OsDOF11 Affects Nitrogen Metabolism by Sucrose Transport Signaling in Rice (Oryza sativa L.)

Carbon and nitrogen antagonistically regulate multiple developmental processes. However, the molecular mechanism affecting nitrogen metabolism by sucrose transport remains poorly defined. Previously, we noted that Oryza sativa DNA BINDING WITH ONE FINGER 11 (OsDOF11) mediated sucrose transport by binding to the promoter regions of Sucrose Transporter 1 (SUT1), Oryza sativa Sugars Will Eventually be Exported Transporters 11 (OsSWEET11), and OsSWEET14. Here, we note that OsDOF11 promotes nitrogen uptake and then maintains the ratio of fresh weight to dry weight in seedling plants and the effective leaf blade at flowering stages. Mutants of the sucrose transporter gene OsSWEET14 displayed a phenotype similar to that of OsDOF11. By microarray analysis and qRT-PCR in OsDOF11 mutant plants, OsDOF11 affected the transcription level of amino acid metabolism-related genes. We further found that mainly amino acid contents were reduced in flag leaves but increased in seeds. Both sugar and organic nitrogen changes caused the ratio of fresh weight to dry weight to decrease in OsDOF11 mutant seedling plants and mature leaves, which might result in vigorous reduced metabolic activity and become less susceptible to stress. These results demonstrated that OsDOF11 affected nitrogen metabolism by sugar distribution in rice, which provided new insight that OsDOF11 coordinated with C and N balance to maintain plant growth activity.

Enhanced sucrose fermentation by introduction of heterologous sucrose transporter and invertase into Clostridium beijerinckii for acetone–butanol–ethanol production

A heterologous pathway for sucrose transport and metabolism was introduced into Clostridium beijerinckii to improve sucrose use for n -butanol production. The combined expression of StSUT1 , encoding a sucrose transporter from potato ( Solanum tuberosum ), and SUC2 , encoding a sucrose invertase from Saccharomyces cerevisiae , remarkably enhanced n -butanol production. With sucrose, sugarcane molasses and sugarcane juice as substrates, the C. beijerinckii strain harbouring StSUT1 and SUC2 increased acetone–butanol–ethanol production by 38.7%, 22.3% and 52.8%, respectively, compared with the wild-type strain. This is the first report to demonstrate enhanced sucrose fermentation due to the heterologous expression of a sucrose transporter and invertase in Clostridium . The metabolic engineering strategy used in this study can be widely applied in other microorganisms to enhance the production of high-value compounds from sucrose-based biomass.

Loading regulation prevents phloem failure during drought and widens the range of phloem and stomatal traits

Plant carbon transport is controlled by a multitude of parameters both internal and external to the sugar transporting phloem tissue. Sucrose transporter kinetics, conduit hydraulic resistance, and xylem water stress are all hypothesized to impact the amount of carbon delivered to sink tissues. However, the most important traits determining carbon export under drought are not well understood, especially for species with active molecular regulation of sucrose transport. This in turn limits our ability to assess species’ resistances to phloem dysfunction under drought. Here, we use an integrated xylem-phloem-stomatal model to calculate leaf water potential from soil dryness, which is then used to determine gas exchange and phloem pressure gradients. We quantitatively compare the impacts of phloem loading kinetics, including feedbacks between loading and phloem pressure, phloem conduit resistances, and stomatal responses to water stress, on the total carbon export to sinks during drought. Regulating sucrose transporter kinetics which downregulates loading at high phloem pressures prevented runaway viscosity in the phloem sap and was the most important determinant of export rates under drought. In contrast to previous models, we found this feedback mechanism decoupled stomatal traits from phloem export efficiency during drought and increased the operational range of phloem hydraulic resistances.

Arabidopsis Sucrose Transporter 4 (AtSUC4) is Involved in Root Response of High Content Sucrose-Growth Via IAA- and ABA- Dependent Manner

Source-to-sink transport of sucrose mediated by sucrose transporters (SUCs) is one of the major determinants of plant growth. However, the role of AtSUC4, the only member of Group IV sucrose transporter in Arabidopsis, was undervalued in sink organ during seedling period. In our study, the primary root length of the atsuc4 mutants was significantly longer than that of the wild-type (WT) under exogenous 4% and 6% sucrose treatment. But this phenotype could not be imitated by external application of glucose or mannitol. It means that the atsuc4 mutants were insensitive to high sucrose stress compared with WT. Meanwhile, HPLC-MS/MS results showed that the root of atsuc4 mutants accumulated less sucrose and ABA and more IAA content compared with WT on 4% and 6% sucrose supplementation. Transcriptome analysis showed that many key genes involved in IAA and ABA signals were respective stimulated and repressed in the atsuc4 mutants, respectively. Taken together, we concluded that the deficiency of AtSUC4, not only reducing the transported and uptaked of sucrose, but also as a signal, may be collaborated with IAA and ABA to regulate root growth under high sucrose stress. This study confirmed the new function of AtSUC4, and provided an promising candidate gene for improving tolerance to high sucrose stress.

Correction to: Characterization of a vacuolar sucrose transporter, HbSUT5, from Hevea brasiliensis: involvement in latex production through regulation of intracellular sucrose transport in the bark and laticifers

An amendment to this paper has been published and can be accessed via the original article.