BTB Protein Research Articles

Function of ZmBT2a gene in resistance to pathogen infection in maize

The BTB-TAZ protein is a subfamily of the BTB protein family and plays a crucial regulatory role in plant resistance to pathogen infection. However, the function of the maize BTB-TAZ protein ZmBT2a in maize resistance to pathogens has not been reported. Here, we investigate the role of ZmBT2a in maize resistance to pathogen infection by examining its expression characteristics. The results showed that the expression level of ZmBT2a changed significantly in response to biotic and abiotic stresses in maize. Moreover, ZmBT2a-OE exhibited enhanced resistance to Botrytis cinerea and Pseudomonas syringae pv. tomato DC3000, while the maize ZmBT2a mutants Zmbt2a-1 and Zmbt2a-2 showed increased sensitivity to Fusarium graminearum and Cochliobolus carbonum infections. Notably, the expression of the key synthetic genes ZmLOXs and pathogenesis-related genes ZmPRs in the JA synthesis pathway was significantly down-regulated during F. graminearum infection. Additionally, yeast two-hybrid assays confirmed the direct interaction between ZmBT2a and E3 ubiquitinated proteins ZmCUL3a and ZmCUL3b. These findings suggest that the ZmBT2a gene is crucial in maize resistance to pathogen infection. It is hypothesized that ZmBT2a binds to ZmCUL3 and, through ubiquitination, affects the transcriptional regulation of ZmLOXs and ZmPRs by downstream transcription factors, thus participating in the disease resistance process of maize.

Identification and Expression Analysis of the BTB/POZ Gene Family in Solanum tuberosum

The BTB/POZ (broad-complex, tramtrack, and bric-a-brac) family of proteins is widespread in plants and animals and plays important roles in growth, development, metabolism, and environmental responses. There are few reports on BTB family genes in potato. In this study, 34 sequences containing conserved BTB domains were obtained from the potato gene database, and the phylogenetic, physical, and chemical properties, gene structure, conserved motif, domain, and chromosomal localization of the potato BTB protein family were analyzed via bioinformatics methods. In addition, we used qRT-PCR to detect 12 selected StBTB genes. The results confirmed that these genes are involved in cold, ABA, salt, hydrogen peroxide (H2O2), drought, and low-nitrogen stress, which is highly important for elucidating BTB family members and studying stress response and tolerance mechanisms. This study provides a theoretical basis for the study of the function and expression of potato BTB and lays a solid foundation for further understanding the molecular mechanism of the potato BTB gene under various environmental stresses.

MdbHLH160 is stabilized via reduced MdBT2-mediated degradation to promote MdSOD1 and MdDREB2A-like expression for apple drought tolerance.

Drought stress is a key environmental factor limiting the productivity, quality, and geographic distribution of crops worldwide. Abscisic acid (ABA) plays an important role in plant drought stress responses, but the molecular mechanisms remain unclear. Here, we report an ABA-responsive bHLH transcription factor, MdbHLH160, which promotes drought tolerance in Arabidopsis (Arabidopsis thaliana) and apple (Malus domestica). Under drought conditions, MdbHLH160 is directly bound to the MdSOD1 (superoxide dismutase 1) promoter and activated its transcription, thereby triggering reactive oxygen species (ROS) scavenging and enhancing apple drought tolerance. MdbHLH160 also promoted MdSOD1 enzyme activity and accumulation in the nucleus through direct protein interactions, thus inhibiting excessive nuclear ROS levels. Moreover, MdbHLH160 directly upregulated the expression of MdDREB2A-like, a DREB (dehydration-responsive element binding factor) family gene that promotes apple drought tolerance. Protein degradation and ubiquitination assays showed that drought and ABA treatment stabilized MdbHLH160. The BTB protein MdBT2 was identified as an MdbHLH160-interacting protein that promoted MdbHLH160 ubiquitination and degradation, and ABA treatment substantially inhibited this process. Overall, our findings provide insights into the molecular mechanisms of ABA-modulated drought tolerance at both the transcriptional and post-translational levels via the ABA-MdBT2-MdbHLH160-MdSOD1/MdDREB2A-like cascade.

BTB protein family and human breast cancer: signaling pathways and clinical progress.

