Genome-wide identification and expression analysis of the bZIP transcription factors, and functional analysis in response to drought and cold stresses in pear (Pyrus breschneideri)

Molecular mechanism of abscisic acid signaling response factor VcbZIP55 to promote anthocyanin biosynthesis in blueberry (Vaccinium corymbosum)

A high content of anthocyanin in blueberry (Vaccinium corymbosum) is an important indicator to evaluate fruit quality. Abscisic acid (ABA) can promote anthocyanin biosynthesis, but since the molecular mechanism is unclear, clarifying the mechanism will improve for blueberry breeding and cultivation regulation. VcbZIP55 regulating anthocyanin synthesis in blueberry were screened and mined using the published Isoform-sequencing, RNA-Seq and qRT-PCR at different fruit developmental stages. Blueberry genetic transformation and transgenic experiments confirmed that VcbZIP55 could promote anthocyanin biosynthesis in blueberry adventitious buds, tobacco leaves, blueberry leaves and blueberry fruit. VcbZIP55 responded to ABA signals and its expression was upregulated in blueberry fruit. In addition, using VcbZIP55 for Yeast one hybrid assay (Y1H) and transient expression in tobacco leaves demonstrated an interaction between VcbZIP55 and a G-Box motif on the VcMYB1 promoter to activate the expression of VcMYB1. This study will lay the theoretical foundation for the molecular mechanisms of phytohormone regulation responsible for anthocyanin synthesis and provide theoretical support for blueberry quality improvement.

In-Depth Characterization of bZIP Genes in the Context of Endoplasmic Reticulum (ER) Stress in Brassica campestris ssp. chinensis

Numerous studies have been conducted to investigate the genomic characterization of bZIP genes and their involvement in the cellular response to endoplasmic reticulum (ER) stress. These studies have provided valuable insights into the coordinated cellular response to ER stress, which is mediated by bZIP transcription factors (TFs). However, a comprehensive and systematic investigations regarding the role of bZIP genes and their involvement in ER stress response in pak choi is currently lacking in the existing literature. To address this knowledge gap, the current study was initiated to elucidate the genomic characteristics of bZIP genes, gain insight into their expression patterns during ER stress in pak choi, and investigate the protein-to-protein interaction of bZIP genes with the ER chaperone BiP. In total, 112 members of the BcbZIP genes were identified through a comprehensive genome-wide analysis. Based on an analysis of sequence similarity, gene structure, conserved domains, and responsive motifs, the identified BcbZIP genes were categorized into 10 distinct subfamilies through phylogenetic analysis. Chromosomal location and duplication events provided insight into their genomic context and evolutionary history. Divergence analysis estimated their evolutionary history with a predicted divergence time ranging from 0.73 to 80.71 million years ago (MYA). Promoter regions of the BcbZIP genes were discovered to exhibit a wide variety of cis-elements, including light, hormone, and stress-responsive elements. GO enrichment analysis further confirmed their roles in the ER unfolded protein response (UPR), while co-expression network analysis showed a strong relationship of BcbZIP genes with ER-stress-responsive genes. Moreover, gene expression profiles and protein-protein interaction with ER chaperone BiP further confirmed their roles and capacity to respond to ER stress in pak choi.

PbrWRKY62-PbrADC1 module involves in superficial scald development of Pyrus bretschneideri Rehd.fruit via regulating putrescine biosynthesis

Putrescine plays a role in superficial scald development during the cold storage of pear fruit. However, the molecular mechanism behind this phenomenon has not been un-fully clarified until recently. In this study, a conjoint analysis of metabolites and gene expression profiles in the putrescine-metabolic pathway of P. bretschneideri Rehd. fruit followed by experimental validation revealed that PbrADC1, forming a homodimer in the chloroplast, was involved in putrescine biosynthesis and thus fruit chilling resistance. Additionally, the substrate-binding residue Cys546 in PbrADC1, whose activity was modified by H2O2, played a crucial role in arginine decarboxylation into agmatine. Through a combined analysis of the distribution of cis-acting elements in the PbrADC1 promoter as well as the expression profiles of related transcription factors (TFs), several TFs were identified as upstream regulators of PbrADC1 gene. Further investigation revealed that the nuclear PbrWRKY62 could directly bind to the W-box elements in the PbrADC1 promoter, activate its expression, enhance putrescine accumulation, and thus increase fruit chilling tolerance. In conclusion, our results suggest that the PbrWRKY62-PbrADC1 module is involved in the development of superficial scald in P. bretschneideri Rehd. fruit via regulating putrescine biosynthesis. Consequently, these findings could serve as valuable genetic resources for breeding scald-resistant pear fruit.

