The BTB-BACK-TAZ domain protein MdBT2 reduces drought resistance by weakening the positive regulatory effect of MdHDZ27 on apple drought tolerance via ubiquitination.

Drought stress is one of the dominating challenges to the growth and productivity in crop plants. Elucidating the molecular mechanisms of plants responses to drought stress is fundamental to improve fruit quality. However, such molecular mechanisms are poorly understood in apple (Malus domestica Borkh.). In this study, we explored that the BTB-BACK-TAZ protein, MdBT2, negatively modulates the drought tolerance of apple plantlets. Moreover, we identified a novel Homeodomain-leucine zipper (HD-Zip) transcription factor, MdHDZ27, using a yeast two-hybrid (Y2H) screen with MdBT2 as the bait. Overexpression of MdHDZ27 in apple plantlets, calli, and tomato plantlets enhanced their drought tolerance by promoting the expression of drought tolerance-related genes [responsive to dehydration 29A (MdRD29A) and MdRD29B]. Biochemical analyses demonstrated that MdHDZ27 directly binds to and activates the promoters of MdRD29A and MdRD29B. Furthermore, in vitro and in vivo assays indicate that MdBT2 interacts with and ubiquitinates MdHDZ27, via the ubiquitin/26S proteasome pathway. This ubiquitination results in the degradation of MdHDZ27 and weakens the transcriptional activation of MdHDZ27 on MdRD29A and MdRD29B. Finally, a series of transgenic analyses in apple plantlets further clarified the role of the relationship between MdBT2 and MdHDZ27, as well as the effect of their interaction on drought resistance in apple plantlets. Collectively, our findings reveal a novel mechanism by which the MdBT2-MdHDZ27 regulatory module controls drought tolerance, which is of great significance for enhancing the drought resistance of apple and other plants.

In Situ Generation of AgI Quantum Dots by the Confinement of A Supramolecular Polymer Network: A Novel Approach for Ultrasensitive Response.

A novel approach for in situ generation of AgI quantum dots by the confinement of a pillar[5]arene-based supramolecular polymer network has been successfully developed. The supramolecular polymer network (SPN-QP) was constructed by using a bis-8-hydroxyquinoline-modified pillar[5]arene derivative as a host (H-QP) and a bis-pyridinium-modified decane as guest (G-PD). The SPN-QP shows ultrasensitive response for Ag+ . The limit of detection is about 7.44×10-9  M.. Interestingly, when I- was added to the SPN-QP+Ag+ system, an unexpected strong warm-white fluorescence emission was observed. After carefu investigation, we found that the strong warm-white fluorescence emission could be attributed to the in situ formation of AgI quantum dots under the confinement of the supramolecular polymer network (SPN-QP). Based on this approach, ultrasensitive detection of I- was realized. The limit of detection for I- is 4.40×10-9  M. This study provides a new way for the preparation of quantum dots under the confinement of supramolecular polymer network as well as ultrasensitive detection of ions by in situ formation of quantum dots.

Novel pillar[5]arene-based supramolecular organic framework gel for ultrasensitive response Fe3+ and F- in water.

A novel supramolecular organic framework gel (PQPA) has been constructed by a novel bilateral 8-hydroxyquinoline modified pillar[5]arene host (P5Q) and a bilateral bromohexyl functionalized pillar[5]arene guest (P5C6). Interestingly, the gel PQPA shows special selective and ultrasensitive sensing property for Fe3+. The limit of lowest detection (LOD) of gel PQPA for Fe3+ is 0.102 nM. Meanwhile, by adding Fe3+ into the gel PQPA, a no fluorescence Fe3+ coordinated metallogel (PQPA-Fe) could be constructed. Due to the competitive coordination of F-, fluorescent "turn-on" ultrasensitive response of the Fe3+ coordinated metallogel (PQPA-Fe) for F- is achieved. The limit of lowest detection of the Fe3+ coordinated metallogel (PQPA-Fe) for F- is 9.79 nM. In addition, the xerogel of the supramolecular organic framework gel (PQPA) is capable for removing Fe3+ in a lower concentration aqueous solution at an adsorption rate of 99.9%. More importantly, the supramolecular organic framework gel (PQPA) could be used to detect Fe3+ in the Yellow River Water samples. The supramolecular organic framework gel (PQPA) and Fe3+ coordinated metallogel (PQPA-Fe) could act as ultrasensitive reversible fluorescent chemosensor, test kits and fluorescent display materials for Fe3+ and F-.

Multi-stimuli-responsive supramolecular gel constructed by pillar[5]arene-based pseudorotaxanes for efficient detection and separation of multi-analytes in aqueous solution.

Here, a novel pseudorotaxanes-type crosslinker of a supramolecular polymer network (WP5-PN) has been constructed from a host water-soluble pillar[5]arene (WP5) and a guest naphthalene dimethylamine derivative (PN) via a stepwise process involving multiple non-covalent interactions. The obtained supramolecular polymers were able to transform into a supramolecular polymer gel (WP5-PN-G) and show AIE properties in DMSO-H2O binary solution. Interestingly, due to the dynamic and reversible nature of non-covalent interactions, the resultant supramolecular polymer gels exhibited external stimuli-responsiveness to different parameters, such as temperature, acid-base, competitive guest and mechanical stress. Moreover, WP5-PN-G showed fluorescent response for Fe3+ and Cu2+, while its xerogel showed excellent recyclable separation properties for these metal ions with adsorption rates up to 98.07% and 95.38%, respectively. Moreover, by rational introduction of these metal ions into the WP5-PN-G, corresponding metal ion coordinated metallogels, such as WP5-PN-FeG and WP5-PN-CuG were obtained. These metallogels could selectively and sensitively sense F- and CN-, respectively. The detection limits of these metallogels for F- and CN- were about 1 × 10-8 M. The WP5-PN-G has potential applications in multi-analytes detection and separation as well as fluorescent display materials.

[Study on the use of ultrasound technique in extraction of polysaccharides from Loquat leaf].

In order to gain the optimal extract condition of extraction polysaccharides in Loquate leaf by ultrasound technique, the single factor and the orthogonal experiments were carried. The results showed that the optimal condition turned out to be ultrasound extraction time 35 min, ultrasound power 120W, extraction temperature 60 degrees C and the liquid-to-solid ratio 12: 1. In contrast to conventional extraction method, the ultrasound technique could be a better method for extracting the polysaccharides from Loquat leaf with a higher yield and shorter time.