Breast cancer is considered the number one killer of women both in China and abroad, and the leading cause of cancer death. It severely affects female health-related quality of life. Broad-complex, tramtrack, bric à brac (BTB) protein family was first discovered in drosophila as early as in 1993 by Godt D and peers, since then, more family members and their critical biological functions were uncovered. Moreover, researchers around the world have recently demonstrated that numerous signaling pathways connect BTB family members and human breast cancer. In this review, we critically discuss these findings regarding the essential mechanisms and functions of the BTB protein family in mediating the organic processes of human breast cancer. Meanwhile, we summarize the signaling pathways the BTB protein family participates in. And we address that BTB proteins regulate the growth, apoptosis, and other behaviors of breast cancer cells. We also point out the future directions for further studies in this field. The relevant onlineliteratures have been reviewed for this article. This review could offer an update on novel molecular targets for treating human breast cancer and new insights into BTB protein family research.

OsBBX19-OsBTB97/OsBBX11 module regulates spikelet development and yield production in rice

Spikelet and floral-related organs are important agronomic traits for rice grain yield. BTB (broad-complex, tram track, and bric-abrac) proteins control various developmental functions in plants; however, the molecular mechanism of BTB proteins underlying grain development and yield production is still unknown. Here, we evaluated the molecular mechanism of a previously unrecognized functional gene, namely OsBTB97 that regulates the floral and spikelet-related organs which greatly affect the final grain yield. We found that the knockdown of the OsBTB97 gene had significant impacts on the development of spikelet-related organs and grain size, resulting in a decrease in yield, by altering the transcript levels of various spikelet- and grain-related genes. Furthermore, we found that the knockout mutants of two BBX genes, OsBBX11 and OsBBX19, which interact with the OsBTB97 protein at translation and transcriptional level, respectively, displayed lower OsBTB97 expression, suggesting the genetic relationship between the BTB protein and the BBX transcription factors in rice. Taken together, our study dissects the function of the novel OsBTB97 by interacting with two BBX proteins and an OsBBX19-OsBTB97/OsBBX11 module might function in the spikelet development and seed production in rice. The outcome of the present study provides promising knowledge about BTB proteins in the improvement of crop production in plants.

Towards Reverse Vaccinology for Bovine TB: High Throughput Expression of Full Length Recombinant Mycobacterium bovis Proteins.

Bovine tuberculosis caused by Mycobacterium bovis, is a significant global pathogen causing economic loss in livestock and zoonotic TB in man. Several vaccine approaches are in development including reverse vaccinology which uses an unbiased approach to select open reading frames (ORF) of potential vaccine candidates, produce them as recombinant proteins and assesses their immunogenicity by direct immunization. To provide feasibility data for this approach we have cloned and expressed 123 ORFs from the M. bovis genome, using a mixture of E. coli and insect cell expression. We used a concatenated open reading frames design to reduce the number of clones required and single chain fusion proteins for protein pairs known to interact, such as the members of the PPE-PE family. Over 60% of clones showed soluble expression in one or the other host and most allowed rapid purification of the tagged bTB protein from the host cell background. The catalogue of recombinant proteins represents a resource that may be suitable for test immunisations in the development of an effective bTB vaccine.

BTB and TAZ domain protein BT4 positively regulates the resistance to Botrytis cinerea in Arabidopsis

ABSTRACT BT4 gene was identified to play an important role in Arabidopsis resistance to pst DC3000 in preliminary studies. However, the specific function and molecular mechanism of BT4 gene in regulation of Arabidopsis resistance to Botrytis cinerea had not been described to date. In this study, we found that the expression of BT4 was induced by wounding and B. cinerea inoculation in Arabidopsis. After inoculated with B. cinerea, T-DNA insertion mutants of the BT4 gene, bt4, showed significant susceptibility symptoms, whereas no significant symptoms were found in wild-type (WT), the complemented transgenic plants (CE), and the overexpression transgenic plants (OE). After inoculated with B. cinerea, the expression levels of JAR1 and PDF1.2 genes in bt4 mutant were induced; however, the expression levels of these genes in bt4 mutant were significantly lower than those in the WT, CE, and OE. These results indicated that the BT4 positively regulate the expression of genes in JA/ET signaling pathways. Therefore, the BT4 may be involved in the regulation of JA/ET signaling pathways to affect Arabidopsis resistance to B. cinerea.

The apple BTB protein MdBT2 positively regulates MdCOP1 abundance to repress anthocyanin biosynthesis.

