The model suggests that in colder areas, the observed late-season buildup of the fly results from low winter survival and the movement of adults from areas with phenologically earlier populations.Berry curvature is a key to understand novel physical phenomena such as anomalous Hall effect, chiral anomaly, topological Hall effect, and spin-valley Hall effect. Moreover, the BC classifies the topology of a solid via a topological number that predicts the presence of protected states at its boundary. The response of a system governed by the BC is constrained by the Onsager relation in the linear order. This stringent constraint, however, is no longer valid in the high-order responses that are proportional to the second-order or even higher orders of the driving field. The integration over higher-order fields gives a nonlinear response of the system, contributing to the optical and transport responses . This finding not only provides a methodology to explore the momentum texture of the BC of a system, but also paves a way to utilize the response even though the linear order is vanishingly weak or when a large driving field makes the higher-order response exceed the linear order. To make use of the higher-order response has great potential for applications in rectification devices , photosensitive devices , and photovoltaic devices that potentially overcome the quantum efficiency limit.Recent studies on the higher-order response have invited nonmagnetic materials with broken centrosymmetry as a new member of the Hall effect family, so-called nonlinear Hall effect , characterized by a quadratic behavior of the Hall voltage with second harmonic frequencies in the presence of a perpendicular AC driving current. In the absence of the linear Hall effect due to time reversal symmetry, 25 liter plant pot the lowest-order Hall current is driven by the Berry curvature dipole.
Since the response is proportional to the gradient of the BC, tilted anticrossing bands and Weyl points are predicted to exhibit strong BCD that can generate a nonlinear Hall angle close to 90 degrees. As a result, the momentum-dependent texture of the BC based on the electronic structures is essential to understand the NLHE in which the evolution of BC momentum texture by lattice strain, interlayer twisting, and external electric fields can lead to NLHE-based device applications. Nevertheless, while the majority of studies on the NLHE have predominantly focused on exploring its transport properties, applications, and theoretical simulations, the direct experimental confirmation and comprehensive understanding of the BCD based on electronic structures have not yet been fully attained. This achievement would provide crucial insights into the underlying mechanism and controllability of the BCD. In this paper, we report the room temperature NLHE in NbIrTe4 thin flakes, which exhibit a frequency-doubled Hall conductivity proportional to the square of the driving current. We also demonstrate that the sign change in the NLHE at 150 K is induced by the sign change of the BCD because of the chemical potential shift at high temperatures. It is unambiguously evidenced by direct observation of a chemical potential shift in the temperature-dependent band dispersion using angle-resolved photo emission spectroscopy and calculated BCDs. Investigation of the electronic structures using ARPES and density functional theory also indicates that the main contributor of BCDs is a partial occupation of spin–orbit split bands. Our findings provide important insights into the momentum texture of the Berry curvature and into controlling the Berry curvature dipole hosting the NLHE, which can be utilized for NLHE-based devices.
It is often asserted and then assumed that fundamental research from model systems, such as Arabidopsis, is valuable because this knowledge would be utilized later to elucidate practical aspects of plant function in species of agronomic importance. This has been successful in like organs and developmental processes. For example, a regulatory module involved in photoperiod control of flowering has been elucidated through extensive research in Arabidopsis , and more recently this same mechanism has been shown to control flower time in Populus trichocarpa . Unexpectedly, Bohlenius et al. revealed that the same regulatory module is involved in the control of bud dormancy. This illustrates that components of regulatory mechanisms can be conserved across disparate developmental processes that share commonalities; a dependence on daylength and action in the shoot apex in the case of flowering and bud dormancy. Less is known about the utility of extending knowledge to a class of organ not even present in a given model species. The onset of ripening marks a transition in fruit development leading to changes in physiology involving sugar metabolism, softening, and color development. Most understanding of this process arises from work with climacteric fruits in which the control of ripening is predominately by ethylene. However, there are many fruits of economic importance that are nonclimacteric, such as grape, strawberry, and citrus, where the processes controlling the onset of ripening are still poorly understood. Study has traditionally focused on ethylene in climacteric fruits and on other hormones such as sugar and abscisic acid in non-climacteric fruits. However, there are numerous studies implicating ethylene in the ripening of non-climacteric fruits , and conversely, sugar and ABA in the ripening of climacteric fruits . In addition, other hormones have been show to influence the ripening processes such as auxin and brassinosteroids .
