Pluripotency of Arabidopsis xylem pericycle underlies shoot regeneration from root and hypocotyl explants grown in vitro

We have established a detailed framework for the process of shoot regeneration from Arabidopsis root and hypocotyl explants grown in vitro . Using transgenic plant lines in which the GUS or GFP genes were fused to promoters of developmental genes ( WUS , CLV1 , CLV3 , STM , CUC1 , PLT1 , RCH1 , QC25 ), or to promoters of genes encoding indicators of the auxin response ( DR5 ) or transport ( PIN1 ), cytokinin (CK) response ( ARR5 ) or synthesis ( IPT5 ), or mitotic activity ( CYCB1 ), we showed that regenerated shoots originated directly or indirectly from the pericycle cells adjacent to xylem poles. In addition, shoot regeneration appeared to be partly similar to the formation of lateral root meristems (LRMs). During pre-culture on a 2, 4-dichlorophenoxyacetic acid (2, 4-D)-rich callus-inducing medium (CIM), xylem pericycle reactivation established outgrowths that were not true calli but had many characteristics of LRMs. Transfer to a CK-rich shoot-inducing medium (SIM) resulted in early LRM-like primordia changing to shoot meristems. Direct origin of shoots from the xylem pericycle occurred upon direct culture on CK-containing media without prior growth on CIM. Thus, it appeared that the xylem pericycle is more pluripotent than previously thought. This pluripotency was accompanied by the ability of pericycle derivatives to retain diploidy, even after several rounds of cell division. In contrast, the phloem pericycle did not display such developmental plasticity, and responded to CKs with only periclinal divisions. Such observations reinforce the view that the pericycle is an 'extended meristem' that comprises two types of cell populations. They also suggest that the founder cells for LRM initiation are not initially fully specified for this developmental pathway.     

3D strain map of axially loaded mouse tibia: a numerical analysis validated by experimental measurements

A combined experimental/numerical study was performed to calculate the 3D octahedral shear strain map in a mouse tibia loaded axially. This study is motivated by the fact that the bone remodelling analysis, in this in vivo mouse model should be performed at the zone of highest mechanical stimulus to maximise the measured effects. Accordingly, it is proposed that quantification of bone remodelling should be performed at the tibial crest and at the distal diaphysis. The numerical model could also be used to furnish a more subtle analysis as a precise correlation between local strain and local biological response can be obtained with the experimentally validated numerical model.     

Interleukin-33 Is Biologically Active Independently of Caspase-1 Cleavage

The new interleukin (IL)-1 family cytokine IL-33 is synthesized as a 30-kDa precursor. Like pro-IL-1β, human pro-IL-33 was reported to be cleaved by caspase-1 to generate an 18-kDa fragment, which is sufficient to activate signaling by the IL-33 receptor T1/ST2. However, the proposed caspase-1 cleavage site is poorly conserved between species. In addition, it is not clear whether caspase-1 cleavage of pro-IL-33 occurs in vivo and whether, as for IL-1β, this cleavage is a prerequisite for IL-33 secretion and bioactivity. In this study, we further investigated caspase-1 cleavage of mouse and human pro-IL-33 and assessed the potential bioactivity of the IL-33 precursor. We observed the generation of a 20-kDa IL-33 fragment in cell lysates, which was enhanced by incubation with caspase-1. However, in vitro assays of mouse and human pro-IL-33 indicated that IL-33 is not a direct substrate for this enzyme. Consistently, caspase-1 activation in THP-1 cells induced cleavage of pro-IL-1β but not of pro-IL-33, and activated THP-1 cells released full-length pro-IL-33 into culture supernatants. Finally, addition of full-length pro-IL-33 induced T1/ST2-dependent IL-6 secretion in mast cells. However, we observed in situ processing of pro-IL-33 in mast cell cultures, and it remains to be determined whether full-length pro-IL-33 itself indeed represents the bioactive species. In conclusion, our data indicate that pro-IL-33 is not a direct substrate for caspase-1. In addition, our results clearly show that caspase-1 cleavage is not required for pro-IL-33 secretion and bioactivity, highlighting major differences between IL-1β and IL-33.Interleukin (IL)² -33, the most recently described cytokine of the IL-1 family, is synthesized as a 30-kDa precursor. Human pro-IL-33, like pro-IL-1β, was reported to be cleaved by caspase-1 in vitro to generate an 18-kDa fragment, termed mature IL-33, which is sufficient to activate signaling by the IL-33 receptor T1/ST2 (1).Caspase-1 is an endoproteinase that specifically cleaves Asp-Xaa bonds, where Xaa typically refers to a small, often hydrophobic residue (2–4). Caspase-1 activity absolutely requires the presence of an Asp residue at position −1 of the cleavage site. Consistently, replacement of Asp¹¹⁶ by other amino acids, such as Ala, was previously demonstrated to prevent caspase-1 cleavage of pro-IL-1β (2). Recombinant (r) mature IL-33 starts at Ser¹¹² for human (h) IL-33 and at Ser¹⁰⁹ for mouse (m) IL-33, neither of which corresponds exactly to the position of a potential caspase-1 cleavage site. Indeed, the N-terminal moiety of human pro-IL-33 sequence contains a single Asp at position 110, and the N-terminal portion of mouse pro-IL-33 contains an Asp at positions 88 and 106. In fact, the region located between amino acids 80 and 110 of pro-IL-33 is rather poorly conserved between species (5). In particular, no Asp residues can be consistently found at an identical position across species to hint at the presence of a conserved caspase-1 cleavage site. So far, caspase-1 cleavage of pro-IL-33 has not been investigated in any species other than human.Expression of endogenous IL-33 has been described most extensively in endothelial cells, where essentially nuclear, full-length 30-kDa pro-IL-33 is detected (5–7). To date, only two studies have examined potential effects of caspase-1 activation on the processing and secretion of pro-IL-33 in living cells. In one study, stimulation of murine glial cultures with caspase-1 activators induced secretion of bioactive IL-33 into culture supernatants, but the size of the secreted protein was not assessed (8). It is thus not clear whether caspase-1 cleavage of pro-IL-33 occurs in mouse cells. In a second study, Western blot analysis revealed the presence of a 32-kDa protein and minor 17 and 20 kDa bands reacting with anti-IL-33 antibodies in the supernatants of THP-1 cells upon caspase-1 activation, suggesting secretion of full-length pro-IL-33 and of two potential cleavage products (9). Although this last observation suggests that some pro-IL-33 may be secreted, it not known to what extent IL-33 secretion is dependent on caspase-1 cleavage. Finally, so far all studies reporting T1/ST2-mediated effects of IL-33 were performed using the recombinant mature form of IL-33, whereas potential biological activity of the full-length precursor form has not been tested. It thus remains to be shown whether, as for IL-1β, caspase-1 cleavage is indeed required for IL-33 bioactivity. In the present study, we thus further investigated caspase-1 cleavage of mouse and human pro-IL-33 in vitro and in cultured cells and assessed the potential bioactivity of the IL-33 precursor.     