The ubiquitin ligase CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) plays a central role in light-induced anthocyanin biosynthesis. However, the upstream regulatory factors of COP1 remain poorly understood, particularly in horticultural plants. Here, we identified an MdCOP1-interacting protein, BROAD-COMPLEX, TRAMTRACK AND BRIC A BRAC2 (MdBT2), in apple (Malus domestica). MdBT2 is a BTB protein that directly interacts with and stabilizes MdCOP1 by inhibiting self-ubiquitination. Fluorescence observation and cell fractionation assays showed that MdBT2 increased the abundance of MdCOP1 in the nucleus. Moreover, a series of phenotypic analyses indicated that MdBT2 promoted MdCOP1-mediated ubiquitination and degradation of the MdMYB1 transcription factor, inhibiting the expression of anthocyanin biosynthesis genes and anthocyanin accumulation. Overall, our findings reveal a molecular mechanism by which MdBT2 positively regulates MdCOP1, providing insight into MdCOP1-mediated anthocyanin biosynthesis.

BTB protein MdBT2 negatively regulates iron homeostasis by interacting with MdNAC1 in apple

NAC transcription factors play an important role in plant abiotic stress response. However, the molecular mechanism of how it regulates iron accumulation remain largely unknown in apple. Here, we show that MdNAC1 positively regulates iron accumulation under iron deficiency conditions. Overexpression of MdNAC1 show higher levels of iron accumulation and chlorophyll content as well as activated the activity of plasma membrane (PM) H + -ATPases in response to iron deficiency. Quantitative PCR (qPCR) analysis showed that the expression of several iron-related genes were significantly up-regulated in transgenic apple calli. Additionally, we identify an MdBT2 protein that interacts with the MdNAC1 protein. MdBT2 negatively regulates the protein stability of MdNAC1 by degrading it through the ubiquitinated 26S proteasome pathway. In addition, overexpression of MdBT2 in apple and Arabidopsis exhibited inhibition of iron accumulation and showed chlorosis in the new leaves. In sum, our study provided molecular and genetic evidence that the MdBT2 may negatively regulate iron response by mediating the MdNAC1 stability. • We identified an NAC transcription factor, MdNAC1, from apple and demonstrated that it was localized in the nucleus. • The over expression of MdNAC1 increased iron accumulation in transgenic apple calli and Arabidopsis. • MdBT2 interacts with MdNAC1and mediates the ubiquitination of MdNAC1.

The BTB protein MdBT2 recruits auxin signaling components to regulate adventitious root formation in apple.

Ubiquitination is an important post-translational protein modification. Although BROAD-COMPLEX, TRAMTRACK AND BRIC A BRAC and TRANSCRIPTION ADAPTOR PUTATIVE ZINC FINGER domain protein 2 (BT2) is involved in many biological processes, its role in apple (Malus domestic) root formation remains unclear. Here, we revealed that MdBT2 inhibits adventitious root (AR) formation through interacting with AUXIN RESPONSE FACTOR8 (MdARF8) and INDOLE-3-ACETIC ACID INDUCIBLE3 (MdIAA3). MdBT2 facilitated MdARF8 ubiquitination and degradation through the 26S proteasome pathway and negatively regulated GRETCHEN HAGEN 3.1 (MdGH3.1) and MdGH3.6 expression. MdARF8 regulates AR formation through inducing transcription of MdGH3s (MdGH3.1, MdGH3.2, MdGH3.5, and MdGH3.6). In addition, MdBT2 facilitated MdIAA3 stability and slightly promoted its interaction with MdARF8. MdIAA3 inhibited AR formation by forming heterodimers with MdARF8 as well as other MdARFs (MdARF5, MdARF6, MdARF7, and MdARF19). Our findings reveal that MdBT2 acts as a negative regulator of AR formation in apple.

Genome-Wide Identification and Expression Analysis of the BTB Domain-Containing Protein Gene Family in Sugar Beet

Cercospora leaf spots (CLSs) is a fungal disease of sugar beet caused by C. beticola, which damages leaves and leads to yield cut on sugar beet worldwide. BTB protein genes are critical to plant defense against bacterial infection. Here, 49 members of the BTB protein gene family were identified from the big data of the sugar beet genome, and bioinformatics was used to analyze the BTB protein family. Through molecular techniques, C. beticola of CLS was identified. In addition, the transcriptome data of sugar beet resistant and susceptible materials after C. beticola infection were obtained. Three BTB genes most significantly related to C. beticola stress were screened from the transcriptome data. The three genes are BvBTB1, BvBTB2, and BvBTB3, their full-length cDNA sequences were acquired by RT-PCR. The phenotypes of sugar beet resistant and susceptible materials under different spore concentrations of C. beticola were analyzed. Further, under the stress of C. beticola, qRT-PCR results showed that the expression levels of BvBTB1, BvBTB2, and BvBTB3 in roots and leaves were tissue-specific and expressed differently in various tissues. BvBTB1, BvBTB2, and BvBTB3 were overexpressed in the resistant and susceptible materials within five days after C. beticola infection: the peak appeared on the fifth day, and the highest expression was 25 times that of the control group. However, the lowest was 1.1 times of the control group, moreover, the expression in the resistant material was higher than that in the susceptible material. Overall, these results showed that BvBTB genes were involved in the response in sugar beet to C. beticola infection. Therefore, the study provided a scientific theoretical basis for developing new resistant varieties in sugar beet.

