SnRK1 phosphorylation of SDH positively regulates sorbitol metabolism and promotes sugar accumulation in peach fruit

Fruit quality depends largely on the type and amount of sugar accumulated in the fruit. In peach [Prunus persica (L.) Batsch], sorbitol is the main photosynthetic product and plays a crucial role in sugar metabolism. As a conserved energy sensor, SNF1-related kinase 1 (SnRK1) is involved in the regulation of carbon metabolism. In this study, SnRK1 was able to respond to induction by treatment with exogenous trehalose and sorbitol on 'Ruipan 17' peach fruit. After treatment with 100-mM trehalose for 3 h, the SnRK1 activity decreased by 18% and the activities of sorbitol dehydrogenase (SDH) and sucrose synthase (SS) also decreased significantly, but sucrose phosphate synthase (SPS) activity increased significantly; whereas sorbitol treatment under the same conditions resulted in a 12.6% increase in SnRK1 activity and the activities of SDH and SS synthase also increased significantly, compared with the control. The contents of glucose, fructose and sucrose in peach fruit increased significantly after 3 h of sorbitol treatment. In addition, the interactions between PpSnRK1α and enzymes PpSDH and PpSPS were confirmed by yeast two-hybrid method and the phosphorylation of PpSnRK1α and PpSDH was detected in vitro. Taken together, these results suggest that SnRK1 promotes sorbitol metabolism by activating SDH and it also regulates the activities of SS and SPS that enhance sucrose accumulation in peach fruit. SnRK1 protein kinase is involved in sugar metabolism and has the potential to be used for improving fruit quality.

Chicken cecal DNA methylome alteration in the response to Salmonella enterica serovar Enteritidis inoculation

BACKGROUND

Salmonella enterica serovar Enteritidis (SE) is one of the pathogenic bacteria, which affects poultry production and poses a severe threat to public health. Chicken meat and eggs are the main sources of human salmonellosis. DNA methylation is involved in regulatory processes including gene expression, chromatin structure and genomic imprinting. To understand the methylation regulation in the response to SE inoculation in chicken, the genome-wide DNA methylation profile following SE inoculation was analyzed through whole-genome bisulfite sequencing in the current study.

RESULTS

There were 185,362,463 clean reads and 126,098,724 unique reads in the control group, and 180,530,750 clean reads and 126,782,896 unique reads in the inoculated group. The methylation density in the gene body was higher than that in the upstream and downstream regions of the gene. There were 8946 differentially methylated genes (3639 hypo-methylated genes, 5307 hyper-methylated genes) obtained between inoculated and control groups. Methylated genes were mainly enriched in immune-related Gene Ontology (GO) terms and metabolic process terms. Cytokine-cytokine receptor interaction, TGF-beta signaling pathway, FoxO signaling pathway, Wnt signaling pathway and several metabolism-related pathways were significantly enriched. The density of differentially methylated cytosines in miRNAs was the highest. HOX genes were widely methylated.

CONCLUSIONS

The genome-wide DNA methylation profile in the response to SE inoculation in chicken was analyzed. SE inoculation promoted the DNA methylation in the chicken cecum and caused methylation alteration in immune- and metabolic- related genes. Wnt signal pathway, miRNAs and HOX gene family may play crucial roles in the methylation regulation of SE inoculation in chicken. The findings herein will deepen the understanding of epigenetic regulation in the response to SE inoculation in chicken.

Hyper-spectral response and estimation model of soil degradation in Kenli County, the Yellow River Delta

The ecological environment of the Yellow River Delta is fragile, and the soil degradation in the region is serious. Therefore it is important to discern the status of the soil degradation in a timely manner for soil conservation and utilization. The study area of this study was Kenli County in the Yellow River Delta of China. First, physical and chemical data of the soil were obtained by field investigations and soil sample analyses, and the hyper-spectra of air-dried soil samples were obtained via spectrometer. Then, the soil degradation index (SDI) was constructed by the key indicators of soil degradation, including pH, SSC, OM, AN, AP, AK, and soil texture. Next, according to a cluster analysis, soil degradation was divided into the following three grades: light degradation, moderate degradation, and heavy degradation. Moreover, the spectral characteristics of soil degradation were analyzed, and an estimation model of SDI was established by multiple stepwise regression. The results showed that the overall level of reflectance spectra increased with increased degree of soil degradation, that both derivative transformation and waveband reorganization could enhance the spectral information of soil degradation, and that the correlation between SDI and the spectral parameter of (R_λ2+R_λ1)/(R_λ2-R_λ1) was the highest among all the spectral parameters studied. On this basis, the optimum estimation model of SDI was established with the correlation coefficient of 0.811. This study fully embodies the potential of hyper-spectral technology in the study of soil degradation and provides a technical reference for the rapid extraction of information from soil degradation. Additionally, the study area is typical and representative, and thus can indirectly reflect the soil degradation situation of the whole Yellow River Delta.

Transcriptomic and phosphoproteomic profiling and metabolite analyses reveal the mechanism of NaHCO3-induced organic acid secretion in grapevine roots

BACKGROUND

Organic acid secretion is a widespread physiological response of plants to alkalinity. However, the characteristics and underlying mechanism of the alkali-induced secretion of organic acids are poorly understood.

