Medicinal Plant Research 2024, Vol.14, No.6, 345-357 http://hortherbpublisher.com/index.php/mpr 351 This discovery reveals the key nodes of the natural resistance of Hangbaiju, and also provides theoretical support for green planting conditions without over-reliance on pesticide intervention. By screening materials with high CmWD40 expression levels or enhanced functions in natural populations, it is expected that this resistance pathway will be introduced into actual breeding, thereby cultivating Hangbaiju varieties that are more adaptable to the green prevention and control system. 5.2The CmWRKY8-1 gene of Hangbaiju negatively regulates resistance to wilt disease Hangbaiju wilt disease is caused by the fungus Fusarium oxysporum, which seriously affects its ornamental and economic value. WRKY transcription factors in plants play a key regulatory role in disease resistance signaling pathways, especially closely related to the defense mechanism related to salicylic acid (SA). Miao et al. (2023a) found that the gene CmWRKY8-1 in the WRKY transcription factor family plays an important role in regulating disease resistance. Through gene cloning and transgenic technology, the researchers constructed a chrysanthemum transgenic line overexpressing the CmWRKY8-1-VP64 fusion protein. The results showed that these transgenic plants were more susceptible to F. oxysporum infection than the wild type (Figure 3). Further studies showed that the expression of this fusion protein inhibited the expression of multiple key genes in the salicylic acid (SA) signaling pathway (e.g., PAL, EDS1, NPR1, etc.), resulting in a decrease in endogenous SA content and the expression levels of related disease resistance genes PR1, PR2, and PR5, thereby weakening the plant's systemic acquired resistance. Figure 3 Physiological phenotypes after inoculation with F. oxysporum. (A) Phenotypes at the eighth day after inoculation with F. oxysporum. (B) Phenotypes at the twelfth day after inoculation with F. oxysporum. (C) Disease severity index of plants. (D) The content of POD, CAT, PAL, and PPO on the 8th day of inoculation (Adopted from Miao et al., 2023a) Image caption: The figure systematically demonstrates that transgenic chrysanthemums overexpressing the CmWRKY8-1-VP64 fusion protein have enhanced susceptibility to Fusarium oxysporum infection. Images on the 8th and 12th days (A, B) show that transgenic plants wilt and die severely, while the wild type is only slightly affected; disease index analysis (C) quantifies the difference, with transgenic plants significantly higher than wild types; defense-related enzyme activity assays (D) show that POD, CAT, PAL, and PPO activities in transgenic plants are all reduced. The results verify that overexpression of CmWRKY8-1 weakens plant disease resistance (Adapted from Miao et al., 2023a)
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