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Abstract Cereal/legume intercropping is becoming a popular production strategy for higher crop yields and net profits with reduced inputs and environmental impact. However, the effects of different spatial arrangements on the growth, grain yield, nitrogen uptake, and land-use advantage of wheat/soybean relay intercropping are still unclear, particularly under arid irrigated conditions. Therefore, in a three-year field study from 2018 to 2021, soybean was relay intercropped with wheat in different crop configurations (0.9 m, narrow strips; 1.8 m, medium strips; and 2.7 m, wide strips), and the results of intercropping systems were compared with their sole systems. Results revealed that intercrops with wide strips outperformed the narrow and medium strips, when the objective was to obtain higher total leaf area, dry matter, nitrogen uptake, and grain yield on a given land area due to reduced interspecific competition between intercrops. Specifically, at maturity, wide strips increased the dry matter accumulation (37% and 58%) and its distribution in roots (37% and 55%), straw (40% and 61%), and grains (30% and 46%) of wheat and soybean, respectively, compared to narrow strips. This enhanced dry matter in wide strips improved the soybean’s competitive ability (by 17%) but reduced the wheat’s competitive ability (by 12%) compared with narrow strips. Noticeably, all intercropping systems accumulated a significantly higher amount of nitrogen than sole systems, revealing that wheat/soybean relay intercropping requires fewer anthropogenic inputs (nitrogen) and exerts less pressure on the ecosystem than sole systems. Overall, in wide strips, intercropped wheat and soybean achieved 62% and 71% of sole wheat and soybean yield, respectively, which increased the greater total system yield (by 19%), total land equivalent ratio (by 24%), and net profit (by 34%) of wide strips compared to narrow strips. Our study, therefore, implies that the growth parameters, grain yields, nutrient accumulation, and land-use advantage of intercrop species could be improved with the proper spatial arrangement in cereal/legume intercropping systems.

To keep up with technology changes and industry trends, it is essential for Information Systems (IS) programs to maintain up to date curricula. In doing so, IS educators need to determine what the IS core is and implement it in their curriculum. This study performed a descriptive analysis of 2,229 core courses offered by 394 undergraduate IS programs in the United States. The result presents a panoramic snapshot of the IS core in the nation from the perspective of IS core curricula. By mapping those core courses to the most recent IS model curriculum, IS 2010, this study also reports how many IS programs offer each of the seven core courses in IS 2010. Moreover, these core courses were examined from three different perspectives: school type, accreditation, and research orientation.

Recognition of sweet, bitter and umami tastes requires the nonvesicular release from taste bud cells of ATP, which acts as a neurotransmitter to activate afferent neural gustatory pathways (1). However, how ATP is released to fulfil this function is not fully understood. Here we show that calcium homeostasis modulator 1 (CALHM1), a voltage-gated ion channel (2,3), is indispensable for taste-stimuli-evoked ATP release from sweet-, bitter- and umami-sensing taste bud cells. Calhm1 knockout mice have severely impaired perceptions of sweet, bitter and umami compounds, whereas their recognition of sour and salty tastes remains mostly normal. Calhm1 deficiency affects taste perception without interfering with taste cell development or integrity. CALHM1 is expressed specifically in sweet/bitter/umami-sensing type II taste bud cells. Its heterologous expression induces a novel ATP permeability that releases ATP from cells in response to manipulations that activate the CALHM1 ion channel. Knockout of Calhm1 strongly reduces voltage-gated currents in type II cells and taste-evoked ATP release from taste buds without affecting the excitability of taste cells by taste stimuli. Thus, CALHM1 is a voltage-gated ATP-release channel required for sweet, bitter and umami taste perception., Tastes are sensed by dedicated receptor cells in taste buds, which are composed of three anatomically distinct types of cells: types I, II and III. Only type III cells, which [...]