bZIP transcription factor PubZIP914 enhances production of fatty acid-derived volatiles in pear

'Nanguo' pear emitted a rich aroma when entirely ripe. The six-carbon (C6) volatiles, including the aldehydes, 2-hexenal, and hexanal, as well as their corresponding alcohols and esters which are derived from lipoxygenase pathway are the important volatile components in 'Nanguo' pears. However, the transcriptional regulation mechanism of aroma synthesis of 'Nanguo' pears remains largely unknown. bZIP transcription factors (TFs) mediate different developmental processes in plants. In this study, we identified and characterized a bZIP TF that is highly expressed and induced in 'Nanguo' pear fruits at the mature stage. The content of fatty acid-derived volatiles increased significantly in transgenic pears and tomatoes of PubZIP914 overexpression. Meanwhile, PubZIP914 could regulate PuLOX3.1 by binding directly to PuLOX3.1 promoter. The results of this study provide evidence demonstrating how bZIP transcription factors regulate fatty acid-derived volatiles biosynthesis during pear fruit ripening.

Brassinosteroid Signaling Pathways: Insights into Plant Responses under Abiotic Stress

With the growing global population, abiotic factors have emerged as a formidable threat to agricultural food production. If left unaddressed, these stress factors might reduce food yields by up to 25% by 2050. Plants utilize natural mechanisms, such as reactive oxygen species scavenging, to mitigate the adverse impacts of abiotic stressors. Diverse plants exhibit unique adaptations to abiotic stresses, which are regulated by phytohormones at various levels. Brassinosteroids (BRs) play a crucial role in controlling essential physiological processes in plants, including seed germination, xylem differentiation, and reproduction. The BR cascade serves as the mechanism through which plants respond to environmental stimuli, including drought and extreme temperatures. Despite two decades of research, the complex signaling of BRs under different stress conditions is still being elucidated. Manipulating BR signaling, biosynthesis, or perception holds promise for enhancing crop resilience. This review explores the role of BRs in signaling cascades and summarizes their substantial contribution to plants' ability to withstand abiotic stresses.

Genome-wide identification of bZIP gene family and expression analysis of BhbZIP58 under heat stress in wax gourd

BACKGROUND

The basic leucine zipper (bZIP) transcription factor family is one of the most abundant and evolutionarily conserved gene families in plants. It assumes crucial functions in the life cycle of plants, including pathogen defense, secondary metabolism, stress response, seed maturation, and flower development. Although the genome of wax gourd has been published, little is known about the functions, evolutionary background, and gene expression patterns of the bZIP gene family, which limits its utilization.

RESULTS

A total of 61 bZIP genes (BhbZIPs) were identified from wax gourd (Benincasa hispida) genome and divided into 12 subgroups. Whole-genome duplication (WGD) and dispersed duplication (DSD) were the main driving forces of bZIP gene family expansion in wax gourd, and this family may have undergone intense purifying selection pressure during the evolutionary process. We selected BhbZIP58, only one in the member of subgroup B, to study its expression patterns under different stresses, including heat, salt, drought, cold stress, and ABA treatment. Surprisingly, BhbZIP58 had a dramatic response under heat stress. BhbZIP58 showed the highest expression level in the root compared with leaves, stem, stamen, pistil, and ovary. In addition, BhbZIP58 protein was located in the nucleus and had transcriptional activation activity. Overexpression of BhbZIP58 in Arabidopsis enhanced their heat tolerance.

CONCLUSIONS

In this study, bZIP gene family is systematically bioinformatically in wax gourd for the first time. Particularly, BhbZIP58 may have an important role in heat stress. It will facilitate further research on the bZIP gene family regarding their evolutionary history and biological functions.

