ESCRT-I Mediates FLS2 Endosomal Sorting and Plant Immunity

The plant immune receptor FLAGELLIN SENSING 2 (FLS2) is present at the plasma membrane and is internalized following activation of its ligand flagellin (flg22). We show that ENDOSOMAL SORTING COMPLEX REQUIRED FOR TRANSPORT (ESCRT)-I subunits play roles in FLS2 endocytosis in Arabidopsis. VPS37-1 co-localizes with FLS2 at endosomes and immunoprecipitates with the receptor upon flg22 elicitation. Vps37-1 mutants are reduced in flg22-induced FLS2 endosomes but not in endosomes labeled by Rab5 GTPases suggesting a defect in FLS2 trafficking rather than formation of endosomes. FLS2 localizes to the lumen of multivesicular bodies, but this is altered in vps37-1 mutants indicating compromised endosomal sorting of FLS2 by ESCRT-I loss-of-function. VPS37-1 and VPS28-2 are critical for immunity against bacterial infection through a role in stomatal closure. Our findings identify that VPS37-1, and likewise VPS28-2, regulate late FLS2 endosomal sorting and reveals that ESCRT-I is critical for flg22-activated stomatal defenses involved in plant immunity.     

Diurnal patterns of growth and transient reserves of sink and source tissues are affected by cold nights in barley

Barley is described to mostly use sucrose for night carbon requirements. To understand how the transient carbon is accumulated and utilized in response to cold, barley plants were grown in a combination of cold days and/or nights. Both daytime and night cold reduced growth. Sucrose was the main carbohydrate supplying growth at night, representing 50–60% of the carbon consumed. Under warm days and nights, starch was the second contributor with 26% and malate the third with 15%. Under cold nights, the contribution of starch was severely reduced, due to an inhibition of its synthesis, including under warm days, and malate was the second contributor to C requirements with 24–28% of the total amount of carbon consumed. We propose that malate plays a critical role as an alternative carbon source to sucrose and starch in barley. Hexoses, malate, and sucrose mobilization and starch accumulation were affected in barley elf3 clock mutants, suggesting a clock regulation of their metabolism, without affecting growth and photosynthesis however. Altogether, our data suggest that the mobilization of sucrose and malate and/or barley growth machinery are sensitive to cold.     

Characterisation of a novel Emaravirus identified in mosaic-diseased Eurasian aspen (Populus tremula)

Since Emaraviruses have been discovered in 2007 several new species were detected in a range of host plants. Five genome segments of a novel Emaravirus from mosaic-diseased Eurasian aspen (Populus tremula) have been completely determined. The monocistronic, segmented ssRNA genome of the virus shows a genome organisation typical for Emaraviruses encoding the viral RNA-dependent RNA polymerase (RdRP, 268.2 kDa) on RNA1 (7.1 kb), a glycoprotein precursor (GPP, 73.5 kDa) on RNA2 (2.3 kb), the viral nucleocapsid protein (N, 35.6 kDa) on RNA3 (1.6 kb), and a putative movement protein (MP, 41.0 kDa) on RNA4 (1.6 kb). The fifth identified genome segment (RNA5, 1.3 kb) encodes a protein of unknown function (P28, 28.1 kDa). We discovered that it is distantly related to proteins encoded by Emaraviruses, such as P4 of European mountain ash ringspot-associated virus. All proteins from this group contain a central hydrophobic region with a conserved secondary structure and a hydrophobic amino acid stretch, bordered by two highly conserved positions, thus clearly representing a new group of homologues of Emaraviruses. The virus identified in Eurasian aspen is closely associated with observed leaf symptoms, such as mottle, yellow blotching, variegation and chloroses along veins. All five viral RNAs were regularly detectable by RT-PCR in mosaic-diseased P. tremula in Norway, Finland and Sweden (Fennoscandia). Observed symptoms and testing of mosaic-diseased Eurasian aspen by virus-specific RT-PCR targeting RNA3 and RNA4 confirmed a wide geographic distribution of the virus in Fennoscandia. We could demonstrate that the mosaic-disease is graft-transmissible and confirmed that the virus is the causal agent by detection in symptomatic, graft-inoculated seedlings used as rootstocks as well as in the virus-infected scions used for graft-inoculation. Owing to these characteristics, the virus represents a novel species within the genus Emaravirus and was tentatively denominated aspen mosaic-associated virus.     

Loss of interleukin-10 exacerbates early Type-1 diabetes-induced bone loss

Type-1 diabetes (T1D) increases systemic inflammation, bone loss, and risk for bone fractures. Levels of the anti-inflammatory cytokine interleukin-10 (IL-10) are decreased in T1D, however their role in T1D-induced osteoporosis is unknown. To address this, diabetes was induced in male IL-10 knockout (KO) and wild-type (WT) mice. Analyses of femur and vertebral trabecular bone volume fraction identified bone loss in T1D-WT mice at 4 and 12 weeks, which in T1D-IL-10-KO mice was further reduced at 4 weeks but not 12 weeks. IL-10 deficiency also increased the negative effects of T1D on cortical bone. Osteoblast marker osterix was decreased, while osteoclast markers were unchanged, suggesting that IL-10 promotes anabolic processes. MC3T3-E1 osteoblasts cultured under high glucose conditions displayed a decrease in osterix which was prevented by addition of IL-10. Taken together, our results suggest that IL-10 is important for promoting osteoblast maturation and reducing bone loss during early stages of T1D.     

Mathematical model of fructan biosynthesis and polymer length distribution in plants

Background and Aims

There are many unresolved issues concerning the biochemistry of fructan biosynthesis. The aim of this paper is to address some of these by means of modelling mathematically the biochemical processes.

Methods

A model has been constructed for the step-by-step synthesis of fructan polymers. This is run until a steady state is achieved for which a polymer distribution is predicted. It is shown how qualitatively different distributions can be obtained.

Key Results

It is demonstrated how a set of experimental results on polymer distribution can by simulated by a simple parameter adjustments.

Conclusions

Mathematical modelling of fructan biosynthesis can provide a useful tool for helping elucidate the details of the biosynthetic processes.     

Avoidance conditioning in bamboo sharks (Chiloscyllium griseum and C. punctatum): behavioral and neuroanatomical aspects

Animals face different threats; to survive, they have to anticipate how to react or how to avoid these. It has already been shown in teleosts that selected regions in the telencephalon, i.e., the medial pallium, are involved in avoidance learning strategies. No such study exists for any chondrichthyan. In nature, an avoidance reaction may vary, ranging from a ‘freeze’ reaction to a startling response and quick escape. This study investigated whether elasmobranchs (Chiloscyllium griseum and C. punctatum) can be conditioned in an aversive classical conditioning paradigm. Upon successful conditioning, the dorsal, medial and lateral pallium were removed (group 1) and performance tested again. In a second group, the same operation was performed prior to training. While conditioning was successful in individuals of both groups, no escape responses were observed. Post-operative performance was assessed and compared between individual and groups to reveal if the neural substrates governing avoidance behavior or tasks learned in a classical conditioning paradigm are located within the telencephalon, as has been shown for teleosts such as goldfish.     

Physical mapping and cloning of RAD56

Here we report the physical mapping of the rad56-1 mutation to the NAT3 gene, which encodes the catalytic subunit of the NatB N-terminal acetyltransferase in Saccharomyces cerevisiae. Mutation of RAD56 causes sensitivity to X-rays, methyl methanesulfonate, zeocin, camptothecin and hydroxyurea, but not to UV light, suggesting that N-terminal acetylation of specific DNA repair proteins is important for efficient DNA repair.