A combined application of molecular docking technology and indirect ELISA for the serodiagnosis of bovine tuberculosis.

BackgroundThere is an urgent need to find reliable and rapid bovine tuberculosis (bTB) diagnostics in response to the rising prevalence of bTB worldwide. Toll-like receptor 2 (TLR2) recognizes components of bTB and initiates antigen-presenting cells to mediate humoral immunity. Evaluating the affinity of antigens with TLR2 can form the basis of a new method for the diagnosis of bTB based on humoral immunity.ObjectivesTo develop a reliable and rapid strategy to improve diagnostic tools for bTB.MethodsIn this study, we expressed and purified the sixteen bTB-specific recombinant proteins in Escherichia coli. The two antigenic proteins, MPT70 and MPT83, which were most valuable for serological diagnosis of bTB were screened. Molecular docking technology was used to analyze the affinity of MPT70, MPT83, dominant epitope peptide of MPT70 (M1), and dominant epitope peptide MPT83 (M2) with TLR2, combined with the detection results of enzyme-linked immunosorbent assay to evaluate the molecular docking effect.ResultsThe results showed that interaction surface Cα-atom root mean square deviation of proteins (M1, M2, MPT70, MPT83)-TLR2 protein are less than 2.5 A, showing a high affinity. It is verified by clinical serum samples that MPT70, MPT83, MPT70-MPT83 showed good diagnostic potential for the detection of anti-bTB IgG and M1, M2 can replace the whole protein as the detection antigen.ConclusionsMolecular docking to evaluate the affinity of bTB protein and TLR2 combined with ELISA provides new insights for the diagnosis of bTB.

The Armadillo BTB Protein ABAP1 Is a Crucial Player in DNA Replication and Transcription of Nematode-Induced Galls.

The biogenesis of root-knot nematode (Meloidogyne spp.)-induced galls requires the hyperactivation of the cell cycle with controlled balance of mitotic and endocycle programs to keep its homeostasis. To better understand gall functioning and to develop new control strategies for this pest, it is essential to find out how the plant host cell cycle programs are responding and integrated during the nematode-induced gall formation. This work investigated the spatial localization of a number of gene transcripts involved in the pre-replication complex during DNA replication in galls and report their akin colocation with the cell cycle S-phase regulator Armadillo BTB Arabidopsis Protein 1 (ABAP1). ABAP1 is a negative regulator of pre-replication complex controlling DNA replication of genes involved in control of cell division and proliferation; therefore, its function has been investigated during gall ontogenesis. Functional analysis was performed upon ABAP1 knockdown and overexpression in Arabidopsis thaliana. We detected ABAP1 promoter activity and localized ABAP1 protein in galls during development, and its overexpression displayed significantly reduced gall sizes containing atypical giant cells. Profuse ABAP1 expression also impaired gall induction and hindered nematode reproduction. Remarkably, ABAP1 knockdown likewise negatively affected gall and nematode development, suggesting its involvement in the feeding site homeostasis. Microscopy analysis of cleared and nuclei-stained whole galls revealed that ABAP1 accumulation resulted in aberrant giant cells displaying interconnected nuclei filled with enlarged heterochromatic regions. Also, imbalanced ABAP1 expression caused changes in expression patterns of genes involved in the cell division control as demonstrated by qRT-PCR. CDT1a, CDT1b, CDKA;1, and CYCB1;1 mRNA levels were significantly increased in galls upon ABAP1 overexpression, possibly contributing to the structural changes in galls during nematode infection. Overall, data obtained in galls reinforced the role of ABAP1 controlling DNA replication and mitosis and, consequently, cell proliferation. ABAP1 expression might likely take part of a highly ordered mechanism balancing of cell cycle control to prevent gall expansion. ABAP1 expression might prevent galls to further expand, limiting excessive mitotic activity. Our data strongly suggest that ABAP1 as a unique plant gene is an essential component for cell cycle regulation throughout gall development during nematode infection and is required for feeding site homeostasis.

