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Summary Several plant proteins are preferentially localized to one end of a cell, allowing a polarity to be assigned to the cell. These cell polarity proteins often exhibit coordinated patterns between neighboring cells, termed tissue cell polarity. Tissue cell polarity is widespread in plants and can influence how cells grow, divide, and differentiate [1, 2, 3, 4, 5]. However, it is unclear whether cell polarity is established through cell-intrinsic or -extrinsic mechanisms and how polarity is coupled to growth. To address these issues, we analyzed the behavior of a tissue cell polarity protein BASL (BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE) in the simplifying context of cultured cell filaments and in protoplasts before and during regeneration. We show that BASL is polarly localized when ectopically expressed in tobacco BY-2 cell cultures. Ectopic BASL is found preferentially at the developing tips of cell filaments, likely marking a polarized molecular address. Polarity can shift during the cell cycle and is resistant to treatment with microtubule, actin or auxin transport inhibitors. BASL also exhibits polar localization in spherical protoplasts, in contrast to other polarity proteins so far tested. BASL polarity within protoplasts is dynamic and resistant to auxin transport inhibitors. As protoplasts regenerate, polarity remains dynamic in isotropically growing cells but becomes fixed in anisotropic cells and aligns with the axis of cell growth. Our findings suggest that plant cells have an intrinsic ability to polarize and that environmental or developmental cues may act by biasing the direction of this polarity and thus the orientation of anisotropic growth., Graphical Abstract, Highlights • Ectopic GFP-BASL reveals a polarized molecular address in tobacco suspension cells • Spherical protoplasts have an intrinsic ability to polarize • Polarity is aligned with growth in regenerating protoplasts growing anisotropically • Polarity is dynamic in regenerating protoplasts growing isotropically, Chan et al. reveal a polarized molecular address in tobacco suspension cells through ectopic expression of GFP-BASL. They show protoplasts have an intrinsic ability to polarize and that polarity is aligned with the growth axis as they regenerate. Tissue-wide cues may bias the direction of polarity and thus orient anisotropic growth.

Cardiomyocyte β3-adrenoceptors (β3-ARs) coupled to soluble guanylyl cyclase (sGC)-dependent production of the second messenger 3’,5’-cyclic guanosine monophosphate (cGMP) have been shown to protect from heart failure. However, the exact localization of these receptors to fine membrane structures and subcellular compartmentation of β3-AR/cGMP signals underpinning this protection in health and disease remain elusive. Here, we used a Förster Resonance Energy Transfer (FRET)-based cGMP biosensor combined with scanning ion conductance microscopy (SICM) to show that functional β3-ARs are mostly confined to the T-tubules of healthy rat cardiomyocytes. Heart failure, induced via myocardial infarction, causes a decrease of the cGMP levels generated by these receptors and a change of subcellular cGMP compartmentation. Furthermore, attenuated cGMP signals led to impaired phosphodiesterase two dependent negative cGMP-to-cAMP cross-talk. In conclusion, topographic and functional reorganization of the β3-AR/cGMP signalosome happens in heart failure and should be considered when designing new therapies acting via this receptor.

Early stages of a beneficial relationship Plants benefit from widespread symbiosis with arbuscular mycorrhizal fungi. This symbiosis between plant and fungus aids plants in capturing mineral and micronutrients from the soil. Gutjahr et al. have now identified a component of an intracellular receptor, the hydrolase DWARF 14 LIKE, required in rice roots for initiating the symbiosis. A similar receptor detects karrikins in smoke that signal opportunity for fireweed to grow after a forest fire. Science , this issue p. 1521

Summary Tissue-wide polarity fields, in which cell polarity is coordinated across the tissue, have been described for planar organs such as the Drosophila wing and are considered important for coordinating growth and differentiation [1]. In planar plant organs, such as leaves, polarity fields have been identified for subgroups of cells, such as stomatal lineages [2], trichomes [3, 4], serrations [5], or early developmental stages [6]. Here, we show that ectopic induction of the stomatal protein BASL (BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE) reveals a tissue-wide epidermal polarity field in leaves throughout development. Ectopic GFP-BASL is typically localized toward the proximal end of cells and to one lobe of mature pavement cells, revealing a polarity field that aligns with the proximodistal axis of the leaf (base to tip). The polarity field is largely parallel to the midline of the leaf but diverges in more lateral positions, particularly at later stages in development, suggesting it may be deformed during growth. The polarity field is observed in the speechless mutant, showing that it is independent of stomatal lineages, and is observed in isotropic cells, showing that cell shape anisotropy is not required for orienting polarity. Ectopic BASL forms convergence and divergence points at serrations, mirroring epidermal PIN polarity patterns, suggesting a common underlying polarity mechanism. Thus, we show that similar to the situation in animals, planar plant organs have a tissue-wide cell polarity field, and this may provide a general cellular mechanism for guiding growth and differentiation., Graphical Abstract, Highlights • Ectopic expression of BASL in Arabidopsis leaves reveals coordinated polarity • The ectopic BASL polarity field is independent of the stomatal lineage • The polarity field reorients around serrations, mirroring PIN1 polarity, Mansfield et al. demonstrate a coordinated tissue cell polarity field in the Arabidopsis leaf epidermis revealed by ectopic expression of BASL. This polarity field is independent of the stomatal lineage and reorients around serrations, mirroring the polarity of PIN1.

