Spatiotemporal profiles of gene activity in stamen delineate nucleo-cytoplasmic interaction in a male-sterile somatic cybrid citrus.

Cytoplasmic male sterility (CMS) has long been used to produce seedless fruits in perennial woody crops like citrus. A male-sterile somatic cybrid citrus (G1 + HBP) was generated by protoplast fusion between a CMS callus parent 'Guoqing No. 1' Satsuma mandarin (Citrus unshiu, G1) and a fertile mesophyll parent Hirado Buntan pummelo (Citrus grandis, HBP). To uncover the male-sterile mechanism of G1 + HBP, we compared the transcriptome profiles of stamen organ and cell types at five stages between G1 + HBP and HBP, including the initial stamen primordia, enlarged stamen primordia, pollen mother cells, tetrads, and microspores captured by laser microdissection. The stamen organ and cell types showed distinct gene expression profiles. A majority of genes involved in stamen development were differentially expressed, especially CgAP3.2, which was downregulated in enlarged stamen primordia and upregulated in tetrads of G1 + HBP compared with HBP. Jasmonic acid- and auxin-related biological processes were enriched among the differentially expressed genes of stamen primordia, and the content of jasmonic acid biosynthesis metabolites was higher in flower buds and anthers of G1 + HBP. In contrast, the content of auxin biosynthesis metabolites was lower in G1 + HBP. The mitochondrial tricarboxylic acid cycle and oxidative phosphorylation processes were enriched among the differentially expressed genes in stamen primordia, meiocytes, and microspores, indicating the dysfunction of mitochondria in stamen organ and cell types of G1 + HBP. Taken together, the results indicate that malfunction of mitochondria-nuclear interaction might cause disorder in stamen development, and thus lead to male sterility in the citrus cybrid.

The miR399-CsUBC24 Module Regulates Reproductive Development and Male Fertility in Citrus.

MicroRNA399 (miR399) regulates phosphate homeostasis in plants by down-regulating the expression of PHOSPHATE2 (PHO2, or UBC24 encoding the ubiquitin-conjugating E2 enzyme). We previously identified CsmiR399a.1 in a small RNA sequencing screen of a male-sterile somatic cytoplasmic hybrid (or cybrid) of pummelo (Citrus grandis). Here, we report that miR399 affects reproductive development and male fertility in citrus. Down-regulation of CsmiR399a.1 using a short tandem target mimic (STTM) led to abnormal floral development, inhibition of anther dehiscence, and decreased pollen fertility. When grown in inorganic phosphate (Pi)-sufficient conditions, CsmiR399a.1-STTM plants had lower total phosphorus content in their leaves than the wild type and showed typical symptoms of Pi deficiency. In CsmiR399a.1-STTM plants, the expression of genes involved in starch metabolism and Pi homeostasis was significantly different than in the wild type. Thus, we conclude that miR399-STTM mimicked Pi deficiency, disturbed starch metabolism, and was responsible for pollen grain collapse in the transgenic lines. We identified CsUBC24, a citrus homolog of Arabidopsis (Arabidopsis thaliana) AtUBC24 (PHO2), as a target of CsmiR399a.1 that physically interacts with the floral development regulators SEPALLATA family (CsSEP1.1, CsSEP1.2, and CsSEP3) and the anther dehiscence regulator INDUCER OF CBF EXPRESSION1 (CsICE1). We hypothesize that CsUBC24 downregulates the CsSEPs, which disrupts the floral meristem identity regulatory network and leads to developmental abnormalities in flowers. By interacting with CsICE1, CsUBC24 disturbs stomate function on the anther surface, which inhibits anther dehiscence. These findings indicate that a miR399-based mechanism influences both reproductive development and male fertility in citrus.

A method to predict both the relaxation time of quantum tunneling of magnetization and the effective barrier of magnetic reversal for a Kramers single-ion magnet.

