Metallothioneins (MTs) and phytochelatins (PCs) are small Cys-rich proteins with low molecular mass responsible for detoxifying heavy metals in cells. Arabidopsis thaliana expresses eight metallothionein genes and two types of PCS; however, there is still a need to acquire more knowledge regarding their individual responses to some heavy metals. Thus, it was intended to study the expression of AtMT- and AtPCS1-encoding genes in response to high levels of nickel in wild-type A. thaliana. Seeds of A. thaliana were placed in MS medium supplemented with increasing concentrations of Ni—0 mg L⁻¹, 2.5 mg L⁻¹, 5 mg L⁻¹, 7.5 mg L⁻¹, and 10 mg L⁻¹. After 21 days of exposure, the expression of the AtMTs (1A, 1B, 1C, 2A, 2B, and 3) and AtPCS1 was analysed through RT-qPCR in different plant organs: roots, young leaves, and mature leaves. The concentrations of photosynthetic pigments, hydrogen peroxide, and reduced glutathione were also evaluated, but no significant changes were observed. The gene expression analysis showed that the seven genes reacted differentially to the varying concentrations of Ni and in an organ-specific way. It was noted that in roots, the expression of AtMT1A, AtMT1C, and AtMT3 increased starting with the 2.5 mg L⁻¹ treatment. At the same time, the response in the leaves fluctuated more as AtMT1B and AtMT1C increased in young leaves with concentrations higher than 7.5 and 2.5 mg L⁻¹, respectively, with the remaining genes analysed having their expressions decreased starting with 7.5 mg L⁻¹ of Ni. In mature leaves, AtMT1A increased, while AtMT2A, AtMT2B, and AtPCS1 decreased with Ni concentrations starting from 7.5 mg L⁻¹. These results strongly suggest that the increase in the expression of AtMT1B, AtMT1C, and AtMT3 in the roots significantly reduced Ni toxicity, contributing to its local accumulation and buffering its translocation to the shoots. The overall reduction in the expression of MTs and PCS1 in leaves may be linked to the active participation of MT1A in mature leaves, while young leaves depended on the increased production of MT1B and MT1C to deal with the high amount of Ni present therein. These results contribute further knowledge to the understanding of the defence mechanisms of plants against high levels of Ni regarding the participation of MTs and PCS1.

The endosymbiotic bacteria that live within the body of insects are involved in many aspects of the host physiology, including reproduction and defense. Thus, the exploitation of these microorganisms may have practical applications for the management of vector-borne diseases. In the Mediterranean area, Philaenus spumarius was identified as the main vector of Xylella fastidiosa. This xylem-restricted bacterium is responsible for several diseases in a variety of agricultural crops of high importance, for which there are not any effective control methods. Thus, in this work we evaluate different media types for the isolation and growth of bacteria living within P. spumarius adults, for their potential exploitation in the management of X. fastidiosa. Specifically, we compared the effect of minimal (Luria Bertani—LB) and complex (Modified Melin-Norkrans—MMN) media, with and without fetal bovine or gelling agents, on the number and diversity of bacteria. The collection of isolates obtained was further genetically characterized by repetitive element–based PCR method (BOX-PCR) and sequencing of the 16S ribosomal RNA (rRNA) gene. The results showed no significant differences in the abundance and diversity of bacteria among the two media tested (LB and MMN). The addition of fetal bovine to the media leads to a slight increase in bacterial abundance, in particular in MMN medium. While the liquid media led to a significant increase in abundance, the solid media facilitated the growth of more diverse bacterial taxa. The comparison between BOX-PCR and 16S rRNA gene sequencing for the analysis of 57 bacterial isolates revealed a greater discriminatory power of the former, allowing the differentiation of the bacteria even at the intra-species level. The clustering of the isolates using BOX-PCR fingerprinting was different to that obtained from the 16S rRNA gene phylogenetic tree. The 16S rRNA gene sequencing method proved to be more suitable in phylogenetic evaluations, generally grouping isolates belonging to the same genus.