New insights into the roles of ethylene and jasmonic acid in the acquisition of selenium resistance in plants.

In a recent paper, we reported that both ethylene and jasmonic acid (JA) are important for selenium (Se) resistance in Arabidopsis. Elevated levels of reactive oxygen species were associated with ethylene and JA production in a Se-resistant Arabidopsis ecotype. Here, we further discuss the functions of these phytohormones, and their possible interactions, in plant Se resistance and -accumulation, placing our data in a broader perspective of other recently published papers

Microbial fructan production in transgenic potato plants and tubers.

Fructans (fructose polymers) derived from plants usually have a very low degree of polymerisation (DP) and this limits the technical application of this versatile carbohydrate polymer. Previously we showed that the expression of bacterial fructosyltransferase genes in transgenic plants results in the accumulation of high molecular weight fructans with a DP of over 25,000. Here we report on our progress in accumulating such high DP fructans in potato plants and tubers. In these plants growth, tuber formation and carbohydrate partitioning were analyzed. Young plants showed no difference in growth between wildtype and fructan-producing (KP) plants. However, at a certain timepoint growth in KP plants is reduced and photosynthate starts to accumulate in source leaves. In these plants no diurnal turnover of starch and sucrose is observed. At harvest, the sink organs (roots, tubers) are reduced in weight. Depending on fructan content the KP tubers display a brown phenotype and yield was reduced. The starch content in the KP tubers is inversely correlated with the fructan level, whereas the sucrose, glucose, fructose and protein levels increase substantially, concomitant with fructan concentration. The cellular location of the fructans was investigated via immunofluorescence using monoclonal antibodies against levan and this showed the presence of fructan located along the cell rim instead of in the expected vacuolar location. It is concluded that fructan accumulation in these plants dramatically affects growth and carbohydrate partitioning and possible solutions for these problems are discussed

Plant Selenium Hyperaccumulation Affects Rhizosphere: Enhanced Species Richness and Altered Species Composition

Little is known about the microbiomes associated with plants with unusual properties, including plants that hyperaccumulate toxic elements such as selenium (Se). Se hyperaccumulators contain up to 1.5% of their dry weight in Se, concentrations shown to affect ecological interactions with herbivores, fungal pathogens and neighboring plants. Hyperaccumulators also enrich their surrounding soil with Se, which may alter the rhizobiome. To investigate whether plant Se affects rhizobacterial diversity and composition, we used a combination of culture-independent and culture-based approaches. Sequencing of 16S rRNA gene amplicons using the Illumina platform revealed that the rhizosphere microbiomes of Se hyperaccumulators were significantly different from nonaccumulators from the same site, with a higher average relative abundance of Pedobacter and Deviosa. Additionally, hyperaccumulators harbored a higher rhizobacterial species richness when compared with nonaccumulators from the same family on the same site. Independent from Se present at the site or in the host plant, the bacterial isolates were extremely resistant to selenate and selenite (up to 200 mM) and could reduce selenite to elemental Se. In conclusion, Se hyperaccumulation does not appear to negatively affect rhizobacterial diversity, and may select for certain taxa in the rhizosphere microbiome. Additionally, Se resistance in hyperaccumulator-associated bacteria and archaea may be widespread and not under selection by the host plant

Prospects for crop production under drought:research priorities and future directions

The efficient use of water supplies requires a systems approach that encompasses all aspects of making water available and its use within society that must recognise global issues. Increasing the efficiency of water use within agricultural systems is an essential priority in many regions including the Mediterranean. This review examines the research priorities, the prospects for crop and soil management and plant breeding and biotechnology that are needed to achieve high stable yield under drought in the Mediterranean. Research must combine the latest genomics resources including quantitative genetics, genomics and biomathematics with an ecophysiological understanding of the interactions between crop plant genotypes and the growing environment to better inform crop improvement

Mutan produced in potato amyloplasts adheres to starch granules

Production of water-insoluble mutan polymers in Kardal potato tubers was investigated after expression of a full-length (Gtf I) and a truncated mutansucrase gene referred to as GtfICAT (Gtf I without glucan-binding domain) from Streptococcus downei. Subsequent effects on starch biosynthesis at the molecular and biochemical levels were studied. Expression of the GtfICAT gene resulted in the adhesion of mutan material on starch granules, which stained red with erythrosine, and which was hydrolysed by exo-mutanase. In addition, GtfICAT-expressing plants exhibited a severely altered tuber phenotype and starch granule morphology in comparison to those expressing the full-length Gtf I gene. In spite of that, no structural changes at the starch level were observed. Expression levels of the sucrose- regulated, AGPase and GBSSI genes were down-regulated in only the GTFICAT transformants, showing that GtfICAT expression interfered with the starch biosynthetic pathway. In accordance with the down-regulated AGPase gene, a lower starch content was observed in the GTFICAT transformants. Finally, the rheological properties of the GTFICAT starches were modified; they showed a higher retrogradation during cooling of the starch paste