A Vacuolar Invertase CsVI2 Regulates Sucrose Metabolism and Increases Drought Tolerance in Cucumis sativus L.

Vacuolar invertase (VI) can irreversibly degrade sucrose into glucose and fructose and involve in plants abiotic-stress-tolerance. Cucumber (Cucumis sativus L.) is susceptible to drought stress, especially during the seedling stage. To date, the involvement of VI in drought tolerance in cucumber seedlings is in urgent need of exploration. In the present study, a cucumber vacuolar invertase gene, CsVI2, was isolated and functionally characterized. The results showed that (1) CsVI2 showed vacuolar invertase activity both in vivo and in vitro; (2) the transcript level of CsVI2, along with VI activity, was significantly induced by drought stress. Moreover, the expression of sucrose synthase 3 (CsSUS3) was increased and that of sucrose phosphate synthase 1 (CsSPS1) was decreased after exposure to drought stress, which was followed by an increase in sucrose synthase activity and a decrease in sucrose phosphate synthase activity; (3) CsVI2-overexpressing transformed cucumber seedlings showed enhanced vacuolar invertase activity and drought tolerance and 4) protein–protein interaction modelling indicated that a cucumber invertase inhibitor, CsINVINH3, can interact with CsVI2. In summary, the results indicate that CsVI2 as an invertase can regulate sucrose metabolism and enhance drought stress in cucumber seedlings.

The effects of straw-returning and inorganic K fertilizer on the carbon–nitrogen balance and reproductive growth of cotton

Background Many studies have indicated that straw-returning could meet part or even all of the potassium (K) demand for crop growth in the field, but few have compared the effects of crop straw as K source and inorganic K fertilizer on carbon–nitrogen (C–N) balance of cotton and the reproductive growth. To address this, field experiments were conducted using the cotton cultivar, Siza 3, under there treatments (CK as control group one, no crop straw and inorganic K fertilizer were applied; K150 as control group two, 150 kg·ha−1 of K2O was applied; and W9000, 9 000 kg·ha−1 wheat straw, which could provide K2O about 150 kg·ha−1, was incorporated into soil). Results Although the final reproductive organ biomass did not differ between W9000 and K150, W9000 had a higher ratio of reproductive organ biomass to total biomass (RRT), suggesting that straw-returning was more conducive to the allocation of biomass to reproductive organs. The theoretical maximum biomass of reproductive organ was higher, but the average and maximum accumulation rates of reproductive organ biomass were 2.8%∼8.3% and 2.5%∼8.2% lower under W9000 than K150. Also, the duration of rapid-accumulation period for reproductive organ biomass (T) was 2.0∼2.8 d longer under W9000 than K150, which was a reason for the higher RRT under W9000. Straw-returning altered the dynamics of leaf K with the growth period, so that W9000 had a more drastic effect on leaf C metabolism than K150. Consequently, lower soluble sugar/free amino acid and C/N ratios were measured under W9000 than K150 at boll-setting (BSS) and boll-opening (BOS) stages. Higher leaf net photosynthetic rate, sucrose phosphate synthase and sucrose synthase activities, and lower acid invertase activity were observed under W9000 than K150 at BSS and BOS and these were more conducive to sucrose accumulation. However, less sucrose was measured under W9000 than K150 at these stages. This should be because straw-returning promoted the assimilate transport capacity when compared with inorganic K fertilizer application, which also explained the higher RRT under W9000 than K150. The lower acid invertase activity under W9000 inhibited the conversion of sucrose to other sugars, hence lower contents of soluble sugar and starch were measured under W9000 than K150. Conclusion Under low K condition, crop straw as K source can increase the assimilate transport from source to sink, leading to lower C/N ratio in leaf and higher allocation of biomass to reproductive organs than inorganic K fertilizer.

Impacts of Fertilization Optimization on Ammonia Volatilization, Soil Nitrification, Denitration Intensity From Wheat Fields and Nitrogen Utilization Under Water-saving Irrigation

Scholars have proposed the practice of split N fertilizer application (SNFA), which has proven to be an effective approach for enhancing N use efficiency. However, the effect of SNFA on NH3 volatilization, nitrification and denitration in soil, remain largely unknown. As such, the current study assessed soil NH3 volatilization, nitrification and denitrification intensities, abundance of nitrogen cycle-related funetional genes, and invertase activity for different treatments. We applied a rate of 240 kg·ha-1 of N, and the following fertilizer ratios of the percent base to that of topdressing under water-saving irrigation: N1 (basal/dressing, 100%/0%), N2 (basal/dressing, 70%/30%), N3 (basal/dressing, 50%/50%), N4 (basal/dressing, 30%/70%), and N5 (basal/dressing, 0%/100%). N3 treatment resulted in a significant decrease in rate of NH3 volatilization. This treatment also significantly reduced nitrification and denitrification intensities, primarily owing to the reduced functional genes abundance involved in the nitrogen cycle (Amoa-AOB, nirK and nirS) and reduced invertase activity (urease, nitrate reductase, nitrite reductase) in wheat-land soil. 15N tracer studies further demonstrated that N3 treatments significantly increased the grain nitrogen accumulation by 9.50-28.27% compared with that under other treatments. This increase was primarily due to an increase in the amount of N absorbed by wheat from soil and fertilizers, which was caused by an enhancement in total N uptake (7.2-21.81%). Collectively, these results suggest that the N3 treatment (basal/dressing, 50%/50%) improves N uptake by wheat, reduces the soil NH3 volatilization rate, and has the potential to reduce the amount of N2O generated by nitrification and denitrification.