Human CTCF Interacts with Drosophila CP190, but not with Kaiso.

Human CTCF (hCTCF) is a major architectural protein in mammals. In Drosophila, the CTCF homologue (dCTCF) interacts with the BTB domain of the CP190 protein, which is involved in the establishment of open chromatin and activity of insulators. Previously, it was shown that the BTB protein Kaiso interacts with hCTCF and regulates its activity. We have carried out a detailed study of the interaction between these proteins in the yeast two-hybrid assay. Surprisingly, Kaiso did not interact with hCTCF and its Drosophila homologue. On the other hand, CP190 interacted with the C-terminus of hCTCF. The results obtained demonstrate that the interaction between CTCF and CP190 proteins is highly conserved. It is likely that humans have other BTB proteins that perform the functions described for the Drosophila CP190.

The apple 14-3-3 protein MdGRF11 interacts with the BTB protein MdBT2 to regulate nitrate deficiency-induced anthocyanin accumulation

Nitrogen is an important factor that affects plant anthocyanin accumulation. In apple, the nitrate-responsive BTB/TAZ protein MdBT2 negatively regulates anthocyanin biosynthesis. In this study, we found that MdBT2 undergoes posttranslational modifications in response to nitrate deficiency. Yeast two-hybrid, protein pull-down, and bimolecular fluorescence complementation (BiFC) assays showed that MdBT2 interacts with MdGRF11, a 14-3-3 protein; 14-3-3 proteins compose a family of highly conserved phosphopeptide-binding proteins involved in multiple physiological and biological processes. The interaction of MdGRF11 negatively regulated the stability of the MdBT2 protein via a 26S proteasome-dependent pathway, which increased the abundance of MdMYB1 proteins to activate the expression of anthocyanin biosynthesis-related genes. Taken together, the results demonstrate the critical role of 14-3-3 proteins in the regulation of nitrate deficiency-induced anthocyanin accumulation. Our results provide a novel avenue to elucidate the mechanism underlying the induction of anthocyanin biosynthesis in response to nitrate deficiency.

The regulatory module MdBT2-MdMYB88/MdMYB124-MdNRTs regulates nitrogen usage in apple.

Less than 40% of the nitrogen (N) fertilizer applied to soil is absorbed by crops. Thus, improving the N use efficiency of crops is critical for agricultural development. However, the underlying regulation of these processes remains largely unknown, particularly in woody plants. By conducting yeast two-hybrid assays, we identified one interacting protein of MdMYB88 and MdMYB124 in apple (Malus × domestica), namely BTB and TAZ domain protein 2 (MdBT2). Ubiquitination and protein stabilization analysis revealed that MdBT2 ubiquitinates and degrades MdMYB88 and MdMYB124 via the 26S proteasome pathway. MdBT2 negatively regulates nitrogen usage as revealed by the reduced fresh weight, dry weight, N concentration, and N usage index of MdBT2 overexpression calli under low-N conditions. In contrast, MdMYB88 and MdMYB124 increase nitrate absorption, allocation, and remobilization by regulating expression of MdNRT2.4, MdNRT1.8, MdNRT1.7, and MdNRT1.5 under N limitation, thereby regulating N usage. The results obtained illustrate the mechanism of a regulatory module comprising MdBT2-MdMYB88/MdMYB124-MdNRTs, through which plants modulate N usage. These data contribute to a molecular approach to improve the N usage of fruit crops under limited N acquisition.

Cullin 3 and Its Role in Tumorigenesis.

Cullin 3 (Cul3) family of ubiquitin ligases comprises three components, the RING finger protein RBX1, the Cul3 scaffold, and a Bric-a-brac/Tramtrack/Broad complex (BTB) protein. The BTB protein serves as a bridge to connect Cul3 to substrate and is functionally equivalent to the combination of substrate adaptor and linker in other Cullin complexes. Human genome encodes for ~180 BTB proteins, implying a broad spectrum of ubiquitination signals and substrate repertoire. Accordingly, Cul3 ubiquitin ligases are involved in diverse cellular processes, including cell division, differentiation, cytoskeleton remodeling, stress responses, and nerve cell functions. Emerging evidence has pointed to the prominent role of Cul3 ubiquitin ligases in cancer. This chapter will describe recent advances on the roles of Cul3 E3 ligase complexes in regulating various cancer hallmarks and therapeutic responses and the mutation/dysregulation of Cul3 substrate adaptors in cancer. In particular, we will focus on several extensively studied substrate adaptors, such as Keap1, SPOP, KLHL20, and LZTR1, and will also discuss other recently identified Cul3 adaptors with oncogenic or tumor-suppressive functions. We conclude that Cul3 ubiquitin ligases represent master regulators of human malignancies and highlight the importance of developing modulating agents for oncogenic/tumor-suppressive Cul3 E3 ligase complexes to prevent or intervene tumorigenesis.

