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SUMMARY: 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. Significance Statement: Collectively, our findings clearly decipher a novel regulatory network for drought tolerance in the apple plant, which centers on the regulatory module MdBT2‐MdHDZ27 and its roles in transcriptional regulation and post‐transcriptional modification, which will be useful for improving the drought tolerances of apple and other economically important plant species. [ABSTRACT FROM AUTHOR]

A supramolecular sensor (APRA–G) was successfully constructed via host–guest interactions between a rhodamine hydrazone functionalized pillar[5]arene (APRA) and a bis-pyridinium derivative (G), which showed highly selective and sensitive detection of toxic Hg2+ through a dual-channel (colorimetric and fluorescent) model. The detection limits of fluorescence and UV-vis spectroscopy towards Hg2+ were 1.69 × 10−8 M and 4.07 × 10−7 M, respectively, which were calculated using the 3σ method. Interestingly, APRA–G could act as an excellent material for Hg2+ separation. Based on ICP (including inductively coupled plasma) data, the separation percentage of the supramolecular sensor (APRA–G) for mercury ions was up to 99.68%. [ABSTRACT FROM AUTHOR]

A supramolecular sensor (APRA–G) was successfully constructed via host–guest interactions between a rhodamine hydrazone functionalized pillar[5]arene (APRA) and a bis-pyridinium derivative (G), which showed highly selective and sensitive detection of toxic Hg2+ through a dual-channel (colorimetric and fluorescent) model. The detection limits of fluorescence and UV-vis spectroscopy towards Hg2+ were 1.69 × 10−8 M and 4.07 × 10−7 M, respectively, which were calculated using the 3σ method. Interestingly, APRA–G could act as an excellent material for Hg2+ separation. Based on ICP (including inductively coupled plasma) data, the separation percentage of the supramolecular sensor (APRA–G) for mercury ions was up to 99.68%. [ABSTRACT FROM AUTHOR]

A novel supramolecular polymer metallogel (QP5‐AlG) has been constructed by cross‐linking of bis‐8‐hydroxyquinoline functionalized pillar[5]arene with Al3+. The metallogel QP5‐AlG shows light blue aggregation induced emission (AIE) in DMSO/H2O binary solution. Interestingly, the QP5‐AlG shown multiple external stimuli‐responsive behaviors such as temperature, guest compounds, acid, base and so on. The QP5‐AlG can be used as a fluorescent material for detection of Fe3+, F‐, trifluoroacetic acid (TFA) and triethylamine (TEA) by different fluorescence states ("on" or "off"). The (limits of lowest detection) LOQs of the QP5‐AlG for Fe3+, F‐, TFA and TEA are in the range of 4.39 × 10‐9‐1.82 × 10‐7 M. More interestingly, a QP5‐AlG‐based rewritable and erasable fluorescent platform was demonstrated, which offers a potential testbed for performing "write‐erase‐write" cycles multiple times. This study provides insight into the development of novel multifunctional supramolecular materials. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A highly efficient supramolecular sensor based on 2-(hydroxy)-naphthyl imino-functionalized pillar[5]arene (AP5N) for the tandem fluorescence detection of Fe3+ and F− in H2O/DMSO (1/9, v/v) solution was successfully synthesized. On addition of Fe3+ to AP5N, the blue fluorescence was quenched. The detection limit of fluorescence for Fe3+ was estimated to be 1.21 × 10−7 M with short detection duration. Moreover, the AP5N–Fe3+ complex could selectively exhibit “turn-on” fluorescence on sensing F− (LOD = 1.34 × 10−7 M). In addition, the sensor AP5N could separate Fe3+ from aqueous solution with excellent ingestion capacity, and the Fe3+ separation rate was up to 98.25%. Moreover, the fluorescence changes of AP5N upon addition of Fe3+ and F− could be utilized as an IMPLICATION logic gate. Furthermore, as a practical application, ion test strips based on AP5N were fabricated, which can act as convenient and efficient test kits for detecting Fe3+ and F−. [ABSTRACT FROM AUTHOR]

A highly efficient supramolecular sensor based on 2-(hydroxy)-naphthyl imino-functionalized pillar[5]arene (AP5N) for the tandem fluorescence detection of Fe3+ and F− in H2O/DMSO (1/9, v/v) solution was successfully synthesized. On addition of Fe3+ to AP5N, the blue fluorescence was quenched. The detection limit of fluorescence for Fe3+ was estimated to be 1.21 × 10−7 M with short detection duration. Moreover, the AP5N–Fe3+ complex could selectively exhibit “turn-on” fluorescence on sensing F− (LOD = 1.34 × 10−7 M). In addition, the sensor AP5N could separate Fe3+ from aqueous solution with excellent ingestion capacity, and the Fe3+ separation rate was up to 98.25%. Moreover, the fluorescence changes of AP5N upon addition of Fe3+ and F− could be utilized as an IMPLICATION logic gate. Furthermore, as a practical application, ion test strips based on AP5N were fabricated, which can act as convenient and efficient test kits for detecting Fe3+ and F−. [ABSTRACT FROM AUTHOR]