Search

In Hevea brasiliensis, an alkaline/neutral invertase ( A/ N-Inv) is responsible for sucrose catabolism in latex (essentially the cytoplasm of rubber-producing laticifers, the source of natural rubber) and implicated in rubber yield. However, neither the gene encoding this enzyme nor its molecular and biochemical properties have been well documented., Three Hevea A/ N-Inv genes, namely Hb NIN1, 2 and 3, were first cloned and characterized in planta and in Escherichia coli. Cellular localizations of Hb NIN2 m RNA and protein were probed. From latex, active A/ N-Inv proteins were purified, identified, and explored for enzymatic properties., Hb NIN2 was identified as the major A/ N-Inv gene functioning in latex based on its functionality in E. coli, its latex-predominant expression, the conspicuous localization of its m RNA and protein in the laticifers, and its expressional correlation with rubber yield. An active A/ N-Inv protein was partially purified from latex, and determined as Hb NIN2. The enhancement of Hb NIN2 enzymatic activity by pyridoxal is peculiar to A/ N-Invs in other plants., We conclude that Hb NIN2, a cytosolic A/ N-Inv, is responsible for sucrose catabolism in rubber laticifers. The results contribute to the studies of sucrose catabolism in plants as a whole and natural rubber synthesis in particular. [ABSTRACT FROM AUTHOR]

BackgroundViolence against doctors in China is a serious problem that has attracted attention from both domestic and international media. ObjectiveThis study investigates readers’ responses to media reports on violence against doctors to identify attitudes toward perpetrators and physicians and examine if such trends are influenced by national policies. MethodsWe searched 17 Chinese violence against doctors reports in international media sources from 2011 to 2020. We then tracked back the original reports and web crawled the 19,220 comments in China. To ascertain the possible turning point of public opinion, we searched violence against doctors–related policies from Tsinghua University ipolicy database from 2011 to 2020, and found 19 policies enacted by the Chinese central government aimed at alleviating the intense patient–physician relationship. We then conducted a series of interrupted time series analyses to examine the influence of these policies on public sentiment toward violence against doctors over time. ResultsThe interrupted time series analysis (ITSA) showed that the change in public sentiment toward violence against doctors reports was temporally associated with government interventions. The declarations of 10 of the public policies were followed by increases in the proportion of online public opinion in support of doctors (average slope changes of 0.010, P

Increasing demand for natural rubber prompts studies into the mechanisms governing the productivity of rubber tree (Hevea brasiliensis). It is very interesting to notice that a rubber tree of clone PR107 in Yunnan, China is reported to yield more than 20 times higher than the average rubber tree. This super-high-yielding (SHY) rubber tree (designated as SY107), produced 4.12 kg of latex (cytoplasm of rubber producing laticifers, containing about 30% of rubber) per tapping, more than 7-fold higher than that of the control. This rubber tree is therefore a good material to study how the rubber production is regulated at a molecular aspect. A comprehensive cDNA-AFLP transcript profiling was performed on the latex of SY107 and its average counterparts by using the 384 selective primer pairs for two restriction enzyme combinations (ApoI/MseI and TaqI/MseI). A total of 746 differentially expressed (DE) transcript-derived fragments (TDFs) were identified, of which the expression patterns of 453 TDFs were further confirmed by RT-PCR. These RT-PCR confirmed TDFs represented 352 non-redundant genes, of which 215 had known or partially known functions and were grouped into 10 functional categories. The top three largest categories were transcription and protein synthesis (representing 24.7% of the total genes), defense and stress (15.3%), and primary and secondary metabolism (14.0%). Detailed analysis of the DE-genes suggests notable characteristics of SHY phenotype in improved sucrose loading capability, rubber biosynthesis-preferred sugar utilization, enhanced general metabolism and timely stress alleviation. However, the SHY phenotype has little correlation with rubber-biosynthesis pathway genes. [ABSTRACT FROM AUTHOR]