AtSIBP1, a Novel BTB Domain-Containing Protein, Positively Regulates Salt Signaling in Arabidopsis thaliana.

Because they are sessile organisms, plants need rapid and finely tuned signaling pathways to adapt to adverse environments, including salt stress. In this study, we identified a gene named Arabidopsis thaliana stress-induced BTB protein 1 (AtSIBP1), which encodes a nucleus protein with a BTB domain in its C-terminal side and is induced by salt and other stresses. The expression of the β-glucuronidase (GUS) gene driven by the AtSIBP1 promoter was found to be significantly induced in the presence of NaCl. The sibp1 mutant that lost AtSIBP1 function was found to be highly sensitive to salt stress and more vulnerable to salt stress than the wild type WT, while the overexpression of AtSIBP1 transgenic plants exhibited more tolerance to salt stress. According to the DAB staining, the sibp1 mutant accumulated more reactive oxygen species (ROS) than the WT and AtSIBP1 overexpression plants after salt stress. In addition, the expression levels of stress-induced marker genes in AtSIBP1 overexpression plants were markedly higher than those in the WT and sibp1 mutant plants. Therefore, our results demonstrate that AtSIBP1 was a positive regulator in salinity responses in Arabidopsis.

Ethylene Response Factor ERF11 Activates BT4 Transcription to Regulate Immunity to Pseudomonas syringae.

Pseudomonas syringae, a major hemibiotrophic bacterial pathogen, causes many devastating plant diseases. However, the transcriptional regulation of plant defense responses to P. syringae remains largely unknown. Here, we found that gain-of-function of BTB AND TAZ DOMAIN PROTEIN 4 (BT4) enhanced the resistance of Arabidopsis (Arabidopsis thaliana) to Pst DC3000 (Pseudomonas syringae pv. tomato DC3000). Disruption of BT4 also weakened the salicylic acid (SA)-induced defense response to Pst DC3000 in bt4 mutants. Further investigation indicated that, under Pst infection, transcription of BT4 is modulated by components of both the SA and ethylene (ET) signaling pathways. Intriguingly, the specific binding elements of ETHYLENE RESPONSE FACTOR (ERF) proteins, including dehydration responsive/C-repeat elements and the GCC box, were found in the putative promoter of BT4 Based on publicly available microarray data and transcriptional confirmation, we determined that ERF11 is inducible by salicylic acid and Pst DC3000 and is modulated by the SA and ET signaling pathways. Consistent with the function of BT4, loss-of-function of ERF11 weakened Arabidopsis resistance to Pst DC3000 and the SA-induced defense response. Biochemical and molecular assays revealed that ERF11 binds specifically to the GCC box of the BT4 promoter to activate its transcription. Genetic studies further revealed that the BT4-regulated Arabidopsis defense response to Pst DC3000 functions directly downstream of ERF11. Our findings indicate that transcriptional activation of BT4 by ERF11 is a key step in SA/ET-regulated plant resistance against Pst DC3000, enhancing our understanding of plant defense responses to hemibiotrophic bacterial pathogens.

Apple bZIP transcription factor MdbZIP44 regulates abscisic acid-promoted anthocyanin accumulation.

Phytohormone abscisic acid (ABA) induces anthocyanin biosynthesis; however, the underlying molecular mechanism is less known. In this study, we found that the apple MYB transcription factor MdMYB1 activated anthocyanin biosynthesis in response to ABA. Using a yeast screening technique, we isolated MdbZIP44, an ABA-induced bZIP transcription factor in apple, as a co-partner with MdMYB1. MdbZIP44 promoted anthocyanin accumulation in response to ABA by enhancing the binding of MdMYB1 to the promoters of downstream target genes. Furthermore, we identified MdBT2, a BTB protein, as an MdbZIP44-interacting protein. A series of molecular, biochemical, and genetic analysis suggested that MdBT2 degraded MdbZIP44 protein through the Ubiquitin-26S proteasome system, thus inhibiting MdbZIP44-modulated anthocyanin biosynthesis. Taken together, we reveal a novel working mechanism of MdbZIP44-mediated anthocyanin biosynthesis in response to ABA.