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SUMMARY: Pustule formation is pivotal for the development of the Xanthomonas citri subsp. citri (Xcc)‐induced citrus canker disease (CCD). Although our previous study demonstrated that the exogenous application of abscisic acid (ABA) facilitated pustule formation induced by Xcc, the precise mechanism remains elusive. The 9‐cis‐epoxycarotenoid dioxygenase (NCED) is a crucial enzyme in ABA biosynthesis. This study explored the role of citrus CsNCED1‐1 in CCD resistance through overexpression and RNA interference of CsNCED1‐1 in Wanjincheng orange (Citrus sinensis). Our findings indicated that CsNCED1‐1 negatively modulated CCD resistance by fostering ABA accumulation, concomitant with an increase in jasmonic acid (JA) and a decrease in salicylic acid (SA). Plants overexpressing CsNCED1‐1 displayed shortened leaves with smaller and denser stomata along with irregular and increased palisade cells. CsLOB1 is a known susceptibility gene for CCD, and CsbZIP40 positively influences resistance to this disease. We further confirmed that CsLOB1 promoted and CsbZIP40 suppressed the transcription of CsNCED1‐1 by directly binding to the CsNCED1‐1 promoter. Notably, CsbZIP40 and CsLOB1 showed a competitive relationship in the regulation of CsNCED1‐1 expression, with CsbZIP40 exhibiting greater competitiveness. Overall, our findings highlight that CsNCED1‐1 promotes susceptibility to citrus canker by disrupting JA‐ and SA‐mediated defense mechanisms and triggering the proliferation and remodeling of palisade cells, thereby facilitating pathogen colonization and pustule formation. This study offers novel insights into the regulatory mechanisms underlying citrus canker resistance and the role of CsNCED1‐1 in citrus. [ABSTRACT FROM AUTHOR]

Citrus bacterial canker (CBC) is a disease that poses a major threat to global citrus production and is caused by infection with Xanthomonas citri subsp. citri (Xcc). Wall-associated receptor-like kinase (WAKL) proteins play an important role in shaping plant resistance to various bacterial and fungal pathogens. In a previous report, CsWAKL01 was identified as a candidate Xcc -inducible gene found to be up-regulated in CBC-resistant citrus plants. However, the functional role of CsWAKL01 and the mechanisms whereby it may influence resistance to CBC have yet to be clarified. Here, CsWAKL01 was found to localize to the plasma membrane, and the overexpression of the corresponding gene in transgenic sweet oranges resulted in pronounced enhancement of CBC resistance, whereas its knockdown had the opposite effect. Mechanistically, the effect of CsWAKL01 was linked to its ability to reprogram jasmonic acid, salicylic acid, and abscisic acid signaling activity. CsWRKY53 was further identified as a transcription factor capable of directly binding to the CsWAKL01 promoter and inducing its transcriptional up-regulation. CsWRKY53 silencing conferred greater CBC susceptibility to infected plants. Overall, these data support a model wherein CsWRKY53 functions as a positive regulator of CsWAKL01 to enhance resistance to CBC via the reprogramming of phytohormone signaling. Together these results offer new insights into the mechanisms whereby WAKLs shape phytopathogen resistance while underscoring the potential value of targeting the CsWRKY53–CsWAKL01 axis when seeking to breed CBC-resistant citrus plant varieties. [ABSTRACT FROM AUTHOR]

SUMMARY: Citrus bacterial canker (CBC) is a serious bacterial disease caused by Xanthomonas citri subsp. citri (Xcc) that adversely impacts the global citrus industry. In a previous study, we demonstrated that overexpression of an Xcc‐inducible apetala 2/ethylene response factor encoded by Citrus sinensis, CsAP2‐09, enhances CBC resistance. The mechanism responsible for this effect, however, is not known. In the present study, we showed that CsAP2‐09 targeted the promoter of the Xcc‐inducible WRKY transcription factor coding gene CsWRKY25 directly, activating its transcription. CsWRKY25 was found to localize to the nucleus and to activate transcriptional activity. Plants overexpressing CsWRKY25 were more resistant to CBC and showed higher expression of the respiratory burst oxidase homolog (RBOH) CsRBOH2, in addition to exhibiting increased RBOH activity. Transient overexpression assays in citrus confirmed that CsWRKY25 and CsRBOH2 participated in the generation of reactive oxygen species (ROS) bursts, which were able to restore the ROS degradation caused by CsAP2‐09 knockdown. Moreover, CsWRKY25 was found to bind directly to W‐box elements within the CsRBOH2 promoter. Notably, CsRBOH2 knockdown had been reported previously to reduce the CBC resistance, while demonstrated in this study, CsRBOH2 transient overexpression can enhance the CBC resistance. Overall, our results outline a pathway through which CsAP2‐09‐CsWRKY25 transcriptionally reprograms CsRBOH2‐mediated ROS homeostasis in a manner conducive to CBC resistance. These data offer new insight into the mechanisms and regulatory pathways through which CsAP2‐09 regulates CBC resistance, highlighting its potential utility as a target for the breeding of CBC‐resistant citrus varieties. Significant Statement: In the present study, we identify a pathway in which CsAP2‐09 and CsWRKY25 form a transcription factor cascade, transcriptionally reprogramming CsRBOH2‐mediated reactive oxygen species homeostasis and citrus bacterial canker (CBC) resistance. Our study explores new insights into the mechanistic role of CsAP2‐09 and the associated regulatory network, extending the potential value of CsAP2‐09 in the breeding of CBC‐tolerant citrus plants. [ABSTRACT FROM AUTHOR]

