Fatty Acid Desaturases in the Chloroplast and Endoplasmic Reticulum Promote Susceptibility to the Green Peach Aphid Myzus persicae in Arabidopsis thaliana.

Fatty acid desaturases (FADs) in plants influence levels of susceptibility to multiple stresses, including insect infestations. In this study, populations of the green peach aphid (Myzus persicae) on Arabidopsis thaliana were reduced by mutations in three desaturases: AtFAB2/SSI2, which encodes a chloroplastic stearoyl-[acyl-carrier-protein] 9-desaturase, and AtFAD7 or AtFAD3, which encode ω-3 FADs in the chloroplast and endoplasmic reticulum (ER), respectively. These data indicate that certain FADs promote susceptibility to aphids and that aphids are impacted by desaturases in both the chloroplast and ER. Aphid resistance in ssi2, fad3, and fad7, singly or in combination, might involve altered signaling between these subcellular compartments. C18:1 levels are depleted in ssi2, whereas C18:2 accumulation is enhanced in fad3 and fad7. In contrast, fad8 has higher than normal C18:2 levels but also high C18:1 and low C18:0 and does not impact aphid numbers. Potentially, aphids may be influenced by the balance of multiple fatty acids (FAs) rather than by a single species, with C18:2 promoting aphid resistance and C18:1 promoting susceptibility. Although the fad7 mutant also accumulates higher-than-normal levels of C16:2, this FA does not contribute to aphid resistance because a triple mutant line that lacks detectable levels of C16:2 (fad2fad6fad7) retains comparable levels of aphid resistance as fad7. In addition, aphid numbers are unaffected by the fad5 mutation that inhibits C16:1 synthesis. Together, these results demonstrate that certain FADs are important susceptibility factors in plant-aphid interactions and that aphid resistance is more strongly associated with differences in C18 abundance than C16 abundance.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

WFhb1-1 plays an important role in resistance against Fusarium head blight in wheat.

Fusarium head blight (FHB) is a severe disease of wheat (Triticum aestivum L.). Qfhb1 is the most important quantitative trait locus (QTL) for FHB resistance. We previously identified wheat gene WFhb1-1 (aka WFhb1-c1) as a candidate for FHB resistance gene. Here we report that WFhb1-1 has been cloned. The gene (GenBank # KU304333.1) consists of a single exon, encoding a putative membrane protein of 127 amino acids. WFhb1-1 protein produced in Pichia pastoris inhibits growth of both F. graminearum and P. pastoris in culture. Western Blotting with anti- WFhb1-1 antibody revealed a significant decrease (p < 0.01) in WFhb1-1 accumulation, 12 hours post Fusarium inoculation in non-Qfhb1-carrier wheat but not in Qfhb1-carrier wheat. Overexpressing WFhb1-1 in non-Qfhb1-carrier wheat led to a significant decrease (p < 0.01) in Fusarium-damaged rachis rate, Fusarium-diseased kernel rate and DON content in harvested kernels, while silencing WFhb1-1 in Qfhb1-carrier wheat resulted in a significant increase (p < 0.01) in FHB severity. Therefore, WFhb1-1 is an important FHB resistance gene with a potential antifungal function and probably a key functional component of Qfhb1 in wheat. A model regarding how WFhb1-1 functions in FHB resistance/susceptibility is hypothesized and discussed.

The FATTY ACID DESATURASE2 Family in Tomato Contributes to Primary Metabolism and Stress Responses.

The conversion of oleic acid (C18:1) to linoleic acid (C18:2) in the endoplasmic reticulum is critical to the accumulation of polyunsaturated fatty acids in seeds and other tissues, and this reaction is catalyzed by a Δ12-desaturase, FATTY ACID DESATURASE2 (FAD2). Here, we report that the tomato (Solanum lycopersicum) genome harbors two genes, SlFAD2-1 and SlFAD2-2, which encode proteins with in vitro Δ12-desaturase activity. In addition, tomato has seven divergent FAD2 members that lack Δ12-desaturase activity and differ from canonical FAD2 enzymes at multiple amino acid positions important to enzyme function. Whereas SlFAD2-1 and SlFAD2-2 are downregulated by biotic stress, the majority of divergent FAD2 genes in tomato are upregulated by one or more stresses. In particular, SlFAD2-7 is induced by the potato aphid (Macrosiphum euphorbiae) and has elevated constitutive expression levels in suppressor of prosystemin-mediated responses2 (spr2), a tomato mutant with enhanced aphid resistance and altered fatty acid profiles. Virus-induced gene silencing of SlFAD2-7 in spr2 results in significant increases in aphid population growth, indicating that a divergent FAD2 gene contributes to aphid resistance in this genotype. Thus, the FAD2 gene family in tomato is important both to primary fatty acid metabolism and to responses to biotic stress.

Harnessing Genome Editing Techniques to Engineer Disease Resistance in Plants.

Modern genome editing (GE) techniques, which include clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (CRISPR/Cas9) system, transcription activator-like effector nucleases (TALENs), zinc-finger nucleases (ZFNs) and LAGLIDADG homing endonucleases (meganucleases), have so far been used for engineering disease resistance in crops. The use of GE technologies has grown very rapidly in recent years with numerous examples of targeted mutagenesis in crop plants, including gene knockouts, knockdowns, modifications, and the repression and activation of target genes. CRISPR/Cas9 supersedes all other GE techniques including TALENs and ZFNs for editing genes owing to its unprecedented efficiency, relative simplicity and low risk of off-target effects. Broad-spectrum disease resistance has been engineered in crops by GE of either specific host-susceptibility genes (S gene approach), or cleaving DNA of phytopathogens (bacteria, virus or fungi) to inhibit their proliferation. This review focuses on different GE techniques that can potentially be used to boost molecular immunity and resistance against different phytopathogens in crops, ultimately leading to the development of promising disease-resistant crop varieties.

The Genetics and Genome-Wide Screening of Regrowth Loci, a Key Component of Perennialism in Zea diploperennis.

Perennialism is common among the higher plants, yet little is known about its inheritance. Previous genetic studies of the perennialism in Zea have yielded contradictory results. In this study, we take a reductionist approach by specifically focusing on one trait: regrowth (the plant's ability to restart a new life cycle after senescence on the same body). To address this, six hybrids were made by reciprocally crossing perennial Zea diploperennis Iltis, Doebley & R. Guzman with inbred lines B73 and Mo17 and Rhee Flint, a heirloom variety, of Zmays L. ssp. mays All the F1 plants demonstrated several cycles of growth, flowering, senescence and regrowth into normal flowering plants, indicating a dominant effect of the Z. diploperennis alleles. The regrowability (i.e., the plants' ability to regrow after senescence) was stably transmitted to progeny of the hybrids. Segregation ratios of regrowth in the F2 generations are consistent with the trait controlled by two dominant, complementary loci, but do not exclude the influence of other modifiers or environment. Genome-wide screening with genotyping-by-sequencing technology indicated two major regrowth loci, regrowth 1 (reg1) and regrowth 2 (reg2), were on chromosomes 2 and 7, respectively. These findings lay the foundation for further exploration of the molecular mechanism of regrowth in Z. diploperennis Importantly, our data indicate that there is no major barrier to transferring this trait into maize or other grass crops for perennial crop development with proper technology, which enhances sustainability of grain crop production in an environmentally friendly way.