Abstract
PtDef cloned from Populus trichocarpa contained eight cysteine domains specific to defensins. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) analysis showed that PtDef was expressed in all tissues tested, with lower expression in leaves and higher expression in petioles, stems, and roots. Purified fused PtDef inhibited Aspergillus niger, Alternaria Nees, Mucor corymbifer, Marssonina populi, Rhizopus sp., and Neurospora crassa. PtDef also inhibited the growth of Escherichia coli by triggering autolysis. PtDef overexpression in Nanlin895 poplar (Populus × euramericana cv. Nanlin895) enhanced the level of resistance to Septotinia populiperda. qRT-PCR analysis also showed that the expression of 13 genes related to salicylic acid (SA) and jasmonic acid (JA) signal transduction differed between transgenic and wild-type (WT) poplars before and after inoculation, and that PR1-1 (12–72 h), NPR1-2, TGA1, and MYC2-1 expression was higher in transgenic poplars than in WT. During the hypersensitivity response (HR), large amounts of H2O2 were produced by the poplar lines, particularly 12–24 h after inoculation; the rate and magnitude of the H2O2 concentration increase were greater in transgenic lines than in WT. Overall, our findings suggest that PtDef, a defensin-encoding gene of P. trichocarpa, could be used for genetic engineering of woody plants for enhanced disease resistance.
Highlights
Plant defensins are antibacterial peptides that play an important role in plant immunity; they are the primary barrier to invasion by pathogenic bacteria (Ganz, 2003; Zhao et al, 2011)
Growing plants are vulnerable to pathogens and prone to a variety of diseases, which threaten crop yields, the environment, and sustainable agricultural development
Bioinformatics analysis revealed that PtDef had an open reading frame (ORF) of 225 bp and encoded a 74 amino acid polypeptide
Summary
Plant defensins are antibacterial peptides that play an important role in plant immunity; they are the primary barrier to invasion by pathogenic bacteria (Ganz, 2003; Zhao et al, 2011). Animal and plant defensins evolved separately and have very different amino acid sequences and cystine connectivity (Shafee et al, 2016). Genes encoding plant defensins can be divided into those with higher and lower sequence homology; these two categories of defensins may have different biological activities (Stotz et al, 2009). Defensins Are Important Antibacterial Peptides in Immunity of 45–50 amino acid residues (∼5 kDa) and have antimicrobial activity (Vriens et al, 2014). The expression of the genes encoding plant defensins differs among tissues and upon pathogen invasion (De Coninck et al, 2015; Pothana et al, 2019). Transformation of a radish defensin gene into tobacco improved tobacco resistance to Alternaria longicornis (Terras et al, 1993), and pea defensins inhibit pathogens and fungi in pea clip epidermis and vascular bundles (Almeida et al, 2002)
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