Transcription factor PbbZIP4 is targeted for proteasome-mediated degradation by the ubiquitin ligase PbATL18 to influence pear's resistance to Colletotrichum fructicola by regulating the expression of PbNPR3

Pear anthracnose caused by Colletotrichum fructicola is one of the main fungal diseases in all pear-producing areas. The degradation of ubiquitinated proteins by the 26S proteasome is a regulatory mechanism of eukaryotes. E3 ubiquitin ligase is substrate specific and is one of the most diversified and abundant enzymes in the regulation mechanism of plant ubiquitination. Although numerous studies in other plants have shown that the degradation of ubiquitinated proteins by the 26S proteasome is closely related to plant immunity, there are limited studies on them in pear trees. Here, we found that an E3 ubiquitin ligase, PbATL18, interacts with and ubiquitinates the transcription factor PbbZIP4, and this process is enhanced by C. fructicola infection. PbATL18 overexpression in pear callus enhanced resistance to C. fructicola infection, whereas PbbZIP4 overexpression increased sensitivity to C. fructicola infection. Silencing PbATL18 and PbbZIP4 in Pyrus betulaefolia seedlings resulted in opposite effects, with PbbZIP4 silencing enhancing resistance to C. fructicola infection and PbATL18 silencing increasing sensitivity to C. fructicola infection. Using yeast one-hybrid screens, an electrophoretic mobility shift assay, and dual-luciferase assays, we demonstrated that the transcription factor PbbZIP4 upregulated the expression of PbNPR3 by directly binding to its promoter. PbNPR3 is one of the key genes in the salicylic acid (SA) signal transduction pathway that can inhibit SA signal transduction. Here, we proposed a PbATL18-PbbZIP4-PbNPR3-SA model for plant response to C. fructicola infection. PbbZIP4 was ubiquitinated by PbATL18 and degraded by the 26S proteasome, which decreased the expression of PbNPR3 and promoted SA signal transduction, thereby enhancing plant C. fructicola resistance. Our study provides new insights into the molecular mechanism of pear response to C. fructicola infection, which can serve as a theoretical basis for breeding superior disease-resistant pear varieties.

Acetylation of inorganic pyrophosphatase by S-RNase signaling induces pollen tube tip swelling by repressing pectin methylesterase

Self-incompatibility (SI) is a widespread genetically determined system in flowering plants that prevents self-fertilization to promote gene flow and limit inbreeding. S-RNase-based SI is characterized by the arrest of pollen tube growth through the pistil. Arrested pollen tubes show disrupted polarized growth and swollen tips, but the underlying molecular mechanism is largely unknown. Here, we demonstrate that the swelling at the tips of incompatible pollen tubes in pear (Pyrus bretschneideri [Pbr]) is mediated by the SI-induced acetylation of the soluble inorganic pyrophosphatase (PPA) PbrPPA5. Acetylation at Lys-42 of PbrPPA5 by the acetyltransferase GCN5-related N-acetyltransferase 1 (GNAT1) drives accumulation of PbrPPA5 in the nucleus, where it binds to the transcription factor PbrbZIP77, forming a transcriptional repression complex that inhibits the expression of the pectin methylesterase (PME) gene PbrPME44. The function of PbrPPA5 as a transcriptional repressor does not require its PPA activity. Downregulating PbrPME44 resulted in increased levels of methyl-esterified pectins in growing pollen tubes, leading to swelling at their tips. These observations suggest a mechanism for PbrPPA5-driven swelling at the tips of pollen tubes during the SI response. The targets of PbrPPA5 include genes encoding cell wall-modifying enzymes, which are essential for building a continuous sustainable mechanical structure for pollen tube growth.

Systematic evolution of bZIP transcription factors in Malvales and functional exploration of AsbZIP14 and AsbZIP41 in Aquilaria sinensis

Introduction

Agarwood, the dark-brown resin produced by Aquilaria trees, has been widely used as incense, spice, perfume or traditional medicine and 2-(2-phenethyl) chromones (PECs) are the key markers responsible for agarwood formation. But the biosynthesis and regulatory mechanism of PECs were still not illuminated. The transcription factor of basic leucine zipper (bZIP) presented the pivotal regulatory roles in various secondary metabolites biosynthesis in plants, which might also contribute to regulate PECs biosynthesis. However, molecular evolution and function of bZIP are rarely reported in Malvales plants, especially in Aquilaria trees.