Copper is an essential trace element that may serve as a signaling molecule in the nervous system. Here we show that extracellular [Cu.sup.2+] is a potent inhibitor of BK and Shaker [K.sup.+] channels. At low micromolar concentrations, [Cu.sup.2+] rapidly and reversibly reduces macrosocopic [K.sup.+] conductance ([G.sub.K]) evoked from mSlo1 BK channels by membrane depolarization. [G.sub.K] is reduced in a dose-dependent manner with an [IC.sub.50] and Hill coefficient of ~2 [micro]M and 1.0, respectively. Saturating 100 [micro]M [Cu.sup.2+] shifts the [G.sub.K]-V relation by +74 mV and reduces [G.sub.Kmax] by 27% without affecting single channel conductance. However, 100 [micro]M [Cu.sup.2+] fails to inhibit [G.sub.K] when applied during membrane depolarization, suggesting that [Cu.sup.2+] interacts poorly with the activated channel. Of other transition metal ions tested, only [Zn.sup.2-] and [Cd.sup.2+] had significant effects at 100 DM with [IC.sub.50]s > 0.5 mM, suggesting the binding site is [Cu.sup.2+] selective. Mutation of external Cys or His residues did not alter [Cu.sup.2+] sensitivity. However, four putative [Cu.sup.2+]-coordinating residues were identified (D133, Q151, D153, and R207) in transmembrane segments S1, $2, and $4 of the mSlo1 voltage sensor, based on the ability of substitutions at these positions to alter [Cu.sup.2+] and/or [Cd.sup.2+] sensitivity. Consistent with the presence of acidic residues in the binding site, [Cu.sup.2+] sensitivity was reduced at low extracellular pH. The three charged positions in S1, $2, and $4 are highly conserved among voltage-gated channels and could play a general role in metal sensitivity. We demonstrate that Shaker, like mSlo1, is much more sensitive to [Cu.sup.2+] than [Zn.sup.2+] and that sensitivity to these metals is altered by mutating the conserved positions in S1 or $4 or reducing pH. Our results suggest that the voltage sensor forms a state- and pH-dependent, metal-selective binding pocket that may be occupied by [Cu.sup.2+] at physiologically relevant concentrations to inhibit activation of BK and other channels.

BK (Slol) potassium channels arc activated by millimolar intracellular [Mg.sup.2+] as well as micromolar [Ca.sup.2+] and membrane depolarization. [Mg.sup.2+] and [Ca.sup.2+] act ill all approximately additive manner m different binding sites to shift t conductance-voltage ([G.sub.K]-V) relation, suggesting that these ligands might work through functionally similar but independent mechanisms. However, we lind that the mechanism of [Mg.sup.2+] action is highly dependent on voltage sensor activation and therefore differs fundamentally from that of [Ca.sup.2+]. Evidence that [Ca.sup.2+] acts independently of voltage sensor activation includes an ability to increase open probability ([P.sub.o]) at extreme negative voltages where voltage sensors are in the resting state; 2 [micro]M [Ca.sup.2+] increases [P.sub.o] more than 15-fold at -120 mV. However 10 mM [Mg.sup.2+] which has an effect on the [G.sub.K]-V relation similar to 2 [micro]M [Ca.sup.2+], has no detectable effect on [P.sub.o] when voltage sensors are in the resting state. Gating currents are only slightly altered by [Mg.sup.2+] when channels are closed, indicating that [Mg.sup.2+] does not act merely to promote voltage sensor activation. Indeed, channel opening is facilitated in a voltage-independent manner by [Mg.sup.2+] in a mutam (R210C) whose voltage sensors are constitutively activated. Thus, 10 mM [Mg.sup.2+] increases [P.sub.o] only when voltage sensors are activated, effectively strengthening the allosteric coupling of voltage sensor activation to channel opening. Increasing [Mg.sup.2+] from 10 to 100 mM, to occupy very low affinity binding sites, has additional effects on gating that more closely resemble those of [Ca.sup.2+]. The effects of [Mg.sup.2+] on steady-state activation and [I.sub.K] kinetics are discussed in terms of an allosteric gating scheme and the state-dependent interactions between [Mg.sup.2+] and voltage sensor that may underlie this mechanism.

