Fusion Proteins and Select Lipids Cooperate as Membrane Receptors for the Soluble N-Ethylmaleimide-sensitive Factor Attachment Protein Receptor (SNARE) Vam7p

Vam7p, the vacuolar soluble Q_c-SNARE, is essential for yeast vacuole fusion. The large tethering complex, homotypic fusion and vacuole protein sorting complex (HOPS), and phosphoinositides, which interact with the Vam7p PX domain, have each been proposed to serve as its membrane receptors. Studies with the isolated organelle cannot determine whether these receptor elements suffice and whether ligands or mutations act directly or indirectly on Vam7p binding to the membrane. Using pure components that are active in reconstituted vacuolar fusion, we now find that Vam7p binds to membranes through its combined affinities for several vacuolar membrane constituents: HOPS, phosphatidylinositol 3-phosphate, SNAREs, and acidic phospholipids. Acidic lipids allow low concentrations of Vam7p to suffice for fusion; without acidic lipids, the block to fusion is partially bypassed by high concentrations of Vam7p.     

Malonate Catabolism Does Not Drive N2 Fixation in Legume Nodules

Malonyl-coenzyme A (CoA) decarboxylase, malonyl-CoA synthetase, and malonate transporter mutants of Rhizobium leguminosarum bv. viciae and trifolii fixed N₂ at wild-type rates on pea and clover, respectively. Thus, malonate does not drive N₂ fixation in legume nodules.     

Cloning and sequencing of partial DNA-A of Cassava mosaic virus

Abstract

Polymerase chain reaction of Cassava mosaic virus revealed that out of the 50 samples analysed only two samples, one from Musiri (Trichy district) and other from Mallur (Salem district), were detected with ICMV infection as 904 bp fragment of DNA-A amplified. All the other samples from various districts of Tamil Nadu were detected invariably with SLCMV as they amplified 599 bp of DNA-A. A 599 bp fragment of DAN-A was cloned and sequenced from the sample collected from Mallur. The nucleotide sequence has been submitted to GenBank under the accession number DQ303479. The nucleotide sequence was compared with other cassava infecting geminiviruses and other geminiviruses in GenBank. Cluster dendrogram revealed that the cloned sequence was most closely related to ICMV, Maharastra strain rather than SLCMV, forming one cluster. Comparative sequence analyses showed that the cloned fragment shared a maximum sequence identity with ICMV at nucleotide levels (93%) than with SLCMV (88%).     

Macaque Monkeys Perceive the Flash Lag Illusion

Transmission of neural signals in the brain takes time due to the slow biological mechanisms that mediate it. During such delays, the position of moving objects can change substantially. The brain could use statistical regularities in the natural world to compensate neural delays and represent moving stimuli closer to real time. This possibility has been explored in the context of the flash lag illusion, where a briefly flashed stimulus in alignment with a moving one appears to lag behind the moving stimulus. Despite numerous psychophysical studies, the neural mechanisms underlying the flash lag illusion remain poorly understood, partly because it has never been studied electrophysiologically in behaving animals. Macaques are a prime model for such studies, but it is unknown if they perceive the illusion. By training monkeys to report their percepts unbiased by reward, we show that they indeed perceive the illusion qualitatively similar to humans. Importantly, the magnitude of the illusion is smaller in monkeys than in humans, but it increases linearly with the speed of the moving stimulus in both species. These results provide further evidence for the similarity of sensory information processing in macaques and humans and pave the way for detailed neurophysiological investigations of the flash lag illusion in behaving macaques.     

“Biofilmology”: a multidisciplinary review of the study of microbial biofilms

The observation of biofilm formation is not a new phenomenon. The prevalence and significance of biofilm and aggregate formation in various processes have encouraged extensive research in this field for more than 40 years. In this review, we highlight techniques from different disciplines that have been used to successfully describe the extracellular, surface and intracellular elements that are predominant in understanding biofilm formation. To reduce the complexities involved in studying biofilms, researchers in the past have generally taken a parts-based, disciplinary specific approach to understand the different components of biofilms in isolation from one another. Recently, a few studies have looked into combining the different techniques to achieve a more holistic understanding of biofilms, yet this approach is still in its infancy. In order to attain a global understanding of the processes involved in the formation of biofilms and to formulate effective biofilm control strategies, researchers in the next decade should recognise that the study of biofilms, i.e. biofilmology, has evolved into a discipline in its own right and that mutual cooperation between the various disciplines towards a multidisciplinary research vision is vital in this field.     