A New Approach for Determination of the Botanical Origin of Monofloral Bee Honey, Combining Mineral Content, Physicochemical Parameters, and Self-Organizing Maps

A new approach for the botanical origin determination of monofloral bee honey is developed. The methodology combines mineral content and physicochemical parameters determination with intelligent statistics such as self-organizing maps (SOMs). A total of 62 monofloral bee honey samples were analysed, including 31 linden, 14 rapeseed, 13 sunflower, and 4 acacia. All of them were harvested in 2018 and 2019 from trusted beekeepers, after confirming their botanical origin, using melissopalynological analysis. Nine physicochemical parameters were determined, including colour, water content, pH, electrical conductivity, hydroxymethylfurfural content, diastase activity, specific optical rotation, invertase activity, and proline. The content of thirty chemical elements (Ag, Al, As, B, Ba, Bi, Ca, Cd, Co, Cr, Cs, Cu, Fe, Ga, In, K, Li, Mg, Mn, Na, Ni, P, Pb, Rb, S, Se, Sr, Te, V, and Zn) was measured using ICP-OES, ICP-MS, and FAAS as instrumental techniques. The visualisation of the SOMs shows an excellent separation of honey samples in five well-defined clusters—linden, rapeseed, acacia, sunflower, and polyfloral honey—using the following set of 16 descriptors: diastase activity, hydroxymethylfurfural content, invertase activity, pH, specific optical rotation, water content, Al, B, Cr, Cs, K, Na, Ni, Rb, V, and Zn.

The main indicators of compliance with the production standards and storage conditions of honey

The study presents an updated database on the impact of the main technological factors on the content of pollen grains and quality indicators of natural honey: diastase number, hydroxymethylfurfural content and invertase activity. The purpose of the research was to update the database on the impact of the main technological factors on the microscopy and quality indicators of natural honey: diastase number, hydroxymethylfurfural content and invertase activity. Based on the goal, the following tasks were solved: On the basis of the laboratory of the FSC of Beekeeping, production samples of honey were heated at 75 °C for 10 minutes, followed by natural cooling, and filtered through a filter with a cell size of 0.15 mm; they were stored in the production room for a year with a temperature fluctuation in the range from –1 °C to 32 °C. The relevance of the study is to study the main indicator of the quality of honey – invertase activity, changes in the value under the influence of technological and zootechnical factors, with its subsequent introduction into the state standard for natural honey. The scientific novelty of the study lies in the fact that for the first time the values of invertase activity indicators, the content of hydroxymethylfurfural after heating and filtration of honey were obtained. Methods. The study of the indicators was carried out in accordance with the methods of the state standard GOST 19792-2017. As a result, it was found that heating honey at 75 °C for 10 minutes followed by natural cooling contributes to a decrease in diastase activity by an average of 69.7 ± 6.43 %, a decrease in invertase by an average of 81.0 ± 2.37 %, and an increase in the content of GMF by an average of 79.1 ± 1.74 %. Honey filtration reduces diastase by an average of 11.1 ± 1.47 %, and invertase activity by an average of 11.3 ± 2.34 %. Storage of honey for a year with a temperature fluctuation from –1 °C to 32 °C contributes to a decrease in the activity of diastase by 51.3 ± 5.27 %, invertase by 61.0 ± 1.91 % and an increase in the content of hydroxymethylfurfural by an average of 82.9 ± 1.80 %.

Honey Mead Fermentation from Thai Stingless Bee (Tetragonula leaviceps) Honey using Ethanol Tolerant Yeast

Honey mead is a well-known conventional alcoholic beverage made by microbial fermentation of diluted honey. The selection of prospective yeasts for inoculation of honey-must with regard to honey mead quality determines the quality of mead production. The yeast consortium tolerant to ethanol stress was selected for this study using an enrichment technique. The activity of the invertase enzyme and the level of ethanol tolerance have been investigated. Thai stingless bee honey was used as a substrate, and the selected ethanol tolerant yeast consortium was used for mead fermentation. The results revealed that the PP03 had the highest invertase activity of 75.13±9.16 U/mL and the highest ethanol tolerance level of 12%. This is the first study using an ethanol tolerant yeast consortium to ferment honey mead from Thai stingless bee honey.