RESULTS

Oxalate was the main organic acid synthesized and secreted in grapevine (a hybrid of Vitis amurensis, V. berlandieri and V. riparia) roots, while acetate synthesis and malate secretion were also promoted under NaHCO₃ stress. NaHCO₃ stress enhanced the H⁺ efflux rate of grapevine roots, which is related to the plasma membrane H⁺-ATPase activity. Transcriptomic profiling revealed that carbohydrate metabolism was the most significantly altered biological process under NaHCO₃ stress; a total of seven genes related to organic acid metabolism were significantly altered, including two phosphoenolpyruvate carboxylases and phosphoenolpyruvate carboxylase kinases. Additionally, the expression levels of five ATP-binding cassette transporters, particularly ATP-binding cassette B19, and two Al-activated malate transporter 2 s were substantially upregulated by NaHCO₃ stress. Phosphoproteomic profiling demonstrated that the altered phosphoproteins were primarily related to binding, catalytic activity and transporter activity in the context of their molecular functions. The phosphorylation levels of phosphoenolpyruvate carboxylase 3, two plasma membrane H⁺-ATPases 4 and ATP-binding cassette B19 and pleiotropic drug resistance 12 were significantly increased. Additionally, the inhibition of ethylene synthesis and perception completely blocked NaHCO₃-induced organic acid secretion, while the inhibition of indoleacetic acid synthesis reduced NaHCO₃-induced organic acid secretion.

CONCLUSIONS

Our results demonstrated that oxalate was the main organic acid produced under alkali stress and revealed the necessity of ethylene in mediating organic acid secretion. Additionally, we further identified several candidate genes and phosphoproteins responsible for organic acid metabolism and secretion.

Functional analysis of the GRMZM2G174449 promoter to identify Rhizoctonia solani-inducible cis-elements in maize

BACKGROUND

Banded leaf and sheath blight (BLSB), caused by the necrotrophic fungus Rhizoctonia solani, is a highly devastating disease in most maize and rice growing areas of the world. However, the molecular mechanisms of perceiving pathogen signals are poorly understood in hosts.

RESULTS

Here, we identified a Rhizoctonia solani-inducible promoter pGRMZM2G174449 in maize. Deletion analysis showed that the -574 to -455 fragment was necessary for pGRMZM2G174449 in responding to R. solani and this fragment contained the unknown pathogen-inducible cis-elements according to the bioinformatics analysis. Furthermore, detailed quantitative assays showed that two cis-elements, GCTGA in the -567 to -563 region and TATAT in the -485 to -481 region, were specifically responsible for the R. solani-inducible activity. A series of point mutation analysis indicated that the two cis-elements have the conserved motifs of NHWGN and DWYWT, respectively.

CONCLUSION

Our results indicated that pGRMZM2G174449 is a good R. solani-inducible promoter suitable for genetic engineering of BLSB resistance. And NHWGN and DWYWT are two R. solani-inducible cis-elements that play important roles in pGRMZM2G174449 responding to R. solani.

Impact of controlled release urea on maize yield and nitrogen use efficiency under different water conditions

Controlled release urea (CRU) has been widely adopted to increase nitrogen (N) use efficiency and maize production, but the impacts can range widely depending on water availability in the soil. In an experiment using Zhengdan 958 (a popular summer maize hybrid), three levels of water treatments (adequate water condition [W3], which maintained soil moisture at about 75% ± 5% of the soil’s field capacity; mild water stress [W2], which maintained moisture content at 55% ± 5% of field capacity; and severe water stress [W1], which had a moisture content of 35% ± 5% of field capacity) and four levels of controlled release urea fertilizer (N0, N1, N2 and N3 were 0, 105, 210 and 315 kg N ha^–1, respectively) were compared in a rainout shelter system with soil. The results revealed that CRU had significant effects on maize yields and N use efficiencies under different water conditions. The mean yields increased with increasing water levels and showed significant differences. Under W1, the accumulation of dry matter and N were limited, and N internal efficiency (NIE) and the apparent recovery efficiency of applied N (RE_N) decreased with N increases; yields of N1, N2, and N3 were similar. Under W2, the dry matter and N accumulation, as well as the yield, showed an increasing trend with an increase in N application, and the NIE and RE_N of N3 showed no difference from N2. Under W3, yields of N2 and N3 were similar and they were significantly higher than that of N1, but the agronomic N use efficiency (ANUE), RE_N, and the physiological NUE (PNUE) of N2 were 54.2, 34.9, and 14.4% higher, respectively, than those of N3. N application beyond the optimal N rate did not consistently increase maize yield, and caused a decrease in N use efficiencies. Highest overall dry matter, N accumulation, and yields were observed with N3 under W2, and those showed no differences with N2 and N3 under W3. Under this experimental condition, the CRU of 210 kg ha^–1 was optimized when soil moisture content was 75% ± 5% of field capacity, but an N rate of 315 kg ha^–1 was superior when soil moisture content during the entire growing season was maintained at 55% ± 5% of field capacity.