Engineering photo-methylotrophic Methylobacterium for enhanced 3-hydroxypropionic acid production during non-growth stage fermentation.

This study explored the potential of methanol as a sustainable feedstock for biomanufacturing, focusing on Methylobacterium extorquens, a well-established representative of methylotrophic cell factories. Despite this bacterium's long history, its untapped photosynthetic capabilities for production enhancement have remained unreported. Using genome-scale flux balance analysis, it was hypothesized that introducing photon fluxes could boost the yield of 3-hydroxypropionic acid (3-HP), an energy- and reducing equivalent-consuming chemicals. To realize this, M. extorquens was genetically modified by eliminating the negative regulator of photosynthesis, leading to improved ATP levels and metabolic activity in non-growth cells during a two-stage fermentation process. This modification resulted in a remarkable 3.0-fold increase in 3-HP titer and a 2.1-fold increase in its yield during stage (II). Transcriptomics revealed that enhanced light-driven methanol oxidation, NADH transhydrogenation, ATP generation, and fatty acid degradation were key factors. This development of photo-methylotrophy as a platform technology introduced novel opportunities for future production enhancements.

Phosphoribosylpyrophosphate synthetase as a metabolic valve advances Methylobacterium/Methylorubrum phyllosphere colonization and plant growth.

The proficiency of phyllosphere microbiomes in efficiently utilizing plant-provided nutrients is pivotal for their successful colonization of plants. The methylotrophic capabilities of Methylobacterium/Methylorubrum play a crucial role in this process. However, the precise mechanisms facilitating efficient colonization remain elusive. In the present study, we investigate the significance of methanol assimilation in shaping the success of mutualistic relationships between methylotrophs and plants. A set of strains originating from Methylorubrum extorquens AM1 are subjected to evolutionary pressures to thrive under low methanol conditions. A mutation in the phosphoribosylpyrophosphate synthetase gene is identified, which converts it into a metabolic valve. This valve redirects limited C1-carbon resources towards the synthesis of biomass by up-regulating a non-essential phosphoketolase pathway. These newly acquired bacterial traits demonstrate superior colonization capabilities, even at low abundance, leading to increased growth of inoculated plants. This function is prevalent in Methylobacterium/Methylorubrum strains. In summary, our findings offer insights that could guide the selection of Methylobacterium/Methylorubrum strains for advantageous agricultural applications.

Induced expression of DREB transcriptional factor and study on its physiological effects of drought tolerance in transgenic wheat.

Expression vector pBAC128F, which carries DREB transcriptional factor gene driven by drought inducing promoter rd29B and bar gene driven by CaMV 35S promoter and maize Adh1 gene first intron, was transferred into the explants of immature inflorescence and immature embryos of hexaploid winter wheat cv. 8901, 5-98, 99-92 and 104 by particle bombardment. More than 70 resistant transgenic plants were obtained. Genomic PCR and RNA dot blotting analyses showed that DREB gene had been integrated into wheat genome of the transgenic plants (T0 and T1) and was well expressed in offspring seed of different transgenic lines. The content of proline in leaves and seeds of T2 transgenic lines was analyzed. Among 16 tested transgenic lines, 10 transgenic lines exhibited more than two fold of proline level in leaves as compared with CK plants. Under drought condition, after stopping water for 15 days the leaves of transgenic lines were still green, while CK were faded. After rewatering for 10 days, the leaves of transgenic lines maintained their green, while all CK plants were dead. Our research suggested that introducing a novel DREB transcriptional factor into wheat is an effective way to improve its drought-tolerance ability.