Gene expression analysis, subcellular localization, and in planta antimicrobial activity of rice (Oryza sativa L.) defensin 7 and 8

Abstract

Defensins are a group of plant antimicrobial peptides. In a previous study, it was reported that two recombinant rice (Oryza sativa L.) defensin (OsDEF) genes (OsDEF7 and OsDEF8) produced heterologously by bacteria inhibited the growth of several phytopathogen. Here, we analyzed gene expression patterns in Thai jasmine rice (O. sativa L. ssp. indica 'KDML 105') using quantitative reverse transcription-polymerase chain reaction and compared them with those in Japanese rice (O. sativa L. ssp. japonica 'Nipponbare'). Although the cultivars exhibited similar gene expression patterns at the developmental stages examined, the expression levels differed between organs. Upon Xanthomonas oryzae pv. oryzae infection in the leaves, both OsDEFs were highly upregulated at 8 days post-infection, suggesting that they play a role in pathogen defense. Moreover, in silico analyses revealed that OsDEF expression levels were affected by drought, cold, imbibition, anoxia, and dehydration stress. Using green fluorescent protein (GFP) fusions, we found that both OsDEFs were in the extracellular compartment, confirming their functions against pathogen infection. However, when recombinant OsDEFs (without GFP) were produced in tobacco BY-2 cells or Nicotiana benthamiana leaves, they could not be detected in either the culture medium or the cells. Yet, N. benthamiana leaves infiltrated with OsDEF7 or OsDEF8 constructs exhibited in planta inhibitory activity against the phytopathogen Xanthomonas campestris pv. glycines, suggesting that recombinant OsDEFs were present. Additionally, when targeting them to the ER compartment, recombinant OsDEFs could be detected. Lower inhibitory activity was observed when recombinant OsDEFs were targeted to the ER. These results suggest that OsDEFs play a role in controlling plant diseases.

Enhanced tolerance to Phytophthora root and stem rot by over-expression of the plant antimicrobial peptide CaAMP1 gene in soybean

“…been shown to enhance tolerance to many fungal diseases in several species, including pepper [8], rice [7,9,10], potato [11], tobacco [3], and creeping bentgrass and citrus [12,13]. In addition, a defensin from chickpea, which is a type of AMP, confers tolerance against water deficit stress in Arabidopsis thaliana [14].…”

Enhanced tolerance to Phytophthora root and stem rot by over-expression of the plant antimicrobial peptide CaAMP1 gene in soybean

“…AMPs are known to play important roles in constitutive or induced resistance to various pathogens, by degrading fungal cell walls, inducing membrane channel and pore formation, inhibiting DNA synthesis and cell cycle, and damaging cellular ribosomes [3−7]. Plant AMPs have been shown to enhance tolerance to many fungal diseases in several species, including pepper [8], rice [7,9,10], potato [11], tobacco [3], and creeping bentgrass and citrus [12,13]. In addition, a defensin from chickpea, which is a type of AMP, confers tolerance against water de cit stress in Arabidopsis thaliana [14].…”

“…atroseptica, and weaken the activity of the phytopathogenic fungi Helminthosporium oryzae and F. oxysporum f. sp. cubense [7,9]. Protein extracts with MSI-99, an AMP expressed in chloroplasts of tobacco, could signi cantly suppress two rice blast isolates, both in vitro and in vivo [10].…”

Enhanced tolerance to Phytophthora root and stem rot by over-expression of the plant antimicrobial peptide CaAMP1 gene in soybean

“…membrane channel and pore formation, inhibition of DNA synthesis, damage to cellular ribosomes, and inhibition of the cell cycle [3−7]. Plant AMPs are collected to enhance tolerance to fungal disease in a wide variety of species, including pepper [8] (Lee et al 2008), rice [7,9,10], potato [11], tobacco [3], and creeping bentgrass and citrus [12,13]. In addition, plant AMP, which is a defensin from chickpea, confers tolerance to water deficit stress in Aradopsis thaliana [14].…”

“…atroseptica, and simultaneously weaken the activity of the phytopathogenic fungi Helminthosporium oryzae and Fusarium oxysporum f. sp. cubense [7,9]. Protein extracts of the antimicrobial peptide MSI-99 expressed in chloroplasts of tobacco have significantly suppressive effects against two rice blast isolates, both in vitro and in vivo [10].…”