Molecular structures of nickel(II) monochelates of a racemic tridentate ligand and co-ligand induced structural variations

Using a racemic mixture of the tridentate ligand, (((2-pyridyl)ethylamine)methyl)phenolate ion (L⁻) and , NCS⁻, (NC)₂N⁻, OAc⁻ as coligands, complexes having the formula [Ni(L)(N₃)] (1), [Ni(L)(NCS)]₂ (2), [Ni₂(L)₂(OAc)(N(CN)₂)]_n (3) were prepared and structurally characterized. In 1, Ni(II) has a square planar geometry and phenolate oxygen is involved in dipolar ?N^δ+ interaction with electrophilic central nitrogen atom of coordinated azide ion. Complex 2 is dimeric in nature and nickel(II) is penta-coordinated. Compounds 1 and 2 exist as centrosymmetric dimers made up of a pair of R and S enantiomers of L. In 3, an acetate and phenoxo bridged dinickel complex is present which is further linked to a zig-zag coordination polymer by the dicyanamide ion. In a given chain of 3, both L have same enantiomeric form and either RR or SS dimers are repeated along the chain. The magnetic properties are described.     

The inheritance of resistance to Verticillium wilt caused by race 1 isolates of <Emphasis Type="Italic">Verticillium dahliae</Emphasis> in the lettuce cultivar La Brillante

Verticillium wilt of lettuce caused by Verticillium dahliae can cause severe economic damage to lettuce producers. Complete resistance to race 1 isolates is available in Lactuca sativa cultivar (cv.) La Brillante and understanding the genetic basis of this resistance will aid development of new resistant cultivars. F₁ and F₂ families from crosses between La Brillante and three iceberg cultivars as well as a recombinant inbred line population derived from L. sativa cv. Salinas 88 × La Brillante were evaluated for disease incidence and disease severity in replicated greenhouse and field experiments. One hundred and six molecular markers were used to generate a genetic map from Salinas 88 × La Brillante and for detection of quantitative trait loci. Segregation was consistent with a single dominant gene of major effect which we are naming Verticillium resistance 1 (Vr1). The gene described large portions of the phenotypic variance (R ² = 0.49–0.68) and was mapped to linkage group 9 coincident with an expressed sequence tag marker (QGD8I16.yg.ab1) that has sequence similarity with the Ve gene that confers resistance to V. dahliae race 1 in tomato. The simple inheritance of resistance indicates that breeding procedures designed for single genes will be applicable for developing resistant cultivars. QGD8I16.yg.ab1 is a good candidate for functional analysis and development of markers suitable for marker-assisted selection.     

A comparison of vanadyl acetylacetonate complexes of N2O heteroscorpionate ligands that vary systematically in donor set

We have successfully prepared a series of vanadyl complexes with N₂O heteroscorpionate ligands and have characterized their cis and trans geometrical isomers both in solution and the solid state. The major difference between the isomers, and between the various oxygen atom donors of the N₂O scorpionate ligands, is in their redox potentials which can span almost a volt for this ostensively similar set of compounds. Such data may be useful in screening vanadium complexes for potential biological activity.     

Preperoxisomal vesicles can form in the absence of Pex3

We demonstrate that the peroxin Pex3 is not required for the formation of peroxisomal membrane structures in yeast pex3 mutant cells. Notably, pex3 mutant cells already contain reticular and vesicular structures that harbor key proteins of the peroxisomal receptor docking complex—Pex13 and Pex14—as well as the matrix proteins Pex8 and alcohol oxidase. Other peroxisomal membrane proteins in these cells are unstable and transiently localized to the cytosol (Pex10, Pmp47) or endoplasmic reticulum (Pex11). These reticular and vesicular structures are more abundant in cells of a pex3 atg1 double deletion strain, as the absence of Pex3 may render them susceptible to autophagic degradation, which is blocked in this double mutant. Contrary to earlier suggestions, peroxisomes are not formed de novo from the endoplasmic reticulum when the PEX3 gene is reintroduced in pex3 cells. Instead, we find that reintroduced Pex3 sorts to the preperoxisomal structures in pex3 cells, after which these structures mature into normal peroxisomes.     

Dynamic association of the PI3P-interacting Mon1-Ccz1 GEF with vacuoles is controlled through its phosphorylation by the type 1 casein kinase Yck3

Maturation of organelles in the endolysosomal pathway requires exchange of the early endosomal GTPase Rab5/Vps21 for the late endosomal Rab7/Ypt7. The Rab exchange depends on the guanine nucleotide exchange factor activity of the Mon1-Ccz1 heterodimer for Ypt7. Here we investigate vacuole binding and recycling of Mon1-Ccz1. We find that Mon1-Ccz1 is absent on vacuoles lacking the phosphatidic acid phosphatase Pah1, which also lack Ypt7, the phosphatidylinositol 3-kinase Vps34, and the lipid phosphatidylinositol 3-phosphate (PI3P). Interaction of Mon1-Ccz1 with wild-type vacuoles requires PI3P, as shown in competition experiments. We also find that Mon1 is released from vacuoles during the fusion reaction and its release requires its phosphorylation by the type 1 casein kinase Yck3. In contrast, Mon1 is retained on vacuoles lacking Yck3 or when Mon1 phosphorylation sites are mutated. Phosphorylation and release of Mon1 is restored with addition of recombinant Yck3. Together the results show that Mon1 is recruited to endosomes and vacuoles by PI3P and, likely after activating Ypt7, is phosphorylated and released from vacuoles for recycling.