Background— Mutations in sarcomeric and cytoskeletal proteins are a major cause of hereditary cardiomyopathies, but our knowledge remains incomplete as to how the genetic defects execute their effects. Methods and Results— We used cysteine and glycine-rich protein 3, a known cardiomyopathy gene, in a yeast 2-hybrid screen and identified zinc-finger and BTB domain-containing protein 17 ( ZBTB17 ) as a novel interacting partner. ZBTB17 is a transcription factor that contains the peak association signal (rs10927875) at the replicated 1p36 cardiomyopathy locus. ZBTB17 expression protected cardiac myocytes from apoptosis in vitro and in a mouse model with cardiac myocyte–specific deletion of Zbtb17 , which develops cardiomyopathy and fibrosis after biomechanical stress. ZBTB17 also regulated cardiac myocyte hypertrophy in vitro and in vivo in a calcineurin-dependent manner. Conclusions— We revealed new functions for ZBTB17 in the heart, a transcription factor that may play a role as a novel cardiomyopathy gene.

Helicoverpa spp. is the primary pest in the Australian fresh-market tomato industry. We describe the spatial distribution of Helicoverpa spp. eggs on fresh-market tomato crops in the Goulburn Valley region of Victoria, and present a sequential sampling plan for monitoring population densities. The distribution of Helicoverpa spp. eggs was highly contagious, as indicated by a Taylor's b-value of 1.59. This high level of contagion meant that relatively large sample sizes would need to be collected to obtain an estimate of population density. High-precision sampling plans generally necessitated impractical sample sizes, and thus the plan we present is a relatively low-precision level plan (SE/mean = 0.3). Nonetheless, this level of precision is considered adequate for most agronomic scenarios. The plan was validated using a statistical re-sampling approach. The level of precision achieved was generally close to the nominal level. Likewise, the number of samples collected generally showed little departure from the theoretically calculated minimum sample size.

During two growing seasons, the use of an attract-and-kill system for control of Carpophilus spp. (Coleoptera: Nitidulidae) and the effective range or drawing power of the attract-and-kill stations were examined in stone fruit orchards in the Goulburn Valley, northern Victoria, Australia. Three attract-and-kill stations, baited with synthetic aggregation pheromone plus co-attractant, were placed about 50 m apart in the upwind corner of each treated block 5 ‐ 6 weeks before the fruit began to ripen. Large numbers of Carpophilus spp. were caught in the attract-and-kill stations immediately after placement. By the time fruit had ripened, the number of Carpophilus spp. caught had decreased greatly. Fruit damage caused by Carpophilus spp. in treated blocks, especially in 2000 ‐2001 season, was almost zero (0.1% and 0.6%) in trees and on the ground, respectively, whereas the damage levels in control blocks were 5.2% and 19.9% in trees and on the ground, respectively. This study indicates that excellent protection of ripening stone fruit may be achieved by using attract-and kill-stations.

Background: Phosphate is released by the cardiac actomyosin ATPase during contraction. Results: Stretching active cardiac muscle decreases phosphate release within milliseconds. Conclusion: Mechanical stimuli such as stretch cause an immediate change in actomyosin ATPase kinetics. Significance: Stretch facilitates a powerful contraction by increasing cross-bridges in a pre-power stroke state, and changes cytoplasmic phosphate flux, which may influence energetic homeostasis. The contractile performance of the heart is linked to the energy that is available to it. Yet, the heart needs to respond quickly to changing demands. During diastole, the heart fills with blood and the heart chambers expand. Upon activation, contraction of cardiac muscle expels blood into the circulation. Early in systole, parts of the left ventricle are being stretched by incoming blood, before contraction causes shrinking of the ventricle. We explore here the effect of stretch of contracting permeabilized cardiac trabeculae of the rat on the rate of inorganic phosphate (Pi) release resulting from ATP hydrolysis, using a fluorescent sensor for Pi with millisecond time resolution. Stretch immediately reduces the rate of Pi release, an effect observed both at full calcium activation (32 μmol/liter of Ca2+), and at a physiological activation level of 1 μmol/liter of Ca2+. The results suggest that stretch redistributes the actomyosin cross-bridges toward their Pi-containing state. The redistribution means that a greater fraction of cross-bridges will be poised to rapidly produce a force-generating transition and movement, compared with cross-bridges that have not been subjected to stretch. At the same time stretch modifies the Pi balance in the cytoplasm, which may act as a cytoplasmic signal for energy turnover.

