Enhancing Sensitivity in Gas Detection: Porous Structures in Organic Field-Effect Transistor-Based Sensors.

Gas detection is crucial for detecting environmentally harmful gases. Organic field-effect transistor (OFET)-based gas sensors have attracted attention due to their promising performance and potential for integration into flexible and wearable devices. This review examines the operating mechanisms of OFET-based gas sensors and explores methods for improving sensitivity, with a focus on porous structures. Researchers have achieved significant enhancements in sensor performance by controlling the thickness and free volume of the organic semiconductor layer. Additionally, innovative fabrication techniques like self-assembly and etching have been used to create porous structures, facilitating the diffusion of target gas molecules, and improving sensor response and recovery. These advancements in porous structure fabrication suggest a promising future for OFET-based gas sensors, offering increased sensitivity and selectivity across various applications.

CRISPRi-Guided Metabolic Flux Engineering for Enhanced Protopanaxadiol Production in Saccharomyces cerevisiae.

Protopanaxadiol (PPD), an aglycon found in several dammarene-type ginsenosides, has high potency as a pharmaceutical. Nevertheless, application of these ginsenosides has been limited because of the high production cost due to the rare content of PPD in Panax ginseng and a long cultivation time (4-6 years). For the biological mass production of the PPD, de novo biosynthetic pathways for PPD were introduced in Saccharomyces cerevisiae and the metabolic flux toward the target molecule was restructured to avoid competition for carbon sources between native metabolic pathways and de novo biosynthetic pathways producing PPD in S. cerevisiae. Here, we report a CRISPRi (clustered regularly interspaced short palindromic repeats interference)-based customized metabolic flux system which downregulates the lanosterol (a competing metabolite of dammarenediol-II (DD-II)) synthase in S. cerevisiae. With the CRISPRi-mediated suppression of lanosterol synthase and diversion of lanosterol to DD-II and PPD in S. cerevisiae, we increased PPD production 14.4-fold in shake-flask fermentation and 5.7-fold in a long-term batch-fed fermentation.

ABA-insensitive3, ABA-insensitive5, and DELLAs Interact to activate the expression of SOMNUS and other high-temperature-inducible genes in imbibed seeds in Arabidopsis.

Seeds monitor the environment to germinate at the proper time, but different species respond differently to environmental conditions, particularly light and temperature. In Arabidopsis thaliana, light promotes germination but high temperature suppresses germination. We previously reported that light promotes germination by repressing SOMNUS (SOM). Here, we examined whether high temperature also regulates germination through SOM and found that high temperature activates SOM expression. Consistent with this, som mutants germinated more frequently than the wild type at high temperature. The induction of SOM mRNA at high temperature required abscisic acid (ABA) and gibberellic acid biosynthesis, and ABA-insensitive3 (ABI3), ABI5, and DELLAs positively regulated SOM expression. Chromatin immunoprecipitation assays indicated that ABI3, ABI5, and DELLAs all target the SOM promoter. At the protein level, ABI3, ABI5, and DELLAs all interact with each other, suggesting that they form a complex on the SOM promoter to activate SOM expression at high temperature. We found that high-temperature-inducible genes frequently have RY motifs and ABA-responsive elements in their promoters, some of which are targeted by ABI3, ABI5, and DELLAs in vivo. Taken together, our data indicate that ABI3, ABI5, and DELLAs mediate high-temperature signaling to activate the expression of SOM and other high-temperature-inducible genes, thereby inhibiting seed germination.

Two ginseng UDP-glycosyltransferases synthesize ginsenoside Rg3 and Rd.

Ginseng is a medicinal herb that requires cultivation under shade conditions, typically for 4-6 years, before harvesting. The principal components of ginseng are ginsenosides, glycosylated tetracyclic terpenes. Dammarene-type ginsenosides are classified into two groups, protopanaxadiol (PPD) and protopanaxatriol (PPT), based on their hydroxylation patterns, and further diverge to diverse ginsenosides through differential glycosylation. Three early enzymes, dammarenediol-II synthase (DS) and two P450 enzymes, protopanaxadiol synthase (PPDS) and protopanaxatriol synthase (PPTS), have been reported, but glycosyltransferases that are necessary to synthesize specific ginsenosides have not yet been fully identified. To discover glycosyltransferases responsible for ginsenoside biosynthesis, we sequenced and assembled the ginseng transcriptome de novo and characterized two UDP-glycosyltransferases (PgUGTs): PgUGT74AE2 and PgUGT94Q2. PgUGT74AE2 transfers a glucose moiety from UDP-glucose (UDP-Glc) to the C3 hydroxyl groups of PPD and compound K to form Rh2 and F2, respectively, whereas PgUGT94Q2 transfers a glucose moiety from UDP-Glc to Rh2 and F2 to form Rg3 and Rd, respectively. Introduction of the two UGT genes into yeast together with PgDS and PgPPDS resulted in the de novo production of Rg3. Our results indicate that these two UGTs are key enzymes for the synthesis of ginsenosides and provide a method for producing specific ginsenosides through yeast fermentation.

