Habitat is more important than climate for structuring soil fungal communities associated in truffle sites.

The ectomycorrhizal fungi Tuber melanosporum Vittad. and Tuber aestivum Vittad. produce highly valuable truffles, but little is known about the soil fungal communities associated with these truffle species in places where they co-occur. Here, we compared soil fungal communities present in wild and planted truffle sites, in which T. melanosporum and T. aestivum coexist, in Mediterranean and temperate regions over three sampling seasons spanning from 2018 to 2019. We showed that soil fungal community composition and ectomycorrhizal species composition are driven by habitat type rather than climate regions. Also, we observed the influence of soil pH, organic matter content and C:N ratio structuring total and ectomycorrhizal fungal assemblages. Soil fungal communities in wild sites revealed more compositional variability than those of plantations. Greater soil fungal diversity was found in temperate compared to Mediterranean sites when considering all fungal guilds. Ectomycorrhizal diversity was significantly higher in wild sites compared to plantations. Greater mould abundance at wild sites than those on plantation was observed while tree species and seasonal effects were not significant predictors in fungal community structure. Our results suggested a strong influence of both ecosystem age and management on the fungal taxa composition in truffle habitats.

Silvicultural management and altitude prevail on soil properties and fungal community in shaping understorey plant communities in a Mediterranean pine forest.

Understorey vegetation plays a key role in Mediterranean forest ecosystem functioning. However, we still lack a thorough understanding of the patterns and drivers of understorey composition and diversity. As a result, understoreys are often ignored during assessments of forest functioning under climate change. Here we studied the effect of silvicultural management, topography, soil fungal community composition and soil physical and chemical properties on understorey community composition and diversity. The plant cover and number of individuals of understorey perennial plants, shrubs and non-dominant trees was recorded on 24 plots (paired: control-thinned) in a Mediterranean pine-dominated mountainous area in Northeast Spain. The study area represented a broad thinning intensity gradient (from 0 to 70 % in removed stand basal area) along a 400-m altitudinal range (from 609 m to 1013 m). Our results showed that thinning intensity and topography explained the greatest proportion of the total variance in the understorey species composition, i.e., 18 % and 16 %, respectively. Interestingly, the effects of the silvicultural treatments were significant only when considering the altitudinal effect, so that, the main impacts of thinning on the understorey community composition occurred at low altitudes (between 609 m and 870 m). Moreover, we found a significant decrease in both richness and abundance of understorey species in both the control and thinned plots with increasing altitude, with thinned plots being significantly richer in species compared to the control plots. The difference in the understorey community sensitivity to forest thinning along the altitudinal gradient suggests changes in factors that limit plant growth. Low elevation plots were restrained by light availability while high altitudes plots limited by winter freezing temperature.

The potential impact of plant biotechnology on the Millennium Development Goals.

The eight Millennium Development Goals (MDGs) are international development targets for the year 2015 that aim to achieve relative improvements in the standards of health, socioeconomic status and education in the world's poorest countries. Many of the challenges addressed by the MDGs reflect the direct or indirect consequences of subsistence agriculture in the developing world, and hence, plant biotechnology has an important role to play in helping to achieve MDG targets. In this opinion article, we discuss each of the MDGs in turn, provide examples to show how plant biotechnology may be able to accelerate progress towards the stated MDG objectives, and offer our opinion on the likelihood of such technology being implemented. In combination with other strategies, plant biotechnology can make a contribution towards sustainable development in the future although the extent to which progress can be made in today's political climate depends on how we deal with current barriers to adoption.

Promoter diversity in multigene transformation.

Multigene transformation (MGT) is becoming routine in plant biotechnology as researchers seek to generate more complex and ambitious phenotypes in transgenic plants. Every nuclear transgene requires its own promoter, so when coordinated expression is required, the introduction of multiple genes leads inevitably to two opposing strategies: different promoters may be used for each transgene, or the same promoter may be used over and over again. In the former case, there may be a shortage of different promoters with matching activities, but repetitious promoter use may in some cases have a negative impact on transgene stability and expression. Using illustrative case studies, we discuss promoter deployment strategies in transgenic plants that increase the likelihood of successful and stable multiple transgene expression.

The contribution of transgenic plants to better health through improved nutrition: opportunities and constraints.

Malnutrition is a prevalent and entrenched global socioeconomic challenge that reflects the combined impact of poverty, poor access to food, inefficient food distribution infrastructure, and an over-reliance on subsistence mono-agriculture. The dependence on staple cereals lacking many essential nutrients means that malnutrition is endemic in developing countries. Most individuals lack diverse diets and are therefore exposed to nutrient deficiencies. Plant biotechnology could play a major role in combating malnutrition through the engineering of nutritionally enhanced crops. In this article, we discuss different approaches that can enhance the nutritional content of staple crops by genetic engineering (GE) as well as the functionality and safety assessments required before nutritionally enhanced GE crops can be deployed in the field. We also consider major constraints that hinder the adoption of GE technology at different levels and suggest policies that could be adopted to accelerate the deployment of nutritionally enhanced GE crops within a multicomponent strategy to combat malnutrition.

Diffusion of anionic and neutral GFP derivatives through plasmodesmata in epidermal cells of Nicotiana benthamiana.

Plasmodesmata (Pd) are trans-wall membrane channels that permit cell-to-cell transport of metabolites and other small molecules, proteins, RNAs, and signaling molecules. The transport of cytoplasmic soluble macromolecules is a function of the electrochemical gradient between adjacent cells, the number of Pd per interface between adjacent cells, Stokes radius (R(S)), area of the cytoplasmic annulus, and channel length. The size of the largest molecule that can pass through Pd defines the Pd size exclusion limit. However, since the shape and size of a molecule determines its capacity to diffuse through pores or tubes, R(S) is a better measure. Relatively small changes in R(S) can cause large differences in the mobility of molecular probes, particularly if the pore size is close to that of the probe. In addition, as the dimensions of a macromolecule approach that of the channel, membrane charge effects may become important. We employed quantitative tools and molecular modeling to measure the apparent coefficient of conductivity of Pd, C(Pd), for the non-targeted transport of macromolecules. This method allowed us to examine the influence of protein charge and R(S) on C(Pd) in Nicotiana benthamiana. The C(Pd) of modified green fluorescent proteins (GFPs) of different sizes but with the same charge as native GFP and of a more negatively charged derivative were determined. We found that the C(Pd) of cytoplasmic soluble GFP and cytoplasmic forms of modified GFP were the most strongly correlated with R(S) and that the apparent aberrant increase in C(Pd) of a negatively charged GFP derivative was, at least in part, the result of the charge effect on R(S).