Regulation of fruit and seed response to heat and drought by sugars as nutrients and signals

A large body of evidence shows that sugars function both as nutrients and signals to regulate fruit and seed set under normal and stress conditions including heat and drought. Inadequate sucrose import to, and its degradation within, reproductive organs cause fruit and seed abortion under heat and drought. As nutrients, sucrose-derived hexoses provide carbon skeletons and energy for growth and development of fruits and seeds. Sugar metabolism can also alleviate the impact of stress on fruit and seed through facilitating biosynthesis of heat shock proteins (Hsps) and non-enzymic antioxidants (e.g. glutathione, ascorbic acid), which collectively maintain the integrity of membranes and prevent programmed cell death (PCD) through protecting proteins and scavenging reactive oxygen species (ROS). In parallel, sugars (sucrose, glucose and fructose), also exert signalling roles through cross-talk with hormone and ROS signalling pathways and by mediating cell division and PCD. At the same time, emerging data indicate that sugar-derived signalling systems, including trehalose-6 phosphate (T6P), sucrose non-fermenting related kinase-1 (SnRK) and the target of rapamycin (TOR) kinase complex also play important roles in regulating plant development through modulating nutrient and energy signalling and metabolic processes, especially under abiotic stresses where sugar availability is low. This review aims to evaluate recent progress of research on abiotic stress responses of reproductive organs focusing on roles of sugar metabolism and signalling and addressing the possible biochemical and molecular mechanism by which sugars regulate fruit and seed set under heat and drought

Spontaneous large-scale autolysis in Clostridium acetobutylicum contributes to generation of more spores

Autolysis is a widespread phenomenon in bacteria. In batch fermentation of Clostridium acetobutylicum ATCC 824, there is a spontaneous large-scale autolysis phenomenon with significant decrease of cell density immediately after exponential phase. To unravel the role of autolysis, an autolysin-coding gene, CA_C0554, was disrupted by using ClosTron system to obtain the mutant C. acetobutylicum lyc::int(72). The lower final cell density and faster cell density decrease rate of C. acetobutylicum ATCC 824 than those of C. acetobutylicum lyc::int(72) indicates that CA_C0554 was an important but not the sole autolysin-coding gene responding for the large-scale autolysis. Similar glucose utilization and solvents production but obvious lower cell density of C. acetobutylicum ATCC 824 comparing to C. acetobutylicum lyc::int(72) suggests that lysed C. acetobutylicum ATCC 824 cells were metabolic inactive. On the contrary, the spore density of C. acetobutylicum ATCC 824 is 26.1% higher than that of C. acetobutylicum lyc::int(72) in the final culture broth of batch fermentation. We speculated that spontaneous autolysis of metabolic-inactive cells provided nutrients for the sporulating cells. The present study suggests that one important biological role of spontaneous large-scale autolysis in C. acetobutylicum ATCC 824 batch fermentation is contributing to generation of more spores during sporulation

A simple, rapid and reliable protocol to localize hydrogen peroxide in large plant organs by DAB-mediated tissue printing

Hydrogen peroxide (H2O2) is a major reactive oxygen species (ROS) and plays diverse roles in plant development and stress responses. However, its localization in large and thick plant organs (e.g. stem, roots and fruits), other than leaves, has proven to be challenging due to the difficulties for the commonly used H2O2-specific chemicals, such as 3, 3’-diaminobenzidine (DAB), cerium chloride (CeCl3) and 2’, 7’-dichlorofluorescin diacetate (H2DCF-DA), to penetrate those organs. Theoretically, the reaction of endogenous H2O2 with these chemicals could be facilitated by using thin organ sections. However, the rapid production of wound-induced H2O2 associated with this procedure inevitably disturbs the original distribution of H2O2 in vivo. Here, by employing tomato seedling stems and fruits as testing materials, we report a novel, simple and rapid protocol to localize H2O2 in those organs using DAB-mediated tissue printing. The rapidity of the protocol (within 15 s) completely avoided the interference of wound-induced H2O2 during experimentation. Moreover, the H2O2 signal on the printing was stable for at least 1 h with no or little background produced. We conclude that DAB-mediated tissue printing developed here provide a new feasible and reliable method to localize H2O2 in large plant organs, hence should have broad applications in studying ROS biology

Citrus PH5-like H+-ATPase genes: identification and transcript analysis to investigate their possible relationship with citrate accumulation in fruits