In this work, a theoretical method for the prediction of both the relaxation time of quantum tunneling of magnetization (τQTM) and the effective barrier of magnetic reversal (Ueff) is proposed for single-ion magnet (SIM) systems of Kramers type. The reliability of theoretical τQTM is tested within a large series of 18 lanthanide SIMs. Compared to the experimental results, the deviations of theoretical τQTM are within one order of magnitude for 11 tested SIMs and the largest order-of-magnitude deviation is only 1.86. In the aspect of Ueff, for 5 typical high-performance Dy-SIMs of the local coordination mode of a pentagonal bipyramid, the relative deviations of theoretical values lie within the range of 1.4-7.2%. Thus this method possesses good reliability, at least in the aspect of the order of magnitude. Besides an empirical estimate of the local magnetic field experienced by the central ion, for a given SIM, one ab initio calculation, providing accurate g-factors of both ground and excited Kramers doublets (KDs), is the only computational cost. Therefore this method has a high degree of both reliability and efficiency. Based on the temperature dependence of theoretically predicted Ueff and its contributions from various KDs, some mechanistic information on the magnetic relaxation could be given by this method too. Therefore it is reasonable to expect the bright prospect of this method in the aspects of both the interpretation of the existing experimental results and rational design of future high-performance SIMs.

Study of multi-objective path planning method for vehicles.

To address the problems associated with single-objective path planning, herein, we propose a multi-objective path planning method that takes into account emissions, fuel consumption, and time as travel demands. First, a fuel consumption and emission estimation model, suitable for coupling with a dynamic transportation network, is established, and then, the multi-objective path planning model is presented. In addition, the analytic hierarchy process (AHP) and gray relational analysis are used to derive relative priorities of each sub-objective according to driver preference. The above two models are combined with an improved Dijkstra algorithm to perform multi-objective path planning based on dynamic time-dependent road conditions. Finally, the method is verified using real-world vehicle experiments on actual roads. Compared to single-objective path planning, the multi-objective planning method meets travel needs and can save time and fuel, thereby providing greater environmental protection while still considering driver preferences.

Constructing organic superacids from superhalogens is a rational route as verified by DFT calculations.

The construction route of organic superacids from the combination of organic superhalogens and protons is verified to be a rational one based on a systematic theoretical study covering different planar conjugated backbones, e.g., [C5H5]- and [BC5H6]-, and electron-withdrawing substituents, e.g., -F, -CN and -NO2. In both the gas phase and the solution phase, the acidities of the composites here have a consistent strengthening with the increase of the vertical electron detachment energy of the superhalogen part. Decomposition of the acidity into different contributions further verifies the dominant role of the superhalogen part in the variation of the acidity. Thus, tuning of the acidity of systems of this type could be achieved via rational design of the constituent part of the superhalogen. That is to say, the design of a novel organic superacid with enhanced properties could be guided by the search for a new strong superhalogen of organic nature eventually. Having provided important contributions to the topic of superhalogens, theoretical calculation should be trusted to provide useful guidance for the research of organic superacids and could be expected to promote related experimental studies in the near future.

Why do higher VDEs of superhalogen not ensure improved stabilities of the noble gas hydrides promoted by them? A high-level ab initio case study.

A series of 20 composite structures, consisting of superhalogen and noble gas (Ng) hydrides, was explored via high-level coupled-cluster single, double and perturbative triple excitations calculations in this work. The existence of these composites, as local minima on the potential energy surface, arises from the charge transfer from the Ng hydride part to the superhalogen moiety. Clearly, this transfer could lead to stabilizing the interaction of the ionic type between the two components. The driving force of the charge transfer should be the high vertical electron detachment energy (VDE) of the superhalogen part leading to its enough capability of extracting the electron from the Ng hydride moiety. However, except triggering the ionic attractive interaction, there is nomonotonic correlation between the VDE value and the thermodynamic stability of the whole composite. This counter-intuitive result actually originates from the fact that, irrespective of various superhalogens, only two of their F ligands interact with the Ng atoms directly. Thus, although leading to higher VDE values, the increase in the number of electronegative ligands of the superhalogen moiety does not affect the stabilizing interaction of the composites here directly. In other words, with the necessary charge transfer generated, further increase of the VDE does not ensure the improvement of the thermodynamic stabilities of the whole composite. Moreover, in the transition state of the exothermic dissociation channel, more F atoms will give rise to higher probability of additional attractions between the F and H atoms which should lower the energy barrier. That is to say, increasing VDE, i.e., having more F atoms in many cases, will probably reduce the kinetic stability. Knowing the inevitable existence of the exothermic channel, kinetic stability is crucial to the ultimate goal of experimental observation of these Ng hydrides. Thus, in some cases, only the superhalogen itself may not provide enough information for the correct prediction on the properties of the whole composites. The understanding of the superhalogen-based composites will provide valuable information on the functional properties as well as the application potential of superhalogen clusters. Thus, the corresponding researches should focus on not only the superhalogen itself but also other related aspects, especially the details of the interaction between different parts.