Gibberellins (GAs) are a class of important phytohormones regulating a variety of physiological processes during normal plant growth and development. One of the major events during GA-mediated growth is the degradation of DELLA proteins, key negative regulators of GA signaling pathway. The stability of DELLA proteins is thought to be controlled by protein phosphorylation and dephosphorylation. Up to date, no phosphatase involved in this process has been identified. We have identified a dwarfed dominant-negative Arabidopsis mutant, named topp4-1. Reduced expression of TOPP4 using an artificial microRNA strategy also resulted in a dwarfed phenotype. Genetic and biochemical analyses indicated that TOPP4 regulates GA signal transduction mainly via promoting DELLA protein degradation. The severely dwarfed topp4-1 phenotypes were partially rescued by the DELLA deficient mutants rga-t2 and gai-t6, suggesting that the DELLA proteins RGA and GAI are required for the biological function of TOPP4. Both RGA and GAI were greatly accumulated in topp4-1 but significantly decreased in 35S-TOPP4 transgenic plants compared to wild-type plants. Further analyses demonstrated that TOPP4 is able to directly bind and dephosphorylate RGA and GAI, confirming that the TOPP4-controlled phosphorylation status of DELLAs is associated with their stability. These studies provide direct evidence for a crucial role of protein dephosphorylation mediated by TOPP4 in the GA signaling pathway.

Background Food safety has long been the subject of scholarly research, and street food is a weak link in food safety supervision. Street food not only provides convenience for many people, but is also the livelihood for millions of low income people, making a great contribution to the economy of many developing countries. Methods Street food safety is essential, and yet it has been rarely studied in China. Therefore, a typical city in China was selected as the research object to assess food safety knowledge, attitudes, and street food suppliers and consumer behaviors using questionnaires based on previous studies, and considering China’s particular characteristics and reasonable impacts identified in previous studies, such as increased income, work experience, licenses, and locations. The food safety knowledge and attitude questionnaire conformed with the national conditions in China. It was used to assess the food safety knowledge and attitudes toward food suppliers and consumers, where three main areas were addressed in the surveys and statistical analysis, as follows. (1) Statistical information including gender, age, education, income, food safety training, and specific elements related to the work experience of suppliers. (2) Knowledge of food safety including the awareness of consumers and suppliers regarding food poisoning pathogens, food and personal hygiene, high-risk groups, and correct cleaning. (3) A list of food handling behaviors was used to determine the behaviors and characteristics of subjects. Results The results show that street food suppliers have generally poor food handling practices, and most are operating under unsanitary conditions. Food safety knowledge of street vendors in the High-tech Industries Development Zone was the lowest, most likely because these regions are located in rural-urban fringe zones, where education levels are generally relatively low. Food safety attitudes of the youngest consumers were significantly better than those of older age groups. Their educational level was also different, with correspondingly relatively high income for younger individuals. Most vendors chose locations near schools or supermarkets. Consumers and street food vendors had good understanding of food safety, but street vendors were relatively poor in carrying out safe food handling, with only 26.7% using or being fully equipped withhand-washing facilities, although more than 60% of vendors wore clean and tidy clothes and masks. Conclusions Street food vendor training should be prioritized to improve the safety of street food. Other policies and measures should also be propagated to improve the food safety knowledge, attitudes, and behavior of vendors in Handan. Steps should be taken to improve street food stall operating conditions and facilities, including providing clean protected structures, access to potable water, and efficient waste collection and disposal systems. These findings shoul...

Dihydroflavonol 4-reductase (DFR, EC 1.1.1.219) is a rate-limited enzyme in the biosynthesis of anthocyanins and condensed tannins (proanthocyanidins) that catalyzes the reduction of dihydroflavonols to leucoanthocyanins. In this study, two full-length transcripts encoding for PtrDFR1 and PtrDFR2 were isolated from Populus trichocarpa. Sequence alignment of the two PtrDFRs with other known DFRs reveals the homology of these genes. The expression profile of PtrDFRs was investigated in various tissues of P. trichocarpa. To determine their functions, two PtrDFRs were overexpressed in tobacco (Nicotiana tabacum) via Agrobacterium-mediated transformation. The associated color change in the flowers was observed in all 35S:PtrDFR1 lines, but not in 35S:PtrDFR2 lines. Compared to the wild-type control, a significantly higher accumulation of anthocyanins was detected in transgenic plants harboring the PtrDFR1. Furthermore, overexpressing PtrDFR1 in Chinese white poplar (P. tomentosa Carr.) resulted in a higher accumulation of both anthocyanins and condensed tannins, whereas constitutively expressing PtrDFR2 only improved condensed tannin accumulation, indicating the potential regulation of condensed tannins by PtrDFR2 in the biosynthetic pathway in poplars.

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SummaryA chloroplast-localized tetratricopeptide repeat-containing protein, SG1, was identified through a slow-greening mutant in Arabidopsis. SG1 is required for proplastid to chloroplast transition and its mutation disrupted the transcriptions of chloroplast-related genes. It also genetically interacts with GUN1 or GUN4.