The activation of large conductance [Ca.sup.2+]-activated (BK) potassium channels is weakly voltage dependent compared to Shaker and other voltage-gated [K.sup.+] ([K.sub.v]) channels. Yet BK and Kv channels share many conserved charged residues in transmembrane segments S1-S4. We mutated these residues individually in mS1o1 BK channels to determine their role in voltage gating, and characterized the voltage dependence of steady-state activation ([P.sub.o]) and [I.sub.K] kinetics ([tau] ([I.sub.K])) over an extended voltage range in 0-50 [micro]M [[Ca.sub.2+].sub.i]. mS1o1 contains several positively charged arginines in S4, but only one (R213) together with residues in S2 (D153, R167) and S3 (D186) are potentially voltage sensing based on the ability of charge-altering mutations to reduce the maximal voltage dependence of [P.sup.o]. The voltage dependence of [P.sub.o] and [tau]([I.sub.K]) at extreme negative potentials was also reduced, implying that the closed-open conformational change and voltage sensor activation share a common source of gating charge. Although the position of charged residues in the BK and [K.sub.v] channel sequence appears conserved, the distribution of voltage-sensing residues is not. Thus the weak voltage dependence of BK channel activation does not merely reflect a lack of charge but likely differences with respect to [K.sub.v] channels in the position and movement of charged residues within the electric field. Although mutation of most sites in S1-S4 did not reduce gating charge, they often altered the equilibrium constant for voltage sensor activation. In particular, neutralization of R207 or R210 in S4 stabilizes the activated state by 3-7 kcal mol- 1, indicating a strong contribution of non-voltage-sensing residues to channel function, consistent with their participation in state-dependent salt bridge interactions. Mutations in S4 and S3 (R210E, D186A, and E180A) also unexpectedly weakened the allosteric coupling of voltage sensor activation to channel opening. The implications of our findings for BK channel voltage gating and general mechanisms of voltage sensor activation are discussed.

The S4 transmembrane segment is the primary voltage sensor in voltage-dependent ion channels. Its movement in response to changes in membrane potential leads to the opening of the activation gate, which is formed by a separate structural component, the S6 segment. Here we show in voltage-, C[a.sup.2+-], and M[g.sup.2+]-dependent, large conductance [K.sup.+] channels that the S4 segment participates not only in voltage- but also M[g.sup.2+]-dependent activation. Mutations in S4 and the S4-S5 linker alter voltage-dependent activation and have little or no effect on activation by micromolar C[a.sup.2+]. However, a subset of these mutations in the C-terminal half of S4 and in the S4-S5 linker either reduce or abolish the M[g.sup.2+] sensitivity of channel gating. Cysteine residues substituted into positions R210 and R213, marking the boundary between S4 mutations that alter M[g.sup.2+] sensitivity and those that do not, are accessible to a modifying reagent [sodium (2-sulfonatoethyl)methane-thiosulfonate] (MTSES) from the extracellular and intracellular side of the membrane, respectively, at -80 mV. This implies that interactions between Sa, and a cytoplasmic domain may be involved in M[g.sup.2+]-dependent activation. These results indicate that the voltage sensor is critical for M[g.sup.2+]-dependent activation and the coupling between the voltage sensor and channel gate is a converging point for voltage- and M[g.sup.2+]-dependent activation pathways.

Temperature strongly influences the intensity of taste, but it remains understudied despite its physiological, hedonic, and commercial implications. The relative roles of the peripheral gustatory and somatosensory systems innervating the oral cavity in mediating thermal effects on taste sensation and perception are poorly understood. Type II taste-bud cells, responsible for sensing sweet, bitter umami, and appetitive NaCl, release neurotransmitters to gustatory neurons by the generation of action potentials, but the effects of temperature on action potentials and the underlying voltage-gated conductances are unknown. Here, we used patch-clamp electrophysiology to explore the effects of temperature on acutely isolated type II taste-bud cell electrical excitability and whole cell conductances. Our data reveal that temperature strongly affects action potential generation, properties, and frequency and suggest that thermal sensitivities of underlying voltage-gated Na + and K + channel conductances provide a mechanism for how and whether voltage-gated Na + and K + channels in the peripheral gustatory system contribute to the influence of temperature on taste sensitivity and perception. NEW & NOTEWORTHY The temperature of food affects how it tastes. Nevertheless, the mechanisms involved are not well understood, particularly whether the physiology of taste-bud cells in the mouth is involved. Here we show that the electrical activity of type II taste-bud cells that sense sweet, bitter, and umami substances is strongly influenced by temperature. These results suggest a mechanism for the influence of temperature on the intensity of taste perception that resides in taste buds themselves.