Methods and results

Here, 1,150 bZIPs were comprehensively identified from twelve Malvales and model species genomes and the evolutionary process were subsequently analyzed. Duplication types and collinearity indicated that bZIP is an ancient or conserved TF family and recent whole genome duplication drove its evolution. Interesting is that fewer bZIPs in A. sinensis than that species also experienced two genome duplication events in Malvales. 62 AsbZIPs were divided into 13 subfamilies and gene structures, conservative domains, motifs, cis-elements, and nearby genes of AsbZIPs were further characterized. Seven AsbZIPs in subfamily D were significantly regulated by ethylene and agarwood inducer. As the typical representation of subfamily D, AsbZIP14 and AsbZIP41 were localized in nuclear and potentially regulated PECs biosynthesis by activating or suppressing type III polyketide synthases (PKSs) genes expression via interaction with the AsPKS promoters.

Discussion

Our results provide a basis for molecular evolution of bZIP gene family in Malvales and facilitate the understanding the potential functions of AsbZIP in regulating 2-(2-phenethyl) chromone biosynthesis and agarwood formation.

From plant survival to thriving: exploring the miracle of brassinosteroids for boosting abiotic stress resilience in horticultural crops

Abiotic stresses pose significant threat to horticultural crop production worldwide. These stresses adversely affect plant growth, development, and ultimately declined crop growth, yield and quality. In recent years, plant scientists have been actively investigating innovative strategies to enhance abiotic stress resilience in crops, and one promising avenue of research focuses on the use of brassinosteroids (BRs). BRs are a class of plant hormones that play crucial roles in various physiological processes, including cell elongation, differentiation, and stress responses. They have emerged as potent regulators of plant growth and development, and their role in improving abiotic stress tolerance is gaining considerable attention. BRs have been shown to mitigate the negative effects of abiotic stresses by modulating key physiological and biochemical processes, including stomatal regulation, antioxidant defense, osmotic adjustment, and nutrient uptake. Abiotic stresses disrupt numerous physiological functions and lead to undesirable phenotypic traits in plants. The use of BRs as a tool to improve crop resilience offers significant promise for sustainable agriculture in the face of increasing abiotic stresses caused by climate change. By unraveling the phenomenon of BRs, this review emphasizes the potential of BRs as an innovative approach for boosting abiotic stress tolerance and improving the overall productivity and quality of horticultural crops. Further research and field trials are necessary to fully harness the benefits of BRs and translate these findings into practical applications for crop production systems.

Dissecting the features of TGA gene family in Saccharum and the functions of ScTGA1 under biotic stresses

Sugarcane is an important sugar and energy crop and smut disease caused by Sporisorium scitamineum is a major fungal disease which can seriously reduce the yield and quality of sugarcane. In plants, TGACG motif binding (TGA) transcription factors are involved in the regulation of salicylic acid (SA) and methyl jasmonate (MeJA) signaling pathways, as well as in response to various biotic and abiotic stresses. However, no TGA-related transcription factor has been reported in Saccharum. In the present study, 44 SsTGA genes were identified from Saccharum spontaneum, and were assorted into three clades (I, II, III). Cis-regulatory elements (CREs) analysis revealed that SsTGA genes may be involved in hormone and stress response. RNA-seq data and RT-qPCR analysis indicated that SsTGAs were constitutively expressed in different tissues and induced by S. scitamineum stress. In addition, a ScTGA1 gene (GenBank accession number ON416997) was cloned from the sugarcane cultivar ROC22, which was homologous to SsTGA1e in S. spontaneum and encoded a nucleus protein. It was constitutively expressed in sugarcane tissues and up-regulated by SA, MeJA and S. scitamineum stresses. Furthermore, transient overexpression of ScTGA1 in Nicotiana benthamiana could enhance its resistance to the infection of Ralstonia solanacearum and Fusarium solani var. coeruleum, by regulating the expression of immune genes related to hypersensitive response (HR), ethylene (ET), SA and jasmonic acid (JA) pathways. This study should contribute to our understanding on the evolution and function of the SsTGA gene family in Saccharum, and provide a basis for the functional identification of ScTGA1 under biotic stresses.