Comparative study for obtaining inulinase and invertase by yeasts

The aim of this comparative study was to obtain a model for production of inulinase and invertase by species Saccharomyces, Candida and Hansenula, strains from culture collection of INCDCF-ICCF, using submerged fermentation in a medium containing inulin as source of C. This model explained the data variation and the actual relationships between the parameters and responses. The dry biomass content as well as the production of inulinase and invertase in the bioprocess medium was influenced by inulin concentration and microelement composition. The main parameters for bioprocesses were: inoculum size 2% (v/v), pH 6, temperature 280 C and 220 rpm agitation speed. Following comparative study for production of extracellular inulinase (exo and endo inulinase) and invertase were obtained for Candida arborea the best results, invertase production having significantly higher concentrations than inulinase (35.92 U/mL invertase activity vs. 8.01 U/mL inulinase activity), on M5 medium. These results could be useful for industrial applications such as food industry, pharmaceutical.

Enzyme preparation with hydrolytic action to intensify the fermentation process

В работе представлены результаты исследований ферментного препарата гидролитического действия, обладающего инвертазной активностью, синтезируемого промышленным штаммом Aspergillus niger Л-4 - продуцентом лимонной кислоты, - в условиях глубинной ферментации гидролизата кукурузного крахмала, в технологии хлебопечения с целью интенсификации процесса брожения. The paper presents the results of studies of the effect of an enzyme preparation of hydrolytic action with invertase activity, synthesized by the industrial strain Aspergillus niger L-4, a citric acid producer under conditions of deep fermentation of starch hydrolyzate, in baking technology in order to intensify the fermentation process.

Hexose translocation mediated by SlSWEET5b is required for pollen maturation in Solanum lycopersicum

Pollen fertility is critical for successful fertilization and, accordingly, for crop yield. While sugar unloading affects growth and development of all types of sink organs, the molecular nature for sugar import to tomato pollen is poorly understood. However, SWEET transporters have been proposed to function in pollen development. Here, qRT-PCR revealed that SlSWEET5b was markedly expressed in flowers when compared to the remaining tomato SlSWEETs; particularly, in the stamens of maturing flower buds undergoing mitosis. Distinct accumulation of SlSWEET5b-GUS fusion proteins was present in mature flower buds, especially in anther vascular and inner cells, symplasmic isolated pollen cells and styles. The demonstration that GFP fusion proteins located to the plasma membrane support the idea that the SlSWEET5b carrier functions in apoplasmic sugar translocation during pollen maturation. Such function is in line with data from yeast complementation experiments and radiotracer uptakes, showing that SlSWEET5b operates as a low affinity hexose-specific passive facilitator, with a KM of ~36 mM. Most importantly, RNAi-mediated suppression of SlSWEET5b expression resulted in shrunken nucleus-less pollen cells, impaired germination and low seed yield. Interestingly, stamens from SlSWEET5b-silenced tomato mutants contained significantly lower amounts of sucrose and increased invertase activity, pointing to reduced carbon supply and perturbed sucrose homeostasis in this tissue. Taken together, our findings reveal an essential role of SlSWEET5b in mediating apoplasmic hexose import into phloem unloading cells and into developing pollen cells to support pollen mitosis and maturation in tomato flowers.One-sentence SummaryPlasma-membrane-localized SlSWEET5b facilitates a sequential hexose flux, from phloem to anther cells and from anther locule to pollen, to support pollen maturation and fertility in tomato flowers.

Plasma membrane-localized SlSWEET7a and SlSWEET14 regulate sugar transport and storage in tomato fruits

Sugars, especially glucose and fructose, contribute to the taste and quality of tomato fruits. These compounds are translocated from the leaves to the fruits and then unloaded into the fruits by various sugar transporters at the plasma membrane. SWEETs, are sugar transporters that regulate sugar efflux independently of energy or pH. To date, the role of SWEETs in tomato has received very little attention. In this study, we performed functional analysis of SlSWEET7a and SlSWEET14 to gain insight into the regulation of sugar transport and storage in tomato fruits. SlSWEET7a and SlSWEET14 were mainly expressed in peduncles, vascular bundles, and seeds. Both SlSWEET7a and SlSWEET14 are plasma membrane-localized proteins that transport fructose, glucose, and sucrose. Apart from the resulting increase in mature fruit sugar content, silencing SlSWEET7a or SlSWEET14 resulted in taller plants and larger fruits (in SlSWEET7a-silenced lines). We also found that invertase activity and gene expression of some SlSWEET members increased, which was consistent with the increased availability of sucrose and hexose in the fruits. Overall, our results demonstrate that suppressing SlSWEET7a and SlSWEET14 could be a potential strategy for enhancing the sugar content of tomato fruits.