Increasing demand for natural rubber prompts studies into the mechanisms governing the productivity of rubber tree (Hevea brasiliensis). It is very interesting to notice that a rubber tree of clone PR107 in Yunnan, China is reported to yield more than 20 times higher than the average rubber tree. This super-high-yielding (SHY) rubber tree (designated as SY107), produced 4.12 kg of latex (cytoplasm of rubber producing laticifers, containing about 30% of rubber) per tapping, more than 7-fold higher than that of the control. This rubber tree is therefore a good material to study how the rubber production is regulated at a molecular aspect. A comprehensive cDNA-AFLP transcript profiling was performed on the latex of SY107 and its average counterparts by using the 384 selective primer pairs for two restriction enzyme combinations (ApoI/MseI and TaqI/MseI). A total of 746 differentially expressed (DE) transcript-derived fragments (TDFs) were identified, of which the expression patterns of 453 TDFs were further confirmed by RT-PCR. These RT-PCR confirmed TDFs represented 352 non-redundant genes, of which 215 had known or partially known functions and were grouped into 10 functional categories. The top three largest categories were transcription and protein synthesis (representing 24.7% of the total genes), defense and stress (15.3%), and primary and secondary metabolism (14.0%). Detailed analysis of the DE-genes suggests notable characteristics of SHY phenotype in improved sucrose loading capability, rubber biosynthesis-preferred sugar utilization, enhanced general metabolism and timely stress alleviation. However, the SHY phenotype has little correlation with rubber-biosynthesis pathway genes. [ABSTRACT FROM AUTHOR]

• The latex has high gene expression specificity comparing with other tissues. • Natural rubber biosynthesis is a principal metabolic activity in latex. • Ubiquitin-proteasome system is a primary regulation system in latex. • Ethylene and jasmonate signaling pathways perform different functions in latex. Natural rubber, produced in the laticifers of the para rubber tree (Hevea brasiliensis), is a valuable biopolymer of commercial and strategic importance. While the basic pathway of rubber biosynthesis has been established, further understanding of its regulatory mechanisms might be obtained by studying laticifer-specific gene expression. Here, gene expression patterns was investigated in five different tissues of the rubber tree to explore differentially expressed genes (DEGs). The expression of 4122 high expression genes and 6485 low expression genes in the laticifer was enriched in various metabolic pathways related to rubber biosynthesis. The study results suggest that isopentenyl pyrophosphate (IPP), a principal precursor of natural rubber, is supplied mainly via the mevalonate (MVA) pathway in rubber biosynthesis, rather than the 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway. The ubiquitin-proteasome system (UBS) that is surprisingly active in the laticifer might serve as an important metabolic control mechanism in rubber biosynthesis. The involvement of latex specific transcription factors (TFs) was identified in seven plant hormone signal transductions, suggesting that jasmonate (JA) signaling is active in the positive regulation of rubber biosynthesis. [ABSTRACT FROM AUTHOR]

A novel method based on the monolithic column solid-phase extraction (SPE) coupled with high performance liquid chromatography in online mode was developed for the determination of trace forchlorfenuron in fruits. The enrichment factor of SPE for forchlorfenuron was 214. The method was fully validated. It showed a linear range of 0.01-50.00 microg/L and a limit of detection of 25 ng/L, with the relative standard deviation (RSD) of 3.9%. The proposed method was successfully applied for the determination of forchlorfenuron in grape, kiwifruit and watermelon samples, with the recoveries of 87.0%-120.7% and the RSDs of 0.6%-9.2%. This online method was proved to be selective, sensitive and convenient for the determination of trace forchlorfenuron in complex samples.

Gas chromatography (GC) is a widely used analytical technique in many fields. Sample preparation is very important in GC analysis due to its time consumed and deviations produced. In the present paper, the progress of some typical sample preparation techniques in gas chromatography, including purge and trap, solid phase extraction, solid phase microextraction, liquid phase microextraction, microwave assisted extraction, ultrasonic-assisted extraction, etc., are reviewed.