Genome-wide identification and characterization of the bZIP gene family and their function in starch accumulation in Chinese chestnut (Castanea mollissima Blume)

The transcription factors of basic leucine zipper (bZIP) family genes play significant roles in stress response as well as growth and development in plants. However, little is known about the bZIP gene family in Chinese chestnut (Castanea mollissima Blume). To better understand the characteristics of bZIPs in chestnut and their function in starch accumulation, a series of analyses were performed including phylogenetic, synteny, co-expression and yeast one-hybrid analyses. Totally, we identified 59 bZIP genes that were unevenly distributed in the chestnut genome and named them CmbZIP01 to CmbZIP59. These CmbZIPs were clustered into 13 clades with clade-specific motifs and structures. A synteny analysis revealed that segmental duplication was the major driving force of expansion of the CmbZIP gene family. A total of 41 CmbZIP genes had syntenic relationships with four other species. The results from the co-expression analyses indicated that seven CmbZIPs in three key modules may be important in regulating starch accumulation in chestnut seeds. Yeast one-hybrid assays showed that transcription factors CmbZIP13 and CmbZIP35 might participate in starch accumulation in the chestnut seed by binding to the promoters of CmISA2 and CmSBE1_2, respectively. Our study provided basic information on CmbZIP genes, which can be utilized in future functional analysis and breeding studies.

Brassinosteroid Supplementation Alleviates Chromium Toxicity in Soybean (Glycine max L.) via Reducing Its Translocation

Chromium (Cr) phytotoxicity severely inhibits plant growth and development which makes it a prerequisite to developing techniques that prevent Cr accumulation in food chains. However, little is explored related to the protective role of brassinosteroids (BRs) against Cr-induced stress in soybean plants. Herein, the morpho-physiological, biochemical, and molecular responses of soybean cultivars with/without foliar application of BRs under Cr toxicity were intensely investigated. Our outcomes deliberated that BRs application noticeably reduced Cr-induced phytotoxicity by lowering Cr uptake (37.7/43.63%), accumulation (63.92/81.73%), and translocation (26.23/38.14%) in XD-18/HD-19, plant tissues, respectively; besides, improved seed germination ratio, photosynthetic attributes, plant growth, and biomass, as well as prevented nutrient uptake inhibition under Cr stress, especially in HD-19 cultivar. Furthermore, BRs stimulated antioxidative defense systems, both enzymatic and non-enzymatic, the compartmentalization of ion chelation, diminished extra production of reactive oxygen species (ROS), and electrolyte leakage in response to Cr-induced toxicity, specifically in HD-19. In addition, BRs improved Cr stress tolerance in soybean seedlings by regulating the expression of stress-related genes involved in Cr accumulation, and translocation. Inclusively, by considering the above-mentioned biomarkers, foliar spray of BRs might be considered an effective inhibitor of Cr-induced damages in soybean cultivars, even in Cr polluted soil.

Application of exogenous glutathione decreases chromium translocation and alleviates its toxicity in soybean (Glycine max L.)

Chromium is considered one of the most severe toxic elements affecting agriculture. Soybean seedlings under chromium stress were treated with glutathione and buthionine sulfoximine. The effects of exogenous glutathione on the physiological effects of two different chromium-resistant soybean seedlings and the expression levels of expression levels related genes were studied. This study tested the seedling weight and SPAD values, detected enzymatic antioxidants (i.e., superoxide dismutase, peroxidase, catalase, catalase, ascorbate peroxidase), and non-enzymatic antioxidants (i.e., glutathione, proline, soluble sugars, and soluble phenols) that attenuate chromium-induced reactive oxygen species, and quantified several genes associated with glutathione-mediated chromium stress. The results showed that exogenous glutathione could improve the physiological adaptability of soybean seedlings by regulating photosynthesis, antioxidant, and related enzyme activities, osmotic system, the compartmentalization of ion chelation, and regulating the transcription level of related genes, thereby increasing the chromium accumulation of soybean seedlings, enhancing the tolerance of chromium stress, and reducing the toxicity of chromium. Overall, the application of glutathione alleviates chromium toxicity in soybeans, and this strategy may be a potential farming option for soybean bioremediation in chromium-contaminated soils.

Genome