Molecular Mechanisms Underlying Abscisic Acid/Gibberellin Balance in the Control of Seed Dormancy and Germination in Cereals

Seed dormancy is an adaptive trait that does not allow the germination of an intact viable seed under favorable environmental conditions. Non-dormant seeds or seeds with low level of dormancy can germinate readily under optimal environmental conditions, and such a trait leads to preharvest sprouting, germination of seeds on the mother plant prior to harvest, which significantly reduces the yield and quality of cereal crops. High level of dormancy, on the other hand, may lead to non-uniform germination and seedling establishment. Therefore, intermediate dormancy is considered to be a desirable trait as it prevents the problems of sprouting and allows uniformity of postharvest germination of seeds. Induction, maintenance, and release of seed dormancy are complex physiological processes that are influenced by a wide range of endogenous and environmental factors. Plant hormones, mainly abscisic acid (ABA) and gibberellin (GA), are the major endogenous factors that act antagonistically in the control of seed dormancy and germination; ABA positively regulates the induction and maintenance of dormancy, while GA enhances germination. Significant progress has been made in recent years in the elucidation of molecular mechanisms regulating ABA/GA balance and thereby dormancy and germination in cereal seeds, and this review summarizes the current state of knowledge on the topic.

Prevalence of zoonotic trematodes in fish from a Vietnamese fish-farming community

The prevalence of fish-borne zoonotic trematode (FZT) metacercariae was investigated in fish farmed by rural households in Nghe An Province, located in northern Vietnam. In total, 716 fish, including tilapia (Oreochromis niloticus) and 6 carp species, i.e., grass carp (Ctenopharyngodon idellus), bighead carp (Aristichthys nobilis), mrigal (Cirrhinus mrigala), common carp (Cyprinus carpio), silver carp (Hypophthalmychthys molitrix), and roha (Labeo rohita), collected from 53 fish farms were examined. The overall prevalence of FZT metacercariae was 44.6%, ranging from 12.5% to 61.0% in fish species collected from grow-out ponds, which are the production system for growing fish from fingerling size to market size. The overall prevalence was 43.6% in fingerlings cultured in nurseries, ranging from 7.4% to 62.8% for different fish species. The FZT species recovered were heterophyids and echinostomatids and included Haplorchis pumilio, H. taichui, H. yokogawai, Centrocestus formosanus, Stellantchas musfalcatus, and Echinochasmus japonicus, all of which are intestinal flukes in humans, other mammals, and birds. This is the first report of H. yokogawai and E. japonicus in fish in Vietnam, and the first record for S. falcatus in northern Vietnam. Although a previous cross-sectional survey of the people living in these fish farm households revealed a very low prevalence of FZTs (< 1%), our results demonstrate that intestinal flukes are common in farmed fish in this area, suggesting that reservoir hosts such as dogs, cats, and pigs are more important in sustaining the life cycles of these flukes in fish farms than human hosts. This has implications for the effectiveness of control programs focused mainly on treatment of humans.

Electro-dewatering of sludge under pressure and non-pressure conditions

The electro-dewatering method is regarded as a promising approach to reduce the water content in sludge. Laboratory scale non-pressure and pressure-driven dewatering reactors were set up to study the dewatering rate in different types of sludge and the water content in the final sludge cake after electro-dewatering process. It was observed that in non-pressure experiments, the water removal rate was highly dependent on sludge pH buffering capacity and the type of sludge; the highest water removal rate (83.2 lm(-2) day(-1)) was achieved with anaerobic sludge. When pressure was applied, the rate of removal of water from the anode and the cathode depended on alkalinity as well as current density. During the electro-dewatering process, pressure had a significant contribution to water reduction in the final sludge cake in experiments using raw sludge and raw sludge with added alkalinity in comparison with non-pressure experiments using the same types of sludge. However, experiments using anaerobically digested sludge in non-pressure and pressure-driven reactors resulted in the same water content in the final sludge cake (40%). In general, different types of sludge with various amounts of alkalinity affected sludge electro-dewatering capacity by changing zeta potential and pH. Migration of negatively charged organic substances occurred during the applied low-level direct current (15 V), and chemical oxygen demand and total organic carbon concentrations in removed water were found to be higher at the anode and lower at the cathode in comparison with control experiments.

A shift in abscisic acid/gibberellin balance underlies retention of dormancy induced by seed development temperature

Through a combination of physiological, pharmacological, molecular and targeted metabolomics approaches, we showed that retention of wheat (Triticum aestivum L.) seed dormancy levels induced by low and high seed development temperatures during post-desiccation phases is associated with modulation of gibberellin (GA) level and seed responsiveness to abscisic acid (ABA) and GA via expression of TaABI5 and TaGAMYB, respectively. Dormancy retention during imbibition, however, is associated with modulations of both ABA level and responsiveness via expression of specific ABA metabolism (TaNCED2 and TaCYP707A1) and signalling (TaPYL2, TaSnRK2, TaABI3, TaABI4 and TaABI5) genes, and alterations of GA levels and responsiveness through expression of specific GA biosynthesis (TaGA20ox1, TaGA20ox2 and TaGA3ox2) and signalling (TaGID1 and TaGID2) genes, respectively. Expression patterns of GA signalling genes, TaRHT1 and TaGAMYB, lacked positive correlation with that of GA regulated genes and dormancy level observed in seeds developed at the two temperatures, implying their regulation at post-transcriptional level. Our results overall implicate that a shift in ABA/GA balance underlies retention of dormancy levels induced by seed development temperature during post-desiccation and imbibition phases. Consistently, genes regulated by ABA and GA during imbibition overlapped with those differentially expressed between imbibed seeds developed at the two temperatures and mediate different biological functions.

Using 320-slice computed tomography to preoperatively investigate the leg perforator arterial system and design a perforator flap for patients with a soft-tissue defect in the leg

PURPOSE

To investigate the leg perforator arterial system, identify the perforator flap's pedicle artery and its projected cutaneous point using a 320-slice computed tomography (CT 320) scanner.

METHODS

A total of 24 patients with leg soft-tissue defects unilaterally underwent 320-slice CT angiography scanning (CTA 320) with 47 legs. The used method enabled investigation of the perforator arteries originating from the tibial, peroneal arteries, perforator flap's pedicle artery and its projected cutaneous point. These data were used to preoperatively design an improved flap. Then, the CT-confirmed location and length of the flap's pedicle artery were compared with intraoperative findings.

RESULTS

Findings of the CTA 320 on 47 legs showed that 217 perforator arteries with diameters of ≥0.5mm were detected; the average number of arteries per leg, their average length and diameter were 4.6±2.1, 30.7±10.4mm and 1.16±0.27mm, respectively. The perforator arteries originating from the anterior tibial artery were mainly distributed in the proximal and middle thirds of the leg. Perforators from the posterior tibial and peroneal arteries were distributed abundantly in the middle and distal thirds of the leg. As identified in the CT, the location and length of the flap's pedicle artery and its projected cutaneous point were consistent with those observed during the surgery.

CONCLUSIONS

The CTA 320 is a minimally invasive imaging method that provides high-quality images of the leg perforator arterial system and can identify the exact location and projected cutaneous point of the perforator flap's pedicle artery.