Differential regulation of miRNAs involved in the susceptible and resistance responses of wheat cultivars to wheat streak mosaic virus and Triticum mosaic virus.

BACKGROUND: Wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV) are components of the wheat streak mosaic virus disease complex in the Great Plains region of the U.S.A. and elsewhere. Co-infection of wheat with WSMV and TriMV causes synergistic interaction with more severe disease symptoms compared to single infections. Plants are equipped with multiple antiviral mechanisms, of which regulation of microRNAs (miRNAs) is a potentially effective constituent. In this investigation, we have analyzed the total and relative expression of miRNA transcriptome in two wheat cultivars, Arapahoe (susceptible) and Mace (temperature-sensitive-resistant), that were mock-inoculated or inoculated with WSMV, TriMV, or both at 18 °C and 27 °C. RESULTS: Our results showed that the most abundant miRNA family among all the treatments was miRNA166, followed by 159a and 168a, although the order of the latter two changed depending on the infections. When comparing infected and control groups, twenty miRNAs showed significant upregulation, while eight miRNAs were significantly downregulated. Among them, miRNAs 9670-3p, 397-5p, and 5384-3p exhibited the most significant upregulation, whereas miRNAs 319, 9773, and 9774 were the most downregulated. The comparison of infection versus the control group for the cultivar Mace showed temperature-dependent regulation of these miRNAs. The principal component analysis confirmed that less abundant miRNAs among differentially expressed miRNAs were strongly correlated with the inoculated symptomatic wheat cultivars. Notably, miRNAs 397-5p, 398, and 9670-3p were upregulated in response to WSMV and TriMV infections, an observation not yet reported in this context. The significant upregulation of these three miRNAs was further confirmed with RT-qPCR analysis; in general, the RT-qPCR results were in agreement with our computational analysis. Target prediction analysis showed that the miRNAs standing out in our analysis targeted genes involved in defense response and regulation of transcription. CONCLUSION: Investigation into the roles of these miRNAs and their corresponding targets holds promise for advancing our understanding of the mechanisms of virus infection and possible manipulation of these factors for developing durable virus resistance in crop plants.

Genome-Wide SNP and Indel Discovery in Abaca (Musa textilis Née) and among Other Musa spp. for Abaca Genetic Resources Management.

Abaca (Musa textilis Née) is an economically important fiber crop in the Philippines. Its economic potential, however, is hampered by biotic and abiotic stresses, which are exacerbated by insufficient genomic resources for varietal identification vital for crop improvement. To address these gaps, this study aimed to discover genome-wide polymorphisms among abaca cultivars and other Musa species and analyze their potential as genetic marker resources. This was achieved through whole-genome Illumina resequencing of abaca cultivars and variant calling using BCFtools, followed by genetic diversity and phylogenetic analyses. A total of 20,590,381 high-quality single-nucleotide polymorphisms (SNP) and DNA insertions/deletions (InDels) were mined across 16 abaca cultivars. Filtering based on linkage disequilibrium (LD) yielded 130,768 SNPs and 13,620 InDels, accounting for 0.396 ± 0.106 and 0.431 ± 0.111 of gene diversity across these cultivars. LD-pruned polymorphisms across abaca, M. troglodytarum, M. acuminata and M. balbisiana enabled genetic differentiation within abaca and across the four Musa spp. Phylogenetic analysis revealed the registered varieties Abuab and Inosa to accumulate a significant number of mutations, eliciting further studies linking mutations to their advantageous phenotypes. Overall, this study pioneered in producing marker resources in abaca based on genome-wide polymorphisms vital for varietal authentication and comparative genotyping with the more studied Musa spp.

Transgenic expression of lactoferrin imparts enhanced resistance to head blight of wheat caused by Fusarium graminearum.

BACKGROUND: The development of plant gene transfer systems has allowed for the introgression of alien genes into plant genomes for novel disease control strategies, thus providing a mechanism for broadening the genetic resources available to plant breeders. Using the tools of plant genetic engineering, a broad-spectrum antimicrobial gene was tested for resistance against head blight caused by Fusarium graminearum Schwabe, a devastating disease of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) that reduces both grain yield and quality. RESULTS: A construct containing a bovine lactoferrin cDNA was used to transform wheat using an Agrobacterium-mediated DNA transfer system to express this antimicrobial protein in transgenic wheat. Transformants were analyzed by Northern and Western blots to determine lactoferrin gene expression levels and were inoculated with the head blight disease fungus F. graminearum. Transgenic wheat showed a significant reduction of disease incidence caused by F. graminearum compared to control wheat plants. The level of resistance in the highly susceptible wheat cultivar Bobwhite was significantly higher in transgenic plants compared to control Bobwhite and two untransformed commercial wheat cultivars, susceptible Wheaton and tolerant ND 2710. Quantification of the expressed lactoferrin protein by ELISA in transgenic wheat indicated a positive correlation between the lactoferrin gene expression levels and the levels of disease resistance. CONCLUSIONS: Introgression of the lactoferrin gene into elite commercial wheat, barley and other susceptible cereals may enhance resistance to F. graminearum.

Engineered plant virus resistance.

Virus diseases are among the key limiting factors that cause significant yield loss and continuously threaten crop production. Resistant cultivars coupled with pesticide application are commonly used to circumvent these threats. One of the limitations of the reliance on resistant cultivars is the inevitable breakdown of resistance due to the multitude of variable virus populations. Similarly, chemical applications to control virus transmitting insect vectors are costly to the farmers, cause adverse health and environmental consequences, and often result in the emergence of resistant vector strains. Thus, exploiting strategies that provide durable and broad-spectrum resistance over diverse environments are of paramount importance. The development of plant gene transfer systems has allowed for the introgression of alien genes into plant genomes for novel disease control strategies, thus providing a mechanism for broadening the genetic resources available to plant breeders. Genetic engineering offers various options for introducing transgenic virus resistance into crop plants to provide a wide range of resistance to viral pathogens. This review examines the current strategies of developing virus resistant transgenic plants.