-editing tool that has the ability to edit immunogenic gluten genes. So far, only a few studies have applied CRISPR/Cas9 to modify the wheat genome. In this article, we reviewed the published literature that applied CRISPR/Cas9 in wheat genome editing to investigate the current status of the CRISPR/Cas9 system to produce a low-immunogenic wheat variety. We found that in recent years, the CRISPR/Cas9 system has been continuously improved to edit the complex hexaploid wheat genome. Although some reduced immunogenic wheat varieties have been reported, CRISPR/Cas9 has still not been fully explored in terms of editing the wheat genome. We conclude that further studies are required to apply the CRISPR/Cas9 gene-editing system efficiently for the development of a celiac-safe wheat variety and to establish it as a “tool to celiac safe wheat.”

Down-expression of TaPIN1s Increases the Tiller Number and Grain Yield in Wheat

Background Tiller number is a factor determining panicle number and grain yield in wheat (Triticum aestivum). Auxin plays an important role in the regulation of branch production. PIN-FORMED 1 (PIN1), an auxin efflux carrier, plays a role in the regulation of tiller number in rice (Oryza sativa); however, little is known on the roles of PIN1 in wheat. Results Nine homologs of TaPIN1 genes were identified in wheat, of which TaPIN1-6 genes showed higher expression in the stem apex and young leaf in wheat, and the TaPIN1-6a protein was localized in the plasma membrane. The down-expression of TaPIN1s increased the tiller number in TaPIN1-RNA interference (TaPIN1-RNAi) transgenic wheat plants, indicating that auxin might mediate the axillary bud production. By contrast, the spikelet number, grain number per panicle, and the 1000-grain weight were decreased in the TaPIN1-RNAi transgenic wheat plants compared with those in the wild type. In summary, a reduction of TaPIN1s expression increased the tiller number and grain yield per plant of wheat. Conclusions Phylogenetic analysis and protein structure of nine TaPIN1 proteins were analyzed, and subcellular localization of TaPIN1-6a was located in the plasma membrane. Knock-down expression of TaPIN1 genes increased the tiller number of transgenic wheat lines. Our study suggests that TaPIN1s is required for the regulation of grain yield in wheat.

Down-expression of TaPIN1s Increases the Tiller Number and Grain Yield in Wheat

Background: Tiller number is a factor determining panicle number and grain yield in wheat (Triticum aestivum L.). Auxin plays an important role in the regulation of branch production. PIN-FORMED 1 (PIN1), an auxin efflux carrier, plays a role in the regulation of tiller number in rice (Oryza sativa); however, little is known on the roles of PIN1 in wheat. Results: Nine homologs of TaPIN1 genes were identified in wheat, of which TaPIN1-6 genes showed higher expression in the stem apex and young leaf in wheat, and the TaPIN1-6a protein was localized in the plasma membrane. The down-expression of TaPIN1s increased the tiller number in TaPIN1-RNA interference (TaPIN1-RNAi) transgenic wheat plants, indicating that auxin might mediate the axillary bud production. By contrast, the spikelet number, grain number per panicle, and the 1000-grain weight were decreased in the TaPIN1-RNAi transgenic wheat plants compared with those in the wild type. Conclusions: Phylogenetic analysis and expression patterns of nine TaPIN1 genes, and their protein structures and subcellular localization of TaPIN1-6a protein were analyzed. Down-regulated expression of TaPIN1 genes increased the tiller numbers of transgenic wheat lines. Our study suggests that TaPIN1s is required for the regulation of grain yield in wheat.