Calcium homeostasis modulator protein-1 (CALHM1) and its Caenorhabditis elegans (ce) homolog, CLHM-1, belong to a new family of physiologically important ion channels that are regulated by voltage and extracellular Ca 2+ (Ca 2+ o ) but lack a canonical voltage-sensing domain. Consequently, the intrinsic voltage-dependent gating mechanisms for CALHM channels are unknown. Here, we performed voltage-clamp experiments on ceCLHM-1 chimeric, deletion, insertion, and point mutants to assess the role of the NH 2 terminus (NT) in CALHM channel gating. Analyses of chimeric channels in which the ceCLHM-1 and human (h)CALHM1 NH 2 termini were interchanged showed that the hCALHM1 NT destabilized channel-closed states, whereas the ceCLHM-1 NT had a stabilizing effect. In the absence of Ca 2+ o , deletion of up to eight amino acids from the ceCLHM-1 NT caused a hyperpolarizing shift in the conductance-voltage relationship with little effect on voltage-dependent slope. However, deletion of nine or more amino acids decreased voltage dependence and induced a residual conductance at hyperpolarized voltages. Insertion of amino acids into the NH 2 -terminal helix also decreased voltage dependence but did not prevent channel closure. Mutation of ceCLHM-1 valine 9 and glutamine 13 altered half-maximal activation and voltage dependence, respectively, in 0 Ca 2+ In 2 mM Ca 2+ o , ceCLHM-1 NH 2 -terminal deletion and point mutant channels closed completely at hyperpolarized voltages with apparent affinity for Ca 2+ o indistinguishable from wild-type ceCLHM-1, although the ceCLHM-1 valine 9 mutant exhibited an altered conductance-voltage relationship and kinetics. We conclude that the NT plays critical roles modulating voltage dependence and stabilizing the closed states of CALHM channels., (Copyright © 2017 the American Physiological Society.)

Disruption of neuronal Ca(2+) homeostasis contributes to neurodegenerative diseases through mechanisms that are not fully understood. A polymorphism in CALHM1, a recently described ion channel that regulates intracellular Ca(2+) levels, is a possible risk factor for late-onset Alzheimer's disease. Since there are six potentially redundant CALHM family members in humans, the physiological and pathophysiological consequences of CALHM1 function in vivo remain unclear. The nematode Caenorhabditis elegans expresses a single CALHM1 homolog, CLHM-1. Here we find that CLHM-1 is expressed at the plasma membrane of sensory neurons and muscles. Like human CALHM1, C. elegans CLHM-1 is a Ca(2+)-permeable ion channel regulated by voltage and extracellular Ca(2+). Loss of clhm-1 in the body-wall muscles disrupts locomotory kinematics and biomechanics, demonstrating that CLHM-1 has a physiologically significant role in vivo. The motility defects observed in clhm-1 mutant animals can be rescued by muscle-specific expression of either C. elegans CLHM-1 or human CALHM1, suggesting that the function of these proteins is conserved in vivo. Overexpression of either C. elegans CLHM-1 or human CALHM1 in neurons is toxic, causing degeneration through a necrotic-like mechanism that is partially Ca(2+) dependent. Our data show that CLHM-1 is a functionally conserved ion channel that plays an important but potentially toxic role in excitable cell function.

Much data, including crystallographic, support structural models of sodium and potassium channels consisting of S1-S4 transmembrane segments (the "voltage-sensing domain") clustered around a central pore-forming region (S5-S6 segments and the intervening loop). Voltage gated sodium channels have four non-identical domains which differentiates them from the homotetrameric potassium channels that form the basis for current structural models. Since potassium and sodium channels also exhibit many different functional characteristics and the fourth domain (D4) of sodium channels differs in function from other domains (D1-D3), we have explored its structure in order to determine whether segments in D4 of sodium channels differ significantly from that determined for potassium channels. We have probed the secondary and tertiary structure and the role of the individual amino acid residues of the S2D4) of Na(v)1.4 by employing cysteine-scanning mutagenesis (with tryptophan and glutamine substituted for native cysteine). A Fourier transform power spectrum of perturbations in free energy of steady-state inactivation gating (using midpoint potentials and slopes of Boltzmann equation fits of channel availability, h(infinity)-V plots) indicates a substantial amount of alpha-helical structure in S2D4 (peak at 106 degrees, alpha-Periodicity Index (alpha-PI) of 3.10), This conclusion is supported by alpha-PI values of 3.28 and 2.84 for the perturbations in rate constants of entry into (beta) and exit from (alpha) fast inactivation at 0 mV for mutant channels relative to WT channels assuming a simple two-state model for transition from the open to inactivated state. The results of cysteine substitution at the two most sensitive sites of the S2D4 alpha-helix (N1382 and E1392C) support the existence of electrostatic network interactions between S2 and other transmembrane segments within Na(v)1.4D4 similar to but not identical to those proposed for K+ channels.