PH5 is a petunia gene that encodes a plasma membrane H+-ATPase and determines the vacuolar pH. The citrate content of fruit cell vacuoles influences citrus organoleptic qualities. Although citrus could have PH5-like homologs that are involved in citrate accumulation, the details are still unknown. In this study, extensive data-mining with the PH5 sequence and PCR amplification confirmed that there are at least eight PH5-like genes (CsPH1-8) in the citrus genome. CsPHs have a molecular mass of approximately 100 kDa, and they have high similarity to PhPH5, AtAHA10 or AtAHA2 (from 64.6% to 80.9%). They contain 13-21 exons and 12-20 introns and were evenly distributed into four subgroups of the P3A-subfamily (CsPH1, CsPH2, and CsPH3 in Group I, CsPH4 and CsPH5 in Group II, CsPH6 in Group IV, and CsPH7 and CsPH8 in Group III together with PhPH5). A transcript analysis showed that CsPH1, 3, and 4 were predominantly expressed in mature leaves, whereas CsPH2 and 7 were predominantly expressed in roots, CsPH5 and 6 were predominantly expressed in flowers, and CsPH8 was predominantly expressed in fruit juice sacs. Moreover, the CsPH transcript profiles differed between orange and pummelo, as well as between high-acid and low-acid cultivars. The low-acid orange ‘Honganliu’ exhibits low transcript levels of CsPH3, CsPH4, CsPH5, and CsPH8, whereas the acid-free pummelo has only a low transcript level of CsPH8. In addition, ABA injection increased the citrate content significantly, which was accompanied by the obvious induction of CsPH2, 6, 7, and 8 transcript levels. Taken together, we suggest that CsPH8 seems likely to regulate citrate accumulation in the citrus fruit vacuole

Temporal and spatial dynamics of archaeal communities in two freshwater lakes at different trophic status

In either eutrophic Dianchi Lake or mesotrophic Erhai Lake, the abundance, diversity and structure of archaeaplankton communities in spring were different from those in summer. In summer, archaeaplankton abundance generally decreased in Dianchi Lake but increased in Erhai Lake, while archaeaplankton diversity increased in both lakes. These two lakes had distinct archaeaplankton community structure. Archaeaplankton abundance was influenced by organic content, while trophic status determined archaeaplankton diversity and structure. Moreover, in summer, lake sediment archaeal abundance considerably decreased. Sediment archaeal abundance showed a remarkable spatial change in spring but only a slight one in summer. The evident spatial change of sediment archaeal diversity occurred in both seasons. In Dianchi Lake, sediment archaeal community structure in summer was remarkably different from that in spring. Compared to Erhai Lake, Dianchi Lake had relatively high sediment archaeal abundance but low diversity. These two lakes differed remarkably in sediment archaeal community structure. Trophic status determined sediment archaeal abundance, diversity and structure. Archaeal diversity in sediment was much higher than that in water. Water and sediment habitats differed greatly in archaeal community structure. Euryarchaeota predominated in water column, but showed much lower proportion in sediment. Bathyarchaeota was an important component of sediment archaeal community

Parcellation of the Primary Cerebral Cortices based on Local Connectivity Profiles

Primary cerebral cortices are of great importance for our understanding of the human brain. Although their functions are relatively monomodal, primary cerebral cortices have been suggested to compromise structurally and functionally distinct subregions from many evidences, for example, cytoarchitectionics, myeloarchitectonics and functional brain imaging. In recent years, structural connectivity-based parcellation using diffusion MRI has been extensively used to do parcellation of subcortical areas and association cortex. However, it has rarely been employed to primary cerebral cortices. In connectivity-based parcellation, connectivity profiles are very vital. Different researchers used different information of connectivity profiles, such as global connectivity profiles (the connectivity information from seed to the whole brain) and long connectivity profiles (the connectivity information from seed to other brain regions after excluding the seed). Given that primary cerebral cortices are rich of local hierarchical connections and possess high local functional connectivity profiles, we proposed that local connectivity profiles (the connectivity information in the seed region of interest (ROI)) might be used for parcellating primary cerebral cortices. Global, long and local connectivity profiles were compared on M1, A1, S1 and V1. We found that results using the three were all in good consistency with cytoarchitectonic results. More importantly, results using local connectivity profiles showed less inter-subject variability than results using the other two. This suggests that for parcellation of primary cerebral cortices local connectivity profiles are superior to global and long connectivity profiles. This also infers us that different connectivity profiles should be adopted according to the characteristics of the cerebral cortices