Differentiated influence of off-road and on-road cycling practice on balance control and the related-neurosensory organization

This study aimed to determine the sensorimotor strategies privileged by mountain bikers (MTB) and road cyclists (RC) for balance control. Twenty-four MTB and 24 RC (off-road Olympics, world, continental and national champions, Tour-de-France participants, on-road world cup race winner) volunteered to answer a questionnaire about the characteristics of cycling practice and perform a sensory organization test, aiming to evaluate balance control in 6 different sensory situations based upon visual and support surface perturbations (C1^ES to C6^ES). RC balance performances were better than those of MTB both during quiet stance eyes opened (C1^ES, p = 0.011) and when only somatosensory information is disrupted (C4^ES, p = 0.039), highlighting a higher use of vision to control balance in RC. Moreover, a positive correlation was shown in the whole population (MTB + RC) between the visual ratio (R^VIS = C4^ES/C1^ES) and the proportion of riding distance of on-road cycling (ρ = 0.28, p = 0.054). In MTB, the use of proprioception (somatosensory ratio: R^SOM = C2^{ES(eyes closed)}/C1^ES) was increased by a higher intensity of off-road cycling (ρ = 0.49, p = 0.018) and that of vision (R^VIS) by a higher intensity of on-road cycling (ρ = 0.41, p = 0.048). The difference in sensory organization between MTB and RC could be explained by adaptive processes elaborated from environmental stimulations and technical specificities of these disciplines.     

ADAM function in embryogenesis

Cleavage of proteins inserted into the plasma membrane (shedding) is an essential process controlling many biological functions including cell signaling, cell adhesion and migration as well as proliferation and differentiation. ADAM surface metalloproteases have been shown to play an essential role in these processes. Gene inactivation during embryonic development have provided evidence of the central role of ADAM proteins in nematodes, flies, frogs, birds and mammals. The relative contribution of four subfamilies of ADAM proteins to developmental processes is the focus of this review.     

Post-release survey to assess impact and potential host range expansion by Amitus hesperidum and Encarsia perplexa, two parasitoids introduced for the biological control of the citrus blackfly, Aleurocanthus woglumi in Dominica

Four years after the release of two exotic parasitoids, Amitus hesperidum Silvestri (Hymenoptera: Platygasteridae) and Encarsia perplexa Huang and Polaszek (Hymenoptera: Aphelinidae) for the classical biological control of the citrus blackfly (CBF), Aleurocanthus woglumi Ashby (Hemiptera: Aleyrodidae) in Dominica, a survey was conducted to assess establishment as well as potential nontarget effects especially on Aleyrodidae and other related taxa. CBF populations were low to non-existent in 50 of 51 field sites examined. At the site where CBF was encountered, both E. perplexa and A. hesperidum were present and CBF populations were declining. The two parasitoids were not among the several species collected on nontarget Aleryodidae and Hemiptera. It is concluded that E. perplexa and A. hesperidum have kept CBF populations under effective biological control in Dominica and there is no evidence of any nontarget effects on other Aleyrodidae or their natural enemies. Handling Editor: Dirk Babendreier.     