Citrus bacterial canker (CBC) is a severe bacterial infection caused by Xanthomonas citri subsp. citri (Xcc), which continues to adversely impact citrus production worldwide. Members of the GATA family are important regulators of plant development and regulate plant responses to particular stressors. This report aimed to systematically elucidate the Citrus sinensis genome to identify and annotate genes that encode GATAs and evaluate the functional importance of these CsGATAs as regulators of CBC resistance. In total, 24 CsGATAs were identified and classified into four subfamilies. Furthermore, the phylogenetic relationships, chromosomal locations, collinear relationships, gene structures, and conserved domains for each of these GATA family members were also evaluated. It was observed that Xcc infection induced some CsGATAs, among which CsGATA12 was chosen for further functional validation. CsGATA12 was found to be localized in the nucleus and was differentially upregulated in the CBC-resistant and CBC-sensitive Kumquat and Wanjincheng citrus varieties. When transiently overexpressed, CsGATA12 significantly reduced CBC resistance with a corresponding increase in abscisic acid, jasmonic acid, and antioxidant enzyme levels. These alterations were consistent with lower levels of salicylic acid, ethylene, and reactive oxygen species. Moreover, the bacteria-induced CsGATA12 gene silencing yielded the opposite phenotypic outcomes. This investigation highlights the important role of CsGATA12 in regulating CBC resistance, underscoring its potential utility as a target for breeding citrus varieties with superior phytopathogen resistance. [ABSTRACT FROM AUTHOR]

With the development of organic solar cells (OSCs), the high‐performance and stable batch variance are becoming a new challenge for designing polymer donors. To obtain high photovoltaic performance, adopting polymers with high molecular weight as donors is an ordinary strategy. However, the high molecular weight need to subtly control the reaction time and state, inevitably caused batch‐to‐batch variations. Herein, a strategy of steric effect is applied to benzodifuran (BDF)‐based polymer by introducing different positions of Cl atom, producing two polymers PBDFCl‐1 and PBDFCl‐2. The more twisted side chains conformation not only achieve the control of moderate molecular weight for PBDFCl‐2, but also easily form molecular stacking through adopting BDF unit and maintain sufficient polymeric crystallinity. Due to the optimized stacking mode and good blend miscibility, PBDFCl‐2‐based device exhibitsa more elegant power conversion efficiency (PCE) of 17.00% compared to PBDFCl‐1‐based device. This is the highest efficiency record for BDF‐based binary OSCs. Meanwhile, the PCE device variation of the different molecular weights for PBDFCl‐2 is little, indicating the reduction of the batch variation. Therefore, smartly using steric effect of Cl atom in strong crystalline BDF unit can form efficient molecular stacking regulations and realize the coordination of high‐performance and stable batch variance. [ABSTRACT FROM AUTHOR]

Superoxide dismutases (SODs) play critical roles in plants, especially in the maintenance of redox homeostasis. The response of SODs in Citrus (Citrus sinensis (L.) Osbeck) to citrus bacterial canker (CBC) infection were investigated. The CsSODs were identified, and their gene structures, phylogeny, conserved domains and motifs, predicted interactions, and chromosomal distribution were analyzed. CsSOD expression in response to stress-related plant hormones (salicylic acid, SA; methyl jasmonate, MeJA; and abscisic acid, ABA) and Xanthomonas citri subsp. citri (Xcc) infection were also investigated. Thirteen CsSODs were identified in C. sinensis, including four Fe/MnSODs and nine Cu/ZnSODs with typical functional domains. The CsSODs were distributed on chromosomes 3, 5, 7, and 8. Specific hormone-response motifs were identified in the gene promoter regions. Ten genes were induced by MeJA treatment, as shown by qRT-PCR, and were upregulated in the CBC-susceptible Wanjincheng citrus variety, while CsSOD06 and CsSOD08 were upregulated by ABA in both the Wanjincheng and the CBC-resistant Kumquat varieties. Xcc infection significantly altered the levels of most CsSODs. The overexpression of CsSOD06 and CsSOD08 resulted in increased hydrogen peroxide levels and SOD activity. Our findings highlight the significance of SOD enzymes in the plant response to pathogen infection and have a potential application for breeding CBC-tolerant citrus varieties. [ABSTRACT FROM AUTHOR]

This work reports the separation performance of a new π-conjugated copolymer (PBDB-T) with alternating electron-donor and electron-acceptor units as the stationary phase for capillary gas chromatography (GC). To date, they have not been explored in the field of chromatography. The PBDB-T column exhibited a column efficiency of 3850 plates m−1 determined by n-dodecane at 120 °C and high-resolution performance toward a wide range of aromatic isomers, particularly halobenzenes, phenols, anthracene and phenanthrene. Moreover, it showed excellent separation repeatability and reproducibility in terms of run-to-run, day-to-day and column-to-column and good thermal stability. This work demonstrates the good potential of the indicated D–A copolymer as a new class of stationary phase for chromatographic analyses. [ABSTRACT FROM AUTHOR]