ABI3 and PIL5 collaboratively activate the expression of SOMNUS by directly binding to its promoter in imbibed Arabidopsis seeds.

A previous study showed that SOMNUS (SOM), which encodes a C3H-type zinc finger protein, is a key negative regulator of seed germination that acts downstream of PHYTOCHROME INTERACTING FACTOR3-LIKE5 (PIL5). However, it was not determined if PIL5 is the sole regulator of SOM expression. Public microarray data suggest that the expression of SOM mRNA is regulated also by ABSCISIC ACID INSENSITIVE3 (ABI3), another key regulator of seed germination. By analyzing abi3 mutants and ABI3 overexpression lines, we show here that ABI3 activates the expression of SOM mRNA collaboratively with PIL5 in imbibed seeds. Chromatin immunoprecipitation analysis coupled with electrophoretic mobility shift assay indicate that ABI3 activates the expression of SOM mRNA by directly binding to two RY motifs present in the SOM promoter in vivo, which is further supported by the greatly decreased expression of a reporter gene driven by a SOM promoter bearing mutated RY motifs. At the protein level, the ABI3 protein interacts with the PIL5 protein. The ABI3-PIL5 interaction, however, does not affect targeting of ABI3 and PIL5 to SOM promoters. Taken together, our results indicate that ABI3 and PIL5 collaboratively activate the expression of SOM mRNA by directly binding to and interacting with each other at the SOM promoter.

Identification of three groups of ginsenoside biosynthetic UDP-glycosyltransferases from Gynostemma pentaphyllum.

Ginsenosides are glycosylated dammarene-type triterpenes that have been identified in distantly related Panax ginseng and Gynostemma pentaphyllum. The phylogenetic relatedness of the ginsenoside biosynthetic genes in the two species was previously unknown. The final steps of ginsenoside biosynthesis are the glycosylations of hydroxylated triterpenes, protopanaxadiol (PPD) and protopanaxatriol (PPT), and their glycosylated forms by UDP-glycosyltransferases (UGTs). Ginsenoside biosynthetic UGTs have been identified in Panax but not in Gynostemma. Through a biochemical screening of Gynostemma UGTs (GpUGTs), we herein identified three groups of ginsenoside biosynthetic GpUGTs. These groups comprise: two GpUGTs that belong to the UGT71 family and glucosylate the C20-OH positions of PPD- and PPT-type ginsenosides; one GpUGT that belongs to the UGT74 family and glucosylates the C3-OH position of PPD-type ginsenosides; and two GpUGTs that belong to the UGT94 family and add a glucose to the C3-O-glucosides of PPD-type ginsenosides. These GpUGTs belong to the same UGT families as the ginsenoside biosynthetic Panax UGTs (PgUGTs). However, GpUGTs and PgUGTs belong to different subfamilies. Furthermore, cucumber UGTs orthologous to GpUGTs do not glucosylate ginsenosides. These results collectively suggest that, during evolution, P. ginseng and G. pentaphyllum independently opted to use the same UGT families to synthesize ginsenosides.

SOMNUS, a CCCH-type zinc finger protein in Arabidopsis, negatively regulates light-dependent seed germination downstream of PIL5.

Light absorbed by seed phytochromes of Arabidopsis thaliana modulates abscisic acid (ABA) and gibberellic acid (GA) signaling pathways at least partly via PHYTOCHROME-INTERACTING FACTOR3-LIKE5 (PIL5), a phytochrome-interacting basic helix-loop-helix transcription factor. Here, we report a new mutant, somnus (som), that germinates in darkness, independently of various light regimens. SOM encodes a nucleus-localized CCCH-type zinc finger protein. The som mutant has lower levels of ABA and elevated levels of GA due to expressional changes in ABA and GA metabolic genes. Unlike PIL5, however, SOM does not regulate the expression of GA-INSENSITIVE and REPRESSOR OF GA1 (RGA/RGA1), two DELLA genes encoding GA negative signaling components. Our in vivo analysis shows that PIL5 activates the expression of SOM by binding directly to its promoter, suggesting that PIL5 regulates ABA and GA metabolic genes partly through SOM. In agreement with these results, we also observed that the reduced germination frequency of a PIL5 overexpression line is rescued by the som mutation and that this rescue is accompanied by expressional changes in ABA and GA metabolic genes. Taken together, our results indicate that SOM is a component in the phytochrome signal transduction pathway that regulates hormone metabolic genes downstream of PIL5 during seed germination.