| In plant and animals, AMP (antimicrobial peptide) is a key defense barrier against microbial invasion and keeps a vital role in innate immunity. The antimicrobial peptide sources are plentiful and many of them remain to be explored and utilized. Especially, a few of effective antifungal peptides were yet reported by now. The agro-borne Fusarium wilts severely affect the crops and there are no more effective prevention and control on this devasting disease. In particular, prevalent banana wilt caused by F. oxysporum f.sp. cubense trace 4(Foc-TR4) is indulging in the banana planting region worldwide and threatens the 80 present banana crops. Herein, the finding of the more resistance against banana wilt conferred by BBTV-infected banana, indicates that BBTV may antagonize against Foc in both inhabiting vasculature. Further,The BBTV suppressor of gene silencing (i.e. B4) which specifically locating in the outer membrane of vascular tissue, displays antifungal activity towards F. oxysporum in vitro. The purified B4 can inhibit the majority (>90%) of conidial germination and the growth of hyphae. Furthermore, transgenic tomatoes expressing B4GFP enhanced resistance to F. oxysporum f.sp. lycopersici (Fol). Differential gene expression analysis showed that the transcriptional level of photogenesis-related gene in dark green leaves of B4GFP-modified tomato plants has significantly increased by 50-fold relative to those found in WT plants imperiled by Fol. Conversely, transcript abundance of immunity-related genes was substantially lower in transgenic tomatoes in contast to the WT plants, suggesting thathindrance of primary Fusarium invasion by B4 protein could not result in massive activation of ETI (effector-triggered immunnity). This viral-fungal interaction provides new insight into microbial community dynamics within a single host.In addition, bacterial diseases severely affect the plant crops and bactericide-resistance give rise to urgent issue of disease prevention and control. But the resistant bacterial stain generally should be susceptible to AMP due that AMPs directly target one specific component of cellular plasma. Hemocyanins present in invertebrate hemolymph are multifunctional proteins, responsible for oxygen transport and contributing to innate immunity through phenoloxidase-like activity. In arthropods, haemocyanin has been identified as a source of broad-spectrum antimicrobial peptides during infection. Conversely, no haemocyanin-derived antimicrobial peptides have been reported for molluscs. The present study describes a putative antimicrobial region, termed haliotisin, located within the linking sequence between the α-helical domain and β-sheet domain of abalone (Haliotis tuberculata) haemocyanin functional unit E. A series of synthetic peptides based on overlapping fragments of the haliotisin region were tested for their bactericidal potential. Incubating Gram-positive and Gram-negative bacteria in the presence of certain haliotisin peptides, notably peptides 3-4-5(DTFDYKKFGYRYDSLELEGRSISRID ELIQQRQEKDRTFAGFLLKGFGTSAS) led to reductions in microbial growth. Furthermore, transmission electron micrographs of haliotisin-treated bacteria revealed damages to the microbial cell wall. Data discussed here provides the first evidence to suggest abalone haemocyanin may act as a source of novel broad-spectrum antimicrobial peptide, but its antimicrobial mechanism remains to be further identified.In this dissertation, the first identification of viral antifungal protein B4 and Hc-derived antibacterial peptide haliotisin have both been ascertificated at first. The two belong to the antimicrobial immune molecules, providing the unique resistant source for transgenic breeding against Fusarium-related wilt and bacterial disease respectively. |
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