HpaXpm, a novel harpin of Xanthomonas phaseoli pv. manihotis, acts as an elicitor with high thermal stability, reduces disease, and promotes plant growth

Abstract

Background: Harpins are proteins secreted by the type III secretion system of Gram-negative bacteria during pathogen-plant interactions that can act as elicitors, stimulating defense and plant growth in many types of nonhost plants. Harpin-treated plants have higher resistance, quality and yields and, therefore, harpin proteins may potentially have many valuable agricultural applications. Harpins are characterized by high thermal stability at 100°C. However, it is unknown whether harpins are still active at temperatures above 100°C or whether different temperatures affect the activity of the harpin protein in different ways. The mechanism responsible for the heat stability of harpins is also unknown. Results: We identified a novel harpin, HpaXpm, from the cassava blight bacteria Xanthomonas phaseoli pv. manihotis HNHK. The predicted secondary structure and 3-D structure indicated that the HpaXpm protein has two β-strand domains and two major α-helical domains located at the N-and C-terminal regions, respectively. A phylogenetic tree generated using the maximum likelihood method grouped HpaXpm in clade I of the Hpa1 group along with harpins produced by other Xanthomonas spp. (i.e., HpaG-Xag, HpaG-Xcm, Hpa1-Xac, and Hpa1Xm). Phenotypic assays showed that HpaXpm induced the hypersensitive response (HR), defense responses, and growth promotion in non-host plants more effectively than Hp1Xoo (X. oryzae pv. oryzae). Quantitative realtime PCR analysis indicated that HpaXpm proteins subjected to heat treatments at 100°C, 150°C, or 200°C were still able to stimulate the expression of function-related genes (i.e., the HR marker genes Hin1 and Hsr203J, the defense-related gene NPR1, and the plant growth enhancement-related gene NtEXP6); however, the ability of heattreated HpaXpm to induce HR was different at different temperatures. Conclusions: These findings add a new member to the harpin family. HpaXpm is heat-stable up to 200°C and is able to stimulate powerful beneficial biological functions that could potentially be more valuable for agricultural applications than those stimulated by Hpa1Xoo. We hypothesize that the extreme heat resistance of HpaXpm is because the structure of harpin is very stable and, therefore, the HpaXpm structure is less affected by temperature.

Clostridioides difficile in Calves in Central Italy: Prevalence, Molecular Typing, Antimicrobial Susceptibility and Association with Antibiotic Administration

“…In our study, RT-126, -033, -078 and -010 turned out to be the most common ribotypes, each isolated from more than one farm. This finding is in accordance with what we have reported in calves in Italy [ 17 ] and is consistent with the literature, which indicates that these ribotypes as the most common ones in neonatal calves and piglets in Europe and Asia [ 15 , 24 , 34 , 40 , 41 , 54 , 55 , 56 , 57 , 58 ].…”

“…It is known that calves and piglets are among the predominant animals harboring C. difficile . Newborns in general are characterised by higher prevalence rates since age is a key factor that affects the isolation of C. difficile in animals [ 15 ]. The consumption of contaminated meat, due to the high prevalence of C. difficile in livestock animals (including calves and piglets), represents a potential mechanism for transmission [ 16 ].…”

Natural Photosensitizers in Antimicrobial Photodynamic Therapy

“…The wax moth G. mellonella is another model organism used to identify the efficiency and toxicity of antimicrobial agents and is likewise a preferred model organism for avoiding ethical concerns related to the use of mammals. Huang et al [ 61 ] reported that G. mellonella is a leading infection model organism, especially in the field of PDT against Candida albicans and S. aureus. G. mellonella studies investigate light penetration, and Figueiredo-Godoi et al [ 62 ] found that light is distributed 0.27–2.45 mm below cuticle G. mellonella larvae.…”

The stability of the coiled-coil structure near to N-terminus influence the heat resistance of harpin proteins from Xanthomonas

“…oryzae to alter the formation of CC and found that N-terminal CC region is essential for eliciting HR, but C-terminus is not. In many studies, the ability of harpin proteins to induce HR was determined by the ratio between the size of the necrotic lesion caused by the HR and the injection site [2,34]. Therefore, we mutated the Hpa1 aa residue at the a, b, or d positions to increase or decrease the PFC, and compared the HR activity of wild Hpa1 and Hpa1 mutants after different temperature treatments to determine their heat resistance.…”

“…oryzae (Xoo) [33]; the cassava blight bacteria, X. phaseoli pv. manihotis (Xpm) [34]; and, the bacterial black spot of mango bacteria, X. citri pv. mangiferaeindicae (Xcm) [2].…”