The antifungal plant defensin AhPDF1.1b is a beneficial factor involved in adaptive response to zinc overload when it is expressed in yeast cells

Antimicrobial peptides represent an expanding family of peptides involved in innate immunity of many living organisms. They show an amazing diversity in their sequence, structure, and mechanism of action. Among them, plant defensins are renowned for their antifungal activity but various side activities have also been described. Usually, a new biological role is reported along with the discovery of a new defensin and it is thus not clear if this multifunctionality exists at the family level or at the peptide level. We previously showed that the plant defensin AhPDF1.1b exhibits an unexpected role by conferring zinc tolerance to yeast and plant cells. In this paper, we further explored this activity using different yeast genetic backgrounds: especially the zrc1 mutant and an UPRE-GFP reporter yeast strain. We showed that AhPDF1.1b interferes with adaptive cell response in the endoplasmic reticulum to confer cellular zinc tolerance. We thus highlighted that, depending on its cellular localization, AhPDF1.1b exerts quite separate activities: when it is applied exogenously, it is a toxin against fungal and also root cells, but when it is expressed in yeast cells, it is a peptide that modulates the cellular adaptive response to zinc overload

Effects of antimony and arsenic on antioxidant enzyme activities of two steppic plant species in an old antimony mining area

The present work was undertaken to determine strategies and antioxidant enzyme activities involved in the adaptation of two wild steppic plants (Hedysarum pallidum Desf. and Lygeum spartum L.) to the toxic environment of the abandoned antimony mining area of Djebel Hamimat (Algeria). For this purpose, soils and plants were collected in different zones coinciding with a Sb and As concentrations gradient in the soil. Antimony (Sb) and arsenic (As) were analyzed by ICP-OES in the soils and the aboveground parts and roots of the plants. Malondialdehyde (MDA) and antioxidant enzyme activities were measured by spectrometry. Results show levels of Sb and As exceptionally high in most soil and plant samples. The two species accumulate differently Sb and As in their above and belowground parts. MDA levels, in the two parts of both species, increase significantly with increasing soil Sb and As concentrations, but they are significantly higher in H. pallidum than in L. spartum. The activities of antioxidant enzymes differ significantly according to the soil metalloid concentrations, the plant species considered and the plant part. Apart from superoxide dismutase (SOD) whose activity is, overall, higher in H. pallidum than in L. spartum, the activities of all the other enzymes studied (glutathione S-transferase (GST), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX)) are generally higher in L. spartum than in H. pallidum. For both species, APX and GST are overall more active in the upper parts than in the roots, while it is the reverse for SOD and CAT. POD is more active in the upper parts than in the roots of L. spartum and the reverse applies to H. pallidum. It appears that the two studied plant species use different tolerance strategies to protect themselves against elevated As and Sb concentrations

Effect of Zinc on the Growth and the Antioxidant System of Lens Culinaris Cultivated on Agar Medium

This study aimed to analyze the impact of Zn on the growth and the antioxidant response of Lens culinaris. For this purpose, the seeds were germinated for 6 days in an MS/2 culture medium with different Zn concentrations. Malondialdehyde (MDA), total protein contents, and antioxidant enzymes activities were measured in both parts of the plant by spectrometry. The results showed that from the Zn concentration of 250 µM, the growth of lentils is inversely proportional to the concentration of Zn in the culture medium. The variations in the level of MDA are not very significant, but at 10 000 μM of Zn in the medium, the level becomes very important, whilst the total protein content decreased. Besides, the evaluation of enzymatic activities indicated that the decline of peroxidase (POD) is concomitant with the increase in glutathione peroxidase (GPx) and that glutathione S-transferase (GST), as well as catalase (CAT) reach their maximum activities at 10 000 µM and 3000 µM of Zn in upper parts and roots, respectively. These findings revealed that MDA is a real indicator of oxidative stress in Lens culinaris and that this plant is tolerant to the presence of Zn in the culture medium by developing a powerful antioxidant system, but beyond a certain concentration its antioxidant system becomes ineffective and the plant enters a stress state