Potato late blight field resistance from QTL dPI09c is conferred by the NB-LRR gene R8.

Following the often short-lived protection that major nucleotide binding, leucine-rich-repeat (NB-LRR) resistance genes offer against the potato pathogen Phytophthora infestans, field resistance was thought to provide a more durable alternative to prevent late blight disease. We previously identified the QTL dPI09c on potato chromosome 9 as a more durable field resistance source against late blight. Here, the resistance QTL was fine-mapped to a 186 kb region. The interval corresponds to a larger, 389 kb, genomic region in the potato reference genome of Solanum tuberosum Group Phureja doubled monoploid clone DM1-3 (DM) and from which functional NB-LRRs R8, R9a, Rpi-moc1, and Rpi_vnt1 have arisen independently in wild species. dRenSeq analysis of parental clones alongside resistant and susceptible bulks of the segregating population B3C1HP showed full sequence representation of R8. This was independently validated using long-range PCR and screening of a bespoke bacterial artificial chromosome library. The latter enabled a comparative analysis of the sequence variation in this locus in diverse Solanaceae. We reveal for the first time that broad spectrum and durable field resistance against P. infestans is conferred by the NB-LRR gene R8, which is thought to provide narrow spectrum race-specific resistance.

Molecular Marker-Assisted Selection for Frost Tolerance in a Diallel Population of Potato.

A multi-parental population is an innovative tool for mapping large numbers of loci and genetic modifications, particularly where they have been used for breeding and pre-breeding in crops. Frost injury is an environmental stress factor that greatly affects the growth, development, production efficiency, and geographical distribution of crops. No reported study has focused on genetic mapping and molecular marker development using diallel populations of potatoes. In this study, 23 successful cross combinations, obtained by a half diallel cross among 16 parents, including eight frost-tolerant advanced breeding lines and eight cultivars, were used to map the genetic loci for frost tolerance and to create a molecular marker-assisted selection (MAS) system. Three candidate regions related to frost tolerance on chromosomes II, V, and IX were mapped by bulked segregant analysis (BSA). Furthermore, six SNP markers associated with frost tolerance from candidate regions were developed and validated. Above all, a MAS system for the frost tolerance screening of early breeding offspring was established. This study highlights the practical advantages of applying diallel populations to broaden and improve frost-tolerant germplasm resources.

Conditional QTL underlying resistance to late blight in a diploid potato population.

A large number of quantitative trait loci (QTL) for resistance to late blight of potato have been reported with a "conventional" method in which each phenotypic trait reflects the cumulative genetic effects for the duration of the disease process. However, as genes controlling response to disease may have unique contributions with specific temporal features, it is important to consider the phenotype as dynamic. Here, using the net genetic effects evidenced at consecutive time points during disease development, we report the first conditional mapping of QTL underlying late blight resistance in potato under five environments in Peru. Six conditional QTL were mapped, one each on chromosome 2, 7 and 12 and three on chromosome 9. These QTL represent distinct contributions to the phenotypic variation at different stages of disease development. By comparison, when conventional mapping was conducted, only one QTL was detected on chromosome 9. This QTL was the same as one of the conditional QTL. The results imply that conditional QTL reflect genes that function at particular stages during the host-pathogen interaction. The dynamics revealed by conditional QTL mapping could contribute to the understanding of the molecular mechanism of late blight resistance and these QTL could be used to target genes for marker development or manipulation to improve resistance.

QTL analysis of tuber shape in a diploid potato population.

Tuber shape is one of the most important traits for potato breeding. Since poor or irregular shape increases the difficulty of handling and processing, researching the inheritance of potato tuber shape for potato breeding is highly important. To efficiently identify QTL for tuber shape, a diploid potato population (PM7) was generated by self-pollinated M6 (S. chacoense). A QTL TScha6 for tuber shape was identified by the QTL-seq approach at 50.91-59.93 Mb on chromosome 6 in the potato DM reference genome. To confirm TScha6, four SSR and twenty CAPS markers around the QTL were developed and the TScha6 was narrowed down to an interval of ~ 1.85 Mb. The CAPS marker C6-58.27_665 linked to TScha6 was then used to screen 86 potato cultivars and advanced breeding lines. The tuber length/width (LW) ratio was significantly correlated with the presence/absence of C6-58.27_665, and the correlation coefficient was r = 0.55 (p < 0.01). These results showed that C6-58.27_665 could be applied in marker-assisted selection (MAS) for tuber shape breeding in the future. Our research sets the important stage for the future cloning of the tuber shape gene and utilities of the marker in the breeding program.

The GABA(A) receptor mediates the hypnotic activity of melatonin in rats.

The present investigation assessed whether hypnotic activity of melatonin was mediated by the GABA(A) receptor in rats. Electroencephalography (EEG) was measured in this experiment. Melatonin, at a dose of 10 mg/kg ip, showed a significant sleep-promoting effect in rats. Flumazenil (3.5 and 7 mg/kg), a specific antagonist of the benzodiazepine (BZP) recognition site on the GABA(A) receptor, and picrotoxin (2 and 4 mg/kg), the ligand of the picrotoxin site on the GABA(A) receptor, seemed to be devoid of intrinsic influence on each sleep parameter when used alone, but they significantly antagonized the melatonin-induced increase in total sleep time (TS), slow-wave sleep time (SWS) and paradoxical sleep time (PS), and the decrease in time to sleep onset (TSO) and wakefulness time (W). A significant interaction was shown between melatonin and flumazenil or picrotoxin. When bicuculline methiodide (2 and 4 mg/kg), a specific antagonist of the GABA binding site on the GABA(A) receptor, was used together with melatonin, the melatonin-induced increase in TS, SWS and PS, and the decrease in W were abolished. However, there was no interaction between melatonin and bicuculline methiodide on sleep parameters except PS. These results indicate that the hypnotic activity of melatonin may be linked to the GABA(A) receptor and mediated through the BZP recognition site, the picrotoxin site on the GABA(A) receptor and partially through the GABA binding site on the GABA(A) receptor.