Oleanolic acid induces the type III secretion system of Ralstonia solanacearum

Ralstonia solanacearum, the causal agent of bacterial wilt, can naturally infect a wide range of host plants. The type III secretion system (T3SS) is a major virulence determinant in this bacterium. Studies have shown that plant derived compounds are able to inhibit or induce the T3SS in some plant pathogenic bacteria, though no specific T3SS inhibitor or inducer has yet been identified in R. solanacearum. In this study, a total of 50 different compounds were screened and almost half of them (22 of 50) significantly inhibited or induced the T3SS expression of R. solanacearum. Based on the strong induction activity on T3SS, the T3SS inducer oleanolic acid (OA) was chosen for further study. We found that OA induced the expression of T3SS through the HrpG-HrpB pathway. Some type III effector genes were induced in T3SS inducing medium supplemented with OA. In addition, OA targeted only the T3SS and did not affect other virulence determinants. Finally, we observed that induction of T3SS by OA accelerated disease progress on tobacco. Overall our results suggest that plant-derived compounds are an abundant source of R. solanacearum T3SS regulators, which could prove useful as tools to interrogate the regulation of this key virulence pathway

Distinct changes in functional connectivity in posteromedial cortex subregions during the progress of Alzheimer’s disease

Alzheimer’s disease is a progressive neurodegenerative disorder which causes dementia, especially in the elderly. The posteromedial cortex, which consists of several subregions involved in distinct functions, is one of the critical regions associated with the progression and severity of Alzheimer’s disease. However, previous studies always ignored the heterogeneity of the posteromedial cortex and focused on one stage of Alzheimer’s disease. Using resting-state functional magnetic resonance imaging, we studied the respective alterations of each subregion within the posteromedial cortex along the progression of Alzheimer’s disease. Our data set consisted of 21 healthy controls, 18 patients with mild cognitive impairment, 17 patients with mild Alzheimer’s disease, and 18 patients with severe Alzheimer’s disease. We investigated the functional alterations of each subregion within the posteromedial cortex in different stages of Alzheimer’s disease. We found that subregions within the posteromedial cortex have differential vulnerability in Alzheimer’s disease. Disruptions in functional connectivity began in the transition area between the precuneus and the posterior cingulate cortex and then extended to other subregions of the posteromedial cortex. In addition, each of these subregions was associated with distinct alterations in the functional networks that we were able to relate to Alzheimer’s disease. Our research demonstrated functional changes within the posteromedial cortex in the progression of Alzheimer’s disease and may elucidate potential biomarkers for clinical applications

Multiple horizontal transfers of bacteriophage WO and host Wolbachia in fig wasps in a closed community

Wolbachia-bacteriophage WO is a good model system for studying interactions between bacteria and viruses. Previous surveys of insect hosts have been conducted via sampling from open or semi-open communities; however, no studies have reported the infection patterns of phage WO of insects living in a closed community. Figs and fig wasps form a peculiar closed community in which the Ficus tree provides a compact syconium habitat for a variety of fig wasps. Therefore, in this study, we performed a thorough survey of Wolbachia and bacteriophage WO infection patterns in a total of 1406 individuals from 23 fig wasps species living on three different fig tree species. The infection rates of Wolbachia and phage WO were 82.6% (19/23) and 39.1% (9/23), respectively. Additionally, phage WO from fig wasps showed strong insect host specificity based on orf7 sequences from fig wasps and 21 other insect species. Probably due to the physical barrier of fig syconium, most phage WO from fig wasps form a special clade. Phylogenetic analysis showed the absence of congruence between WO and host Wolbachia, WO and insect host, as well as Wolbachia and fig wasps, suggesting that both Wolbachia and phage WO exchanged frequently and independently within the closed syconium. Thus, the infection pattern of bacteriophage WO from fig wasps appeared quite different from that in other insects living outside, although the effect and the transfer routes of phage WO are unclear, which need to be investigated in the future

The trait anger affects conflict inhibition: a Go/Nogo ERP study

To explore the time course of inhibitory control in high trait anger individuals, we recorded and analyzed ERP data relevant to visual Go/Nogo task in high and low trait anger participants. Compared with low trait anger participants, high trait anger participants revealed faster RTs in the Go/Nogo task. The nogo effect of N2 related to conflict monitoring was similar between two groups. While the P3go was larger in high than low trait anger groups, the P3nogo did not differ between two groups. This induced the smaller nogo effect of P3 in high than that in low trait anger group, which is closely related to the actual inhibition of the motor system. These data suggest the reduced later stage of inhibitory processes in high trait anger individuals, implicating the dysfunction of inhibitory control