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Protein-based biorefining driven by nitrogen-responsive transcriptional machinery.

ABSTRACT: Background:Protein-based bioconversion has been demonstrated as a sustainable approach to produce higher alcohols and ammonia fertilizers. However, owing to the switchover from transcription mediated by the bacterial RNA polymerase ?70 to that mediated by alternative ? factors, the biofuel production driven by ?70-dependent promoters declines rapidly once cells enter the stationary phase or encounter stresses. To enhance biofuel production, in this study the growth phase-independent and nitrogen-responsive transcriptional machinery mediated by the ?54 is exploited to drive robust protein-to-fuel conversion. Results:We demonstrated that disrupting the Escherichia coli ammonia assimilation pathways driven by glutamate dehydrogenase and glutamine synthetase could sustain the activity of ?54-mediated transcription under ammonia-accumulating conditions. In addition, two ?54-dependent promoters, argTp and glnAp2, were identified as suitable candidates for driving pathway expression. Using these promoters, biofuel production from proteins was shown to persist to the stationary phase, with the net production in the stationary phase being 1.7-fold higher than that derived from the optimal reported ?70-dependent promoter P LlacO1. Biofuel production reaching levels 1.3- to 3.4-fold higher than those of the ?70-dependent promoters was also achieved by argTp and glnAp2 under stressed conditions. Moreover, the ?54-dependent promoters realized more rapid and stable production than that of ?70-dependent promoters during fed-batch fermentation, producing up to 4.78 g L?-?1 of total biofuels. Conclusions:These results suggested that the nitrogen-responsive transcriptional machinery offers the potential to decouple production from growth, highlighting this system as a novel candidate to realize growth phase-independent and stress-resistant biofuel production.

SUBMITTER: Ma L

PROVIDER: S-EPMC7045595 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Protein-based biorefining driven by nitrogen-responsive transcriptional machinery.

Ma Lianjie L Guo Liwei L Yang Yunpeng Y Guo Kai K Yan Yajun Y Ma Xiaoyan X Huo Yi-Xin YX

Biotechnology for biofuels 20200226

<h4>Background</h4>Protein-based bioconversion has been demonstrated as a sustainable approach to produce higher alcohols and ammonia fertilizers. However, owing to the switchover from transcription mediated by the bacterial RNA polymerase σ<sup>70</sup> to that mediated by alternative σ factors, the biofuel production driven by σ<sup>70</sup>-dependent promoters declines rapidly once cells enter the stationary phase or encounter stresses. To enhance biofuel production, in this study the growth ...[more]

PMID: 32127916

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Project description:Transcriptional activation in response to hypoxia in plants is orchestrated by ethylene-responsive factor group VII (ERF-VII) transcription factors, which are stable during hypoxia but destabilized during normoxia through their targeting to the N-end rule pathway of selective proteolysis. Whereas the conditionally expressed ERF-VII genes enable effective flooding survival strategies in rice, the constitutive accumulation of N-end-rule-insensitive versions of the Arabidopsis thaliana ERF-VII factor RAP2.12 is maladaptive. This suggests that transcriptional activation under hypoxia that leads to anaerobic metabolism may need to be fine-tuned. However, it is presently unknown whether a counterbalance of RAP2.12 exists. Genome-wide transcriptome analyses identified an uncharacterized trihelix transcription factor gene, which we named HYPOXIA RESPONSE ATTENUATOR1 (HRA1), as highly up-regulated by hypoxia. HRA1 counteracts the induction of core low oxygen-responsive genes and transcriptional activation of hypoxia-responsive promoters by RAP2.12. By yeast-two-hybrid assays and chromatin immunoprecipitation we demonstrated that HRA1 interacts with the RAP2.12 protein but with only a few genomic DNA regions from hypoxia-regulated genes, indicating that HRA1 modulates RAP2.12 through protein-protein interaction. Comparison of the low oxygen response of tissues characterized by different levels of metabolic hypoxia (i.e., the shoot apical zone versus mature rosette leaves) revealed that the antagonistic interplay between RAP2.12 and HRA1 enables a flexible response to fluctuating hypoxia and is of importance to stress survival. In Arabidopsis, an effective low oxygen-sensing response requires RAP2.12 stabilization followed by HRA1 induction to modulate the extent of the anaerobic response by negative feedback regulation of RAP2.12. This mechanism is crucial for plant survival under suboptimal oxygenation conditions. The discovery of the feedback loop regulating the oxygen-sensing mechanism in plants opens new perspectives for breeding flood-resistant crops.

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Protein-based biorefining driven by nitrogen-responsive transcriptional machinery.

Publications

Protein-based biorefining driven by nitrogen-responsive transcriptional machinery.

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