An Outlook on the Localisation and Structure-Function Relationships of R Proteins in <Emphasis Type="Italic">Solanum</Emphasis>

The co-evolution of plants and plant-pathogens shaped a multi-layered defence system in plants, in which Resistance proteins (R proteins) play a significant role. A fundamental understanding of the functioning of these R proteins and their position in the broader defence system of the plant is essential. Sub-project 3 of the BIOEXPLOIT programme studies how R proteins are activated upon effector recognition and how recognition is conveyed in resistance signalling pathways, using the solanaceous R proteins Rx1 (from S. tuberosum spp. andigena; conferring extreme resistance against Potato Virus X), I-2 (from S. lycopersicon; mediating resistance to Fusarium oxysporum) and Mi-1.2 (from S. lycopersicon; conferring resistance to Meloidogyne incognita) as model systems. The results obtained in this project will serve as a model for other R proteins and will be translated to potential applications or alternative strategies for disease resistance. These include the modification of the recognition specificity of R proteins with the aim to obtain broad spectrum resistance to major pathogens in potato.     

Carotenoid production by the marine microalgae Nannochloropsis oculata in different low‐cost culture media

Nannochloropsis oculata (Eustigmatophyceae) is a marine microalga of great biotechnological interest, mainly due to its large production of lipids containing polyunsaturated fatty acids. In addition, this species presents a wide range of commercial interest pigments, such as zeaxanthin, beta‐carotene, and other xanthophylls, with potential for several industrial applications. However, most of the research concerning pigment production by N. oculata has been conducted by employing high‐cost laboratorial growth media, which makes large‐scale pigment production using these microalgae impractical. Considering the high interest and commercial value in microalgae pigments, this study investigates the feasibility of producing pigments by N. oculata using five different low‐cost growth media (fertilizers and aquaculture effluents). Nutrient (ammonia, nitrite and phosphate) concentrations, cell abundance, biomass, and the concentration/composition of pigments were measured. The pigment profile of N. oculata showed chlorophyll‐a as the dominant pigment, along with violaxanthin, vaucheraxanthin, and lower concentrations of antheraxanthin, zeaxanthin and beta‐carotene. Although the highest biomass (516.4 ± 76.71 mg/L) and pigment content (0.98 mg/g) were achieved in the laboratory media (f/2), the low‐cost media (containing ammonium sulfate, calcium superphosphate and urea) revealed a great potential for the production of pigments, specially chlorophyll‐a, violaxanthin and zeaxanthin, due to the high pigment content per unit of biomass.     

New Insights on the Terpenome of the Red Seaweed Laurencia dendroidea (Florideophyceae,Rhodophyta)

The red seaweeds belonging to the genus Laurencia are well known as halogenated secondary metabolites producers, mainly terpenoids and acetogennins. Several of these chemicals exhibit important ecological roles and biotechnological applications. However, knowledge regarding the genes involved in the biosynthesis of these compounds is still very limited. We detected 20 different genes involved in the biosynthesis of terpenoid precursors, and 21 different genes coding for terpene synthases that are responsible for the chemical modifications of the terpenoid precursors, resulting in a high diversity of carbon chemical skeletons. In addition, we demonstrate through molecular and cytochemical approaches the occurrence of the mevalonate pathway involved in the biosynthesis of terpenes in L. dendroidea. This is the first report on terpene synthase genes in seaweeds, enabling further studies on possible heterologous biosynthesis of terpenes from L. dendroidea exhibiting ecological or biotechnological interest.     

Evaluation of Macroalgae Sulfated Polysaccharides on the Leishmania (L.) amazonensis Promastigote

The sulfated polysaccharides from Solieria filiformis (Sf), Botryocladia occidentalis (Bo), Caulerpa racemosa (Cr) and Gracilaria caudata (Gc) were extracted and extensively purified. These compounds were then subjected to in vitro assays to evaluate the inhibition of these polysaccharides on the growth of Leishmania (L.) amazonensis promastigotes. Under the same assay conditions, only three of the four sulfated polysaccharides were active against L. amazonensis, and the polysaccharide purified from Cr was the most potent (EC₅₀ value: 34.5 μg/mL). The polysaccharides derived from Bo and Sf demonstrated moderate anti-leishmanial activity (EC₅₀ values of 63.7 μg/mL and 137.4 μg/mL). In addition, we also performed in vitro cytotoxic assays toward peritoneal macrophages and J774 macrophages. For the in vitro cytotoxicity assay employing J774 cells, all of the sulfated polysaccharides decreased cell survival, with CC₅₀ values of 27.3 μg/mL, 49.3 μg/mL, 73.2 μg/mL, and 99.8 μg/mL for Bo, Cr, Gc, and Sf, respectively. However, none of the sulfated polysaccharides reduced the cell growth rate of the peritoneal macrophages. These results suggest that macroalgae contain compounds with various chemical properties that can control specific pathogens. According to our results, the assayed sulfated polysaccharides were able to modulate the growth rate and cell survival of Leishmania (L.) amazonensis promastigotes in in vitro assays, and these effects involved the interaction of the sulfated polysaccharides on the cell membrane of the parasites.     

First isolation of Mycobacterium microti (Llama-type) from a dog

We report the first isolation of Mycobacterium microti from a dog with lesions of acute peritonitis. The isolate was demonstrated to be M. microti of Llama-Type by spoligotyping. Epidemiological implications of the isolation of this possibly zoonotic agent from a dog are discussed.     

Mycobacterium szulgai infection in a captive population of African clawed frogs (Xenopus tropicalis).

A colony of captive Xenopus tropicalis became infected with Mycobacterium szulgai. Clinical signs, when observed, were lethargy, weight loss, and emaciation. Visceral granulomas were common findings at laparoscopy and necropsy. The diagnosis of mycobacteriosis was based on histologic appearance and Ziehl-Neelsen staining of tissues. The identification of M. szulgai organisms was based on comparison of the 16S rRNA gene sequence with several GenBank databases. There have been no reports of this mycobacterial species as the causative agent of naturally occurring disease in amphibians.