[Effect of atropine on the inhibition of melatonin to the unit discharges evoked in the posterior group of thalamic nuclei in cats].

AIM: To study the effect of atropine, muscarinic cholinergic antagonist, on the central analgesic action of melatonin (MT) and to explore the mechanism of MT analgesia. METHODS: As an indicator of visceral pain, the unit discharges of the neurons in the posterior group of thalamic nuclei (PO) were caused by stimulating the great splanchnic nerve (GSN) of the cat. The cranial stereotaxic and extracellular glass microelectrode record technique were used. The drugs were given through the intra-cranial-ventricle (icv). RESULTS: 0.1% MT (10 micrograms.kg-1, icv) was shown to inhibit the unit discharge of the neurons in PO of the cat, whether the long latency or the short latency, which was evoked by stimulating GSN. The inhibition of 0.1% MT (10 micrograms.kg-1, icv) on the short latency discharge of neurons in PO was antagonized by 0.1% atropine (20 micrograms, icv). However, 0.1% atropine (20 micrograms, icv) did not show antagonistic effect on the inhibition of 0.1% morphine (5 micrograms, icv) at the same latency. CONCLUSION: MT exhibited central analgesic action with mechanism different from morphine. It was suggested that the cholinergic system may be involved in analgesic process of MT.

[Advances in studies of biological clock gene].

The circadian clock genes, which generate and control the running of the circadian rhythms, exist in organisms ranging from prokaryotes to mammals. The oscillator genes and its coding proteins compose the feedback loops of circadian system. The kind, number and regulating route of clock genes are characterized by living things at different evolution levels. The molecular mechanism of the run of circadian clock genes in cyanobacteria, neurospore, fruit fly, mouse and human being is introduced in this article.

Ultrasound-induced release of GDNF from lipid coated microbubbles injected into striatum reduces hypoxic-ischemic injury in neonatal rats.

Previous studies showed that inflammation and apoptosis were involved in the pathogenesis of hypoxic-ischemic brain injury. The immature brain is particularly vulnerable to damage. Intracerebral injection of glial cell line-derived neurotrophic factor (GDNF) has been shown to reduce the injury induced by hypoxia-ischemia (HI). In this study, the neuroprotective effect of intracerebral ultrasound-induced dissolution of lipid-coated GDNF microbubbles was investigated in a neonatal rat model of hypoxic-ischemic brain injury. Hypoxic-ischemic injury was induced in 7-day-old rats in the present study. The rats with hypoxia-ischemia received intracerebral injections of GDNF-containing microbubbles (0.5 mg/kg). They then received low frequency ultrasound stimulation (20 kHz, 2 h intervals for a total of 24 h and each time lasted for 1 min) to induce release of GDNF into the right striatum. We found that low frequency ultrasound stimulation can induce lipid-coated GDNF microbubbles to release GDNF. Ultrasound-induced dissolution of lipid-coated GDNF microbubbles treatment reduced infarction volume and improved neurological outcomes in neonatal rats. In the meanwhile, the microbubbles attenuated the production of inducible nitric oxide synthase, nitric oxide and tumor necrosis factor-alpha, as well as the activation of caspase-3 in insulted side of brain in neonatal rats. These data demonstrated that ultrasound-induced dissolution of lipid-coated GDNF microbubbles treatment can provide a neuroprotective effect against hypoxia-ischemia in neonatal rats.

[The role of melatonin receptor and GABAA receptor in the sleeping time prolonged by melatonin in mice].

AIM: To observe the role of melatonin receptor and GABAA receptor in sleeping time prolonged by melatonin in mice. METHODS: The absence of the righting reflex was considered as the sleep onset and the duration of the loss of the righting reflex was recorded as the sleeping time. The effects of receptor agonist and antagonist on hypnotic activity of melatonin were studied in the paper. RESULTS: Prazosin hydrochloride, the blocker of melatonin 3 receptor, didn't affect the sleeping time prolonged by melatonin in mice. GABA, the endogenous agonist of GABA receptor, significantly potentiated the hypnotic activity of melatonin. When picrotoxin, the ligand of picrotoxin site on GABAA receptor, used together with melatonin, it significantly antagonized the sleeping time prolonged by melatonin, however, bicuculline, the specific antagonist of GABA binding site in GABAA receptor, didn't affect the hypnotic activity of melatonin in mice. CONCLUSION: Melatonin does not exhibit its potentiation sleeping time in mice through melatonin 3 receptor. Hypnotic activity of melatonin may be mediated through picrotoxin site on GABAA receptor.

Hypnotic activity of melatonin: involvement of semicarbazide hydrochloride, blocker of synthetic enzyme for GABA.

AIM: To assess the effect of semicarbazide hydrochloride (SCZ), the blocker of synthetic enzyme for GABA, on the hypnotic activity of melatonin. METHODS: Righting reflex method in mice and electroencephalography (EEG) in rats were used to determine effects of SCZ on sleep and hypnotic activity of melatonin. RESULTS: Melatonin displayed a marked hypnotic activity both in righting reflex experiment and EEG recording. SCZ had no influence on sleep parameters in mice and rats when it was used alone. However, it blocked the sleep-potentiation effect of melatonin in mice. SCZ also inhibited melatonin-induced increase in total sleep time, slow wave sleep time, and paradoxical sleep time, and prevented melatonin-induced decrease in awake time in rats. CONCLUSION: SCZ antagonized the hypnotic activity of melatonin. It is thought that the hypnotic activity of melatonin is mediated by GABAergic system.