We have investigated a transgenic mouse model of inherited dilated cardiomyopathy that stably expresses the ACTC E361G mutation at around 50% of total actin in the heart. F-actin isolated from ACTC E361G mouse hearts was incorporated into thin filaments with native human tropomyosin and troponin and compared with NTG mouse actin by in vitro motility assay. There was no significant difference in sliding speed, fraction of filaments motile or Ca(2+)-sensitivity (ratio EC(50) E361G/NTG=0.95+/-0.08). The Ca(2+)-sensitivity of force in skinned trabeculae from ACTC E361G mice was slightly higher than NTG (EC(50) E361G/NTG=0.78+/-0.04). The molecular phenotype was revealed when troponin was dephosphorylated; Ca(2+)-sensitivity of E361G-containing thin filaments was now lower than NTG (EC(50) E361G(dPTn)/NTG(dPTn)=2.15+/-0.09). We demonstrated that this was due to uncoupling of Ca(2+)-sensitivity from troponin I phosphorylation by comparing Ca(2+)-sensitivity of phosphorylated and dephosphorylated thin filaments. For NTG actin-containing thin filaments EC(50) native/dPTn=3.0+/-0.3 but for E361G-containing thin filaments EC(50) native/dPTn=1.04+/-0.07.We studied contractility in isolated myocytes and found no significant differences under basal conditions. We measured cardiac performance by cine-MRI, echocardiography and with a conductance catheter over a period of 4 to 18 months and found minimal systematic differences between NTG and ACTC E361G mice under basal conditions. However, the increase in septal thickening, ejection fraction, heart rate and cardiac output following dobutamine treatment was significantly less in ACTC E361G mice compared with NTG. We propose that the ACTC E361G mutation uncouples myofilament Ca(2+)-sensitivity from Troponin I phosphorylation and blunts the response to adrenergic stimulation, leading to a reduced cardiac reserve with consequent contractile dysfunction under stress, leading to dilated cardiomyopathy.

Purpose: Mutations in several sarcomeric Z-disc proteins, such as muscle LIM protein (MLP), have been shown to cause hypertrophic and dilated cardiomyopathies. The transcription factor MIP1 has been identified as a novel MLP interacting protein which is important in the cardiac stress response and able to cause cardiac hypertrophy in vivo. Here we examine, in vitro, the mechanisms behind this cardiac phenotype and investigate potential disease causing mutations in this protein. Methods and Results: Adenoviral overexpression of MIP1 in adult and neonatal rat cardiomyocytes (NRCMs) showed that MIP1 induces cardiac myocyte hypertrophy, as seen by increased cell size and real-time impedance measurements (n=10, p

Purposes: Mutations in sarcomeric proteins are a major cause of hereditary cardiomyopathies. Muscle LIM protein (MLP, CSRP3) is involved in cardiac mechanosensation and important for myocyte-specific survival pathways. Identification of novel MLP interacting proteins (MIP) may provide novel insights into underlying molecular mechanisms of human disease. Methods and Results: Yeast two-hybrid screens identified MIP1 as a novel MLP interacting protein, which is a member of the poxvirus and zinc-finger (POZ or BTB) domain/zinc-finger transcription factor family. The interaction was confirmed by co-immunoprecipitation, cross-linking of recombinant proteins and immunohistochemistry. Cardiac myocyte specific conditional knockout mice (cKO) were generated and underwent transverse aortic constriction (TAC) to unveil potential gene effects. After 4 weeks of TAC left ventricles of cKO mice became dilated (LVIDd mm: 3.74 vs 3.44, LVIDs mm: 2.00 vs 1.65, cKO: n=10, Control: n=8, P

Mechanosensation and mechanotransduction are fundamental aspects of biology, but the link between physical stimuli and biological responses remains not well understood. The perception of mechanical stimuli, their conversion into biochemical signals, and the transmission of these signals are particularly important for dynamic organs such as the heart. Various concepts have been introduced to explain mechanosensation at the molecular level, including effects on signalosomes, tensegrity, or direct activation (or inactivation) of enzymes. Striated muscles, including cardiac myocytes, differ from other cells in that they contain sarcomeres which are essential for the generation of forces and which play additional roles in mechanosensation. The majority of cardiomyopathy causing candidate genes encode structural proteins among which titin probably is the most important one. Due to its elastic elements, titin is a length sensor and also plays a role as a tension sensor (i.e., stress sensation). The recent discovery of titin mutations being a major cause of dilated cardiomyopathy (DCM) also underpins the importance of mechanosensation and mechanotransduction in the pathogenesis of heart failure. Here, we focus on sarcomere-related mechanisms, discuss recent findings, and provide a link to cardiomyopathy and associated heart failure.