Variation in the promoter of the sorbitol dehydrogenase gene MdSDH2 affects binding of the transcription factor MdABI3 and alters fructose content in apple fruit.

Fructose (Fru) content is a key determinant of fruit sweetness and quality. An F1 hybrid population of the apple cultivars 'Honeycrisp' × 'Qinguan' was used to investigate the quantitative trait locus (QTL) regions and genes controlling Fru content in fruit. A stable QTL on linkage group (LG) 01 in 'Honeycrisp' was detected on the single nucleotide polymorphism (SNP) genetic linkage maps. In this region, a sorbitol dehydrogenase (SDH) gene, MdSDH2, was detected and showed promoter variations and differential expression patterns between 'Honeycrisp' and 'Qinguan' fruits as well as their hybrids. A SNP variant (A/G) in the MdSDH2 promoter region (SDH2p-491) affected the binding ability of the transcription factor MdABI3, which can affect the expression of MdSDH2. Promoter sequences with an A nucleotide at SDH2p-491 had stronger binding affinity for MdABI3 than those with a G. Among 27 domesticated apple cultivars and wild relatives, this SNP (A/G) was associated with Fru content. Our results indicate that MdSDH2 can alter Fru content as the major regulatory gene and that ABA signaling might be involved in Fru content accumulation in apple fruit.

F-box protein MdAMR1L1 regulates ascorbate biosynthesis in apple by modulating GDP-mannose pyrophosphorylase.

Ascorbate (Asc) is an important antioxidant in plants and humans that plays key roles in various physiological processes. Understanding the regulation of Asc content in fruit plants is important for improving plant resiliency and optimizing Asc in food. Here, we found that both the transcript level and protein abundance of Asc Mannose pathway Regulator 1 Like 1 (MdAMR1L1) was negatively associated with Asc levels during the development of apple (Malus × domestica) fruit. The overexpression or silencing of MdAMR1L1 in apple indicated that MdAMR1L1 negatively regulated Asc levels. However, in the leaves of MdAMR1L1-overexpressing apple lines, the transcript levels of the Asc synthesis gene Guanosine diphosphate-mannose pyrophosphorylase MdGMP1 were increased, while its protein levels and enzyme activity were reduced. This occurred because the MdAMR1L1 protein interacted with MdGMP1 and promoted its degradation via the ubiquitination pathway to inhibit Asc synthesis at the post-translational level. MdERF98, an apple ethylene response factor, whose transcription was modulated by Asc level, is directly bound to the promoter of MdGMP1 to promote the transcription of MdGMP1. These findings provide insights into the regulatory mechanism of Asc biosynthesis in apples and revealed potential opportunities to improve fruit Asc levels.

Probabilistic Hierarchical Quantum Information Splitting of Arbitrary Multi-Qubit States.

By utilizing the non-maximally entangled four-qubit cluster states as the quantum channel, we first propose a hierarchical quantum information splitting scheme of arbitrary three-qubit states among three agents with a certain probability. Then we generalize the scheme to arbitrary multi-qubit states. Hierarchy is reflected on the different abilities of agents to restore the target state. The high-grade agent only needs the help of one low-grade agent, while the low-grade agent requires all the other agents' assistance. The designated receiver performs positive operator-valued measurement (POVM) which is elaborately constructed with the aid of Hadamard matrix. It is worth mentioning that a general expression of recovery operation is derived to disclose the relationship with measurement outcomes. Moreover, the scheme is extended to multiple agents by means of the symmetry of cluster states.

Nitrogen Levels Regulate Sugar Metabolism and Transport in the Shoot Tips of Crabapple Plants.

To comprehensively understand the responses of carbohydrate metabolism and transport to different levels of nitrogen supply in growing shoot tips of crabapple (Malus hupehensis Rehd), enzyme activities and related genes involved in the sugar metabolism pathway were investigated. The nitrogen and chlorophyll content of plants increased with increasing nitrogen supply. High nitrogen application increased the net photosynthesis rate and the growth rate of shoot tips but decreased the synthesis capability of sucrose and sorbitol in mature leaves. However, the shoot tips of plants under high-nitrogen treatment had higher contents of sucrose and sorbitol than did those under low-nitrogen treatment, while the activity of sucrose phosphate synthase and aldose-6-phosphate was increased and the transporters MdSOT and MdSUT were up-regulated. Moreover, the activities of enzymes involved in sucrose and hexose metabolism (including sucrose synthase, fructokinase, and hexokinase) were enhanced in the shoot tips of plants under high-nitrogen conditions, and the expression levels of MdSUSY3 and MdHK1 were significantly up-regulated. These findings indicate that a high nitrogen supply increases the metabolic capacity of assimilatory substances in shoot tips, accelerates the efficiency of sugar utilization and eventually leads to a rapid increase in the growth of shoot tips. Our results highlight that high nitrogen increases the capacity of sugar unloading and metabolic utilization in growing shoot tissues.

Hybrid Toffoli gate on photons and quantum spins.

Quantum computation offers potential advantages in solving a number of interesting and difficult problems. Several controlled logic gates, the elemental building blocks of quantum computer, have been realized with various physical systems. A general technique was recently proposed that significantly reduces the realization complexity of multiple-control logic gates by harnessing multi-level information carriers. We present implementations of a key quantum circuit: the three-qubit Toffoli gate. By exploring the optical selection rules of one-sided optical microcavities, a Toffoli gate may be realized on all combinations of photon and quantum spins in the QD-cavity. The three general controlled-NOT gates are involved using an auxiliary photon with two degrees of freedom. Our results show that photons and quantum spins may be used alternatively in quantum information processing.

Photonic ququart logic assisted by the cavity-QED system.

Universal quantum logic gates are important elements for a quantum computer. In contrast to previous constructions of qubit systems, we investigate the possibility of ququart systems (four-dimensional states) dependent on two DOFs of photon systems. We propose some useful one-parameter four-dimensional quantum transformations for the construction of universal ququart logic gates. The interface between the spin of a photon and an electron spin confined in a quantum dot embedded in a microcavity is applied to build universal ququart logic gates on the photon system with two freedoms. Our elementary controlled-ququart gates cost no more than 8 CNOT gates in a qubit system, which is far less than the 104 CNOT gates required for a general four-qubit logic gate. The ququart logic is also used to generate useful hyperentanglements and hyperentanglement-assisted quantum error-correcting code, which may be available in modern physical technology.

Controlled Photon Switch Assisted by Coupled Quantum Dots.

Quantum switch is a primitive element in quantum network communication. In contrast to previous switch schemes on one degree of freedom (DOF) of quantum systems, we consider controlled switches of photon system with two DOFs. These controlled photon switches are constructed by exploring the optical selection rules derived from the quantum-dot spins in one-sided optical microcavities. Several double controlled-NOT gate on different joint systems are greatly simplified with an auxiliary DOF of the controlling photon. The photon switches show that two DOFs of photons can be independently transmitted in quantum networks. This result reduces the quantum resources for quantum network communication.