Bioscience Methods 2026, Vol.17, No.1, 9-22 http://bioscipublisher.com/index.php/bm 12 Another group is pathogenesis-related (PR) genes, which produce antimicrobial proteins. Transcriptome data show that pineapple can make chitinases and glucanases when attacked by pathogens (Sapak et al., 2021). The exact number of PRgenes is not well known, but pineapple probably has several PR1, PR2, and PR5 genes, which work in the salicylic acid defense pathway. Regulatory genes also play roles. Pineapple has 54 WRKY transcription factor genes, fewer than Arabidopsis (72) or rice (105) (Chen et al., 2019). This may also be largely due to its genome history without recent duplications. Some WRKY genes, such as AcWRKY28, have been studied and can improve stress tolerance when overexpressed (Zhou et al., 2024). Pineapple also carries genes for hormone pathways, such as salicylic acid and jasmonate, and for secondary metabolism, such as phenylpropanoid enzymes. For instance, phenylalanine ammonia-lyase (PAL) genes may help build stronger cell walls and improve resistance to pathogens (Rivera-Toro et al., 2025). In short, pineapple has fewer resistance genes overall, but important groups like NBS-LRR, PR, WRKY, and hormone regulators are present. These genes can be targets for CRISPR/Cas9, either to remove susceptibility genes or to boost positive defense genes. 2.3 Disease-related defense pathways in pineapple When pathogens attack, pineapple may turn on defense systems much like those in other plants. These include hormone signals and kinase chains. The main hormones are salicylic acid (SA), jasmonic acid (JA), and ethylene (ET). In many plants, SA mainly fights biotrophic pathogens, while JA and ET defend against necrotrophs and insects (Li et al., 2019; Hou and Tsuda, 2022). Pineapple has genes such as NPR1 for SA signals and COI1/JAZ for JA signals. When SA is triggered, for example during Phytophthora infection, it can turn on PR genes like AcPR1 and cause systemic resistance (Sapak et al., 2021; Tian et al., 2025). Wounds or insect feeding can start the JA/ET pathways, leading to proteins such as protease inhibitors. These hormone pathways can affect each other. High SA may weaken JA defense, and high JA may reduce SA activity (Li et al., 2019). Pineapple also seems to use MAPK cascades to carry danger signals from the cell surface to the nucleus. In other plants, sensing pathogens turns on MAPKs, which then trigger defense gene expression (Hou and Tsuda, 2022; Zhang et al., 2025). The pineapple genome carries MAPKKK, MAPKK, and MAPKgenes. MAPK3/6-like genes may turn on WRKY transcription factors, which can boost defenses such as oxidative bursts or stronger cell walls. PAL genes in these pathways may raise lignin content, which in tomato has been linked to better resistance (Rivera-Toro et al., 2025). In short, pineapple makes use of common plant defense routes—SA, JA, and ET hormone signals, along with MAPK pathways. Genome editing can work on these points to improve resistance, either by removing blockers or by boosting helpers (Tian et al., 2025). Using knowledge of these pathways together with genome data can guide better strategies for stronger immunity. 3 Success Stories of CRISPR/Cas9 Disease Resistance in Other Crops 3.1Grape (Vitis vinifera) – resistance to powdery mildew via MLOgene knockout Powdery mildew, caused by Erysiphe necator, is a serious grape disease. CRISPR has been used to give grapes resistance by knocking out MLOgenes, which are susceptibility genes. In grape, VvMLO3 and VvMLO7 help the fungus infect plants. When these genes lose function, plants become resistant, as seen before in barley. Wan et al. (2020) used CRISPR/Cas9 to edit VvMLO3 and VvMLO4 in ‘Thompson Seedless’ grapes. They used Agrobacterium to deliver Cas9 and sgRNA into embryogenic callus, creating small indels. The edited plants had much better mildew resistance in greenhouse tests, with fewer lesions and spores than wild type (Figure 2). There were no major growth problems, apart from improved resistance.
RkJQdWJsaXNoZXIy MjQ4ODYzNA==