Fruit ripening in general involves the integration of multiple hormone signals. Climacteric and non-climacteric fruits are not delimited by phylogeny and both exist even among closely related species . This suggests that ripening in all fleshy fruit may have a common foundation. Sugar and ABA function as signals in many aspects of plant development and there are numerous lines of evidence correlating increases in sugar and ABA with the onset of ripening in grape . In field-grown berries, exogenous ABA increases anthocyanin accumulation , and in our own work berries fail to synthesize anthocyanins when sugar import into the berry is disrupted via phloem girdling prior to the onset of ripening . Finally, water deficits also result in increases in anthocyanin accumulation , and have been shown to increase ABA accumulation at the onset of ripening . Many studies investigating the role of sugar and ABA in ripening have focused on color development. In viticulture, the onset of ripening is traditionally referred to as veraison and is defined by the initiation of color development. More contemporary genomic studies demonstrate that color can act as a proxy for developmental stage in that individual grape berries of like color have similar global gene expression patterns . A previous study in our laboratory found that water deficits advanced the onset of color development, but sugar and anthocyanin accumulation remained closely linked . Furthermore, the induction of core flavonoid and anthocyanin-specific genes reflected this advancement as well . Therefore, in the current study, water deficit is used as a means to manipulate the timing of the onset of ripening in the field. There are few examples of studies focused on identifying the molecular mechanisms responsible for sugar and ABA action in grape, although several recent studies have demonstrated roles for sugar and ABA in controlling sugar metabolism. ABA stimulates acid invertase activity , and expression of the grape hexose transporter VvHT1 is regulated by both ABA and hexose . Two other recent studies have focused on core sugar and ABA-signaling components. A calcium-dependent protein kinase is regulated by ABA during ripening , and a study in grape cell culture provides evidence that sugar induced increases in anthocyanin accumulation are dependent on calcium, calmodulin, and kinase activity . In this study, we begin to examine the hypothesis that orthologous sugar and ABA-signaling components, black plastic plant pots characterized across such diverse processes as seed dormancy and stomatal control, function similarly in the control of the onset of ripening in fleshy fruit. This study employs a comprehensive approach in identifying novel sugar and ABA-signaling candidates in grape.
Ten gene families, containing sugar and ABA-signaling components elucidated in model systems, were considered including; the putative sucrose sensor SUT2, core G-protein signaling components GPA1 and RGS1, hexokinases , PP2C protein phosphatases, Snf1-related kinases , and the sugar-related WRKY, and ABA-related homeodomain–leucine zipper, or homeobox , ABRE-binding factor , and AP2 transcription factors . Their orthologous families in grape were identified, and the expression of individual genes were characterized in control- and deficit-irrigated, field-grown Cabernet Sauvignon. The onset of ripening was induced in cultured immature berries with sugar and ABA treatments. Finally, the effect of exogenous sugar and ABA on the expression of several key orthologs was investigated in berry culture.The field experiment was the same as presented in Castellarin et al. . In short, experiments were conducted during 2006 in a commercial vineyard of R.H. Phillips Winery using Vitis vinifera ‘‘Cabernet Sauvignon’’ clone 337 grafted onto rootstock 140R. Two irrigation treatments were established. Irrigation was applied to control vines in order to maintain midday leaf water potential between -0.9 and -1.2 MPa. Irrigation was cut off to early deficit vines at fruit set until 77 days after anthesis ; then vines were irrigated at the C rate till 133 DAA. Plant water status was monitored weekly by measuring midday leaf water potential according to Matthews et al. . Each treatment was replicated four times in 0.5-ha plots dispersed over a 36-ha vineyard according to a randomized complete block design. Samples were collected randomly from ten vines located in the central row of the plots. Berries were sampled six times between 27 June and 5 October , when the grapes were harvested. Twenty berries were collected from each plot for use in studies of gene expression. During the onset of ripening, samples of green and red berries were collected separately from the same clusters and analyzed separately.Cabernet Sauvignon clusters were collected from fieldgrown vines at 61 DAA. Clusters were surfaced sterilized for 10 s in a 70% ethanol solution, 10 min in a 1% bleach solution, and then rinsed three times with sterilized water. Berries were removed from the clusters by cutting the stem at the peduncle level, and the peduncle was removed from the rest of the fruit with a scalpel. Berries were weighed and individually cultured for 23 days in 20 mL glass vials filled with 7 mL of six different 1% agarose media 2% sucrose, 10% sucrose, 200 lM ABA alone, 2% sucrose 200 lM ABA, 10% sucrose 10 lM ABA, 10% sucrose 200 lM ABA. The 2 and 10% sucrose concentrations used in this study approximate sugar concentrations of berries prior to and at , the onset of ripening in the field . Each treatment was replicated ten times. Berry color changes were visually analyzed twice, 10 days after T0 and at the end of the experiment. Elasticity was measured at T0 and at the end of the experiment. In short, berry elasticity was determined non-destructively using a custom-fabricated instrument, which measured force and displacement during berry compression. As described in Thomas et al. , the observed force/displacement relation was fit using SAS PROC NLIN to that expected for compression of a perfectly elastic sphere . 23 days after T0, berries were collected from the vials, weighed, and stored at -80 C till the tissues were processed for the RNA extractions. Three berries from the 2% sucrose, 10% sucrose, 10% sucrose 10 lM ABA, 10% sucrose 200 lM ABA treatments were peeled and total RNA was extracted from each individual skin following the procedure described above.Utilizing the sequenced grape genome , 67 genes were identified representing orthologs of sugar and ABA-related genes in 10 gene families . The genomic complexity of these families varied from small families with just one or few genes to large families made up of nearly 100 genes . Small gene families were comprehensively characterized for all grape orthologs, while only those subgroups containing genes specifically shown to be involved in sugar and ABA signaling were included for large gene families. Given the scope of this work, we focused primarily on those gene families encoding the following well characterized orthologs the Arabidopsis Class I HB transcription factors, the Arabidopsis ABA-insensitive mutants, abi1 and abi2, encoding PP2C protein phosphatases, and the WRKY transcription factors SUSIBA2, AtWRKY4, and AtWRKY34. Other gene families are summarized and referenced as supplemental material when pertinent. The homeodomain–leucine zipper, or homeobox transcription factors represent a medium-sized gene family with approximately 47 members in Arabidopsis.