Deficiency of Dol-P-Man Synthase Subunit DPM3 Bridges the Congenital Disorders of Glycosylation with the Dystroglycanopathies

Alpha-dystroglycanopathies such as Walker Warburg syndrome represent an important subgroup of the muscular dystrophies that have been related to defective O-mannosylation of alpha-dystroglycan. In many patients, the underlying genetic etiology remains unsolved. Isolated muscular dystrophy has not been described in the congenital disorders of glycosylation (CDG) caused by N-linked protein glycosylation defects. Here, we present a genetic N-glycosylation disorder with muscular dystrophy in the group of CDG type I. Extensive biochemical investigations revealed a strongly reduced dolichol-phosphate-mannose (Dol-P-Man) synthase activity. Sequencing of the three DPM subunits and complementation of DPM3-deficient CHO2.38 cells showed a pathogenic p.L85S missense mutation in the strongly conserved coiled-coil domain of DPM3 that tethers catalytic DPM1 to the ER membrane. Cotransfection experiments in CHO cells showed a reduced binding capacity of DPM3(L85S) for DPM1. Investigation of the four Dol-P-Man-dependent glycosylation pathways in the ER revealed strongly reduced O-mannosylation of alpha-dystroglycan in a muscle biopsy, thereby explaining the clinical phenotype of muscular dystrophy. This mild Dol-P-Man biosynthesis defect due to DPM3 mutations is a cause for alpha-dystroglycanopathy, thereby bridging the congenital disorders of glycosylation with the dystroglycanopathies.     

mtDNA and Y-chromosome variation in the Talysh of Iran and Azerbaijan

The Northern Talysh from Azerbaijan and the Southern Talysh from Iran self‐identify as one ethnic group and speak a Northwestern Iranian language. However, the Northern and Southern Talysh dialects are so different that they may actually be separate languages. Does this linguistic differentiation reflect internal change due to isolation, or could contact‐induced change have played a role? We analyzed mtDNA HVI sequences, 11 Y‐chromosome bi‐allelic markers, and 9 Y‐STR loci in Northern and Southern Talysh and compared them with their neighboring groups. The mtDNA data show a close relatedness of both groups with each other and with neighboring groups, whereas the Northern Talysh Y‐chromosome variation differs from that of neighboring groups, probably as a result of genetic drift. This genetic drift most likely reflects a founder event in the male gene pool of Northern Talysh: either fewer males than females migrated to Azerbaijan, or there was a higher degree of relatedness among the male migrants. Since we find no evidence of substantial genetic contact between either Northern or Southern Talysh and neighboring groups, we conclude that internal change, rather than contact‐induced change, most likely explains the linguistic differentiation between Northern and Southern Talysh. Am J Phys Anthropol, 2009. © 2008 Wiley‐Liss, Inc.     

Impact of environmental stress on aphid clonal resistance to parasitoids: Role of Hamiltonella defensa bacterial symbiosis in association with a new facultative symbiont of the pea aphid

Resistance to endoparasitoids in aphids involves complex interactions between insect and microbial players. It is now generally accepted that the facultative bacterial symbiont Hamiltonella defensa of the pea aphid Acyrthosiphon pisum is implicated in its resistance to the parasitoid Aphidius ervi. It has also been shown that heat negatively affects pea aphid resistance, suggesting the thermosensitivity of its defensive symbiosis. Here we examined the effects of heat and UV-B on the resistance of A. pisum to A. ervi and we relate its stability under heat stress to different facultative bacterial symbionts hosted by the aphid. For six A. pisum clones harboring four different facultative symbiont associations, the impact of heat and UV-B was measured on their ability to resist A. ervi parasitism under controlled conditions. The results revealed that temperature strongly affected resistance, while UV-B did not. As previously shown, highly resistant A. pisum clones singly infected with H. defensa became more susceptible to parasitism after exposure to heat. Interestingly, clones that were superinfected with H. defensa in association with a newly discovered facultative symbiont, referred to as PAXS (pea aphid X-type symbiont), not only remained highly resistant under heat stress, but also expressed previously unknown, very precocious resistance to A. ervi compared to clones with H. defensa alone. The prevalence of dual symbiosis involving PAXS and H. defensa in local aphid populations suggests its importance in protecting aphid immunity to parasitoids under abiotic stress.