Arabidopsis PLANT U-BOX44 down-regulates osmotic stress signaling by mediating Ca2+-DEPENDENT PROTEIN KINASE4 degradation.

Calcium (Ca2+)-dependent protein kinases (CPKs) are essential regulators of plant responses to diverse environmental stressors, including osmotic stress. CPKs are activated by an increase in intracellular Ca2+ levels triggered by osmotic stress. However, how the levels of active CPK protein are dynamically and precisely regulated has yet to be determined. Here, we demonstrate that NaCl/mannitol-induced osmotic stress promoted the accumulation of CPK4 protein by disrupting its 26S proteasome-mediated CPK4 degradation in Arabidopsis (Arabidopsis thaliana). We isolated PLANT U-BOX44 (PUB44), a U-box type E3 ubiquitin ligase that ubiquitinates CPK4 and triggers its degradation. A calcium-free or kinase-inactive CPK4 variant was preferentially degraded compared to the Ca2+-bound active form of CPK4. Furthermore, PUB44 exhibited a CPK4-dependent negative role in the response of plants to osmotic stress. Osmotic stress induced the accumulation of CPK4 protein by inhibiting PUB44-mediated CPK4 degradation. The present findings reveal a mechanism for regulating CPK protein levels and establish the relevance of PUB44-dependent CPK4 regulation in modulating plant osmotic stress responses, providing insights into osmotic stress signal transduction mechanisms.

Comparative transcriptomic analysis of genes involved in stem lignin biosynthesis in woody and herbaceous Paeonia species.

Paeonia is recognized globally due to its ornamental value. However, the mechanisms behind the formation of distinct levels of lignification in Paeonia stems remain largely unknown. In this study, we selected three representative Paeonia species, namely P. ostii (shrub), P. lactiflora (herb), and P. × 'Hexie' (semi-shrub), to evaluate and contrast their respective anatomical structure, phytochemical composition and transcriptomic profile. Our results showed that the degree of lignin deposition on the cell wall, along with the total amount of lignin and its monomers (especially G-lignin) were higher in P. ostii stems compared to the other two species at almost all development stages except 80 days after flowering. Furthermore, we estimated a total number of unigenes of 60,238 in P. ostii, 43,563 in P. × 'Hexie', and 40,212 in P. lactiflora from stem transcriptome. We then built a co-expression network of 25 transcription factors and 21 enzyme genes involved in lignin biosynthesis and identified nine key candidate genes. The expression patterns of these genes were positively correlated with the transcription levels of PAL, C4H, 4CL2, CCR, and COMT, as well as lignin content. Moreover, the highest relative expression levels of CCR, 4CL2, and C4H were found in P. ostii. This study provides an explanation for the observed differences in lignification between woody and herbaceous Paeonia stems, and constitutes a novel reference for molecular studies of stem-specific lignification process and lignin biosynthesis that can impact the ornamental industry.

Ecotopic over-expression of PoCHS from Paeonia ostii altered the fatty acids composition and content in Arabidopsis thaliana.

Chalcone synthase (CHS) is the key enzyme in the flavonoid biosynthetic pathway and has been studied in many plants, but the function of the CHS gene has not been well characterized in Paeonia ostii. In this study, we obtained a CHS homolog gene from P. ostii, which possessed the putative conserved amino acids of chalcone synthase by multiple alignment analysis and demonstrated the highest expression in developing seeds. In vitro assays of the recombinant PoCHS protein confirmed enzymatic activity using malonyl-CoA and 4-coumaroyl-CoA as substrates, and the optimal pH and reaction temperature were 7.5 and 40 °C, respectively. Furthermore, ectopic over-expression of PoCHS in Arabidopsis up-regulated the expression levels of genes involved in seed development (ABI), glycolysis (PKp2, PDH-E1a, and SUS2/3), and especially fatty acid biosynthesis (BCCP2, CAC2, CDS2, FatA, and FAD3). This resulted in an increased unsaturated fatty acid content, especially α-linolenic acid, in transgenic Arabidopsis seeds. In this study, we examined the functions of CHS homolog of P. ostii and demonstrated its new function in seed fatty acid biosynthesis.

Online Quantitative Analysis of Chlorine Contents in Chlorinated Paraffins by Facile Raman Spectroscopy.

Online analysis of industrial chemicals is extremely important for managing product quality and performance. The chlorine (Cl) content is one of the most important technical metrics for chlorinated paraffins (CPs), and the conventional approaches to estimate Cl contents require transforming the Cl element to chloride followed by quantitative analysis with either titration or instrumentation, which are normally tedious and time-consuming and cannot simultaneously guide the industrial production. Here, we developed a rapid, real-time, and online approach to determine the Cl content of CPs with facile Raman spectroscopy. The chlorination of paraffins generated two new Raman peaks at 610-618 and 668-690 cm-1, which are associated with the vibrational modes of the SHH and SHC conformations of the C-Cl bond in CPs, respectively. More importantly, the corresponding peak of the SHH conformation decreased and that of the SHC conformation increased with the enhancement of the chlorination degree of CPs. The ratiometric calculation of the two respective Raman peak areas leads to a quantitative analysis of the Cl content of CPs. The developed approach can online provide the Cl contents of CPs within seconds accurately but without the tedious sample treatment required by conventional approaches. The strategy of integrating Raman analysis with the industrial pipeline will help in managing the production and quality control of industrial chemicals.

Contributions of species shade tolerance and individual light environment to photosynthetic induction in tropical tree seedlings.

It has long been debated whether tree leaves from shady environments exhibit higher photosynthetic induction efficiency (IE) than those from sunny environments and how the shade tolerance of tree species and the light environment of leaves contribute to the dynamics of photosynthesis. To address these questions, we investigated leaf photosynthetic responses to simulated changes of light intensity in seedlings of six tree species with differential shade tolerance. The seedlings were growing under different light environments in a lowland tropical forest. We proposed an index of relative shade tolerance (RST) to assess species-specific capacity to tolerate shade, and we quantified the light environment of individual leaves by the index of daily light integral (DLI), the averaged daily total light intensity. We obtained the following results. Photosynthetic IE, which is the ratio of the achieved carbon gain to the expected carbon gain, was significantly higher for species with a higher RST than for that with a lower RST. The impacts of light environment on the IE of individual leaves within the same species varied largely among different species. In the three species with relatively low RST, the IE of individual leaves decreased at higher DLIs when DLI < 10 mol m-2 d-1. Seedlings with high initial stomatal conductance before induction (gs50) possessed a higher IE than those with low gs50 from the same species. A trade-off existed between IE and steady-state photosynthetic rates. These results suggest a complex interaction between the shade tolerance of species and the light environments of individual leaves for photosynthetic induction and provide new insights into the adaptation strategy for understory seedlings under sunfleck environments.

ABSCISIC ACID-INSENSITIVE 5-ω3 FATTY ACID DESATURASE3 module regulates unsaturated fatty acids biosynthesis in Paeonia ostii.

Paeonia ostii is an authorized novel vegetable oil crop due to its seeds rich in unsaturated fatty acids (UFAs) especially α-linolenic acid (ALA), which overweight the current available edible oil. However, little is known on the regulation mechanism of UFAs biosynthesis during its seed development. Here, we used transcriptome and proteome data combining phytochemistry means to uncover the relationship between abscisic acid (ABA) signaling and UFAs biosynthesis during P. ostii seed development. Based on transcriptome and proteome analysis, two desaturases of omega-6 and omega-3 fatty acid, named as PoFAD2 and PoFAD3 responsible for ALA biosynthesis were identified. Then, an ABSCISIC ACID-INSENSITIVE 5 (ABI5) proteins was identified as an upstream transcriptional factor, which activated the expression of PoFAD3 instead of PoFAD2. Moreover, silencing of PoABI5 repressed the response of PoFAD3 to ABA. This study provides the first view on the connection between the function of ABA signaling factors and ALA biosynthesis in the P. ostii seed, which lays the foundation for studies on the regulatory mechanism of ABA signaling involved in the UFAs synthesis during seeds development, meanwhile, it will shed light on manipulation of ALA content for satisfying human demands on high quality of edible oil or healthy supplement.

Biomagnification of persistent organic pollutants along a high-altitude aquatic food chain in the Tibetan Plateau: Processes and mechanisms.

Biomagnification of some persistent organic pollutants (POPs) has been found in marine and freshwater food chains; however, due to the relatively short food chains in high-altitude alpine lakes, whether trophic transfer would result in the biomagnification of POPs is not clear. The transfer of various POPs, including organochlorine pesticides and polychlorinated biphenyls (PCBs), along the aquatic food chain in Nam Co Lake (4700 m), in the central Tibetan Plateau, was studied. The POPs levels in the water, sediment and biota [plankton, invertebrates and fish (Gymnocypris namensis)] of Nam Co were generally low, with concentrations comparable to those reported for the remote Arctic. The composition profiles of POPs in the fish were different from that in the water, but similar to their food. DDEs, DDDs, PCB 138, 153 and 180 displayed significant positive correlations with trophic levels, with trophic magnification factors (TMFs) ranged between 1.5 and 4.2, implying these chemicals can undergo final biomagnification along food chain. A fugacity-based dynamic bioaccumulation model was applied to the fish with localized parameters, by which the simulated concentrations were comparable to the measured data. Modeling results showed that most compounds underwent net gill loss and net gut uptake; only when the net result of the combined gut and gill fluxes would be positive, bioaccumulation could eventually occur. The net accumulation flux increased with fish age, which was caused by the continuous increase of gut uptake by aged fish. Due to the oligotrophic condition, efficient food absorption is likely the key factor that influences the gut POPs uptake. Long residence times with half-lives up to two decades were found for the higher chlorinated PCBs in Gymnocypris namensis.

[Enhancing effect of Tween 80 on degradation of triphenyltin by Bacillus thuringiensis].

So far, the information regarding enhanced degradation and biodegradation mechanisms of TPhT, an endocrine disruptor, is severely limited. Whether dearylation during TPhT degradation occurs successively or synchronously is not revealed clearly. To deal with these problems, this study focused on the biodegradation of TPhT and its metabolites by Bacillus thuringiensis through the acceleration of Tween 80. The results showed that Tween 80 obviously increased the TPhT solubility. After degradation by cells in the presence of 80 mg L-1 Tween 80 for 2 d, the residual TPhT at 1 mg L-1 initially was decreased to 48.4%. During the biodegradation process, Tween 80 significantly reduced intracellular Na+, NH+4: and Mg2+ release, and increased extracellular Cl- , PO(3-)4 and K+ utilization. Metabolites analysis revealed that phenyltin biodegradation initially proceeded by cleaving the aromatic ring, not by splitting the covalent bonds between the benzene rings and tin atom. Ring-cleavage reactions in the benzenes of TPhT occurred individually and synchronously, producing diphenyltin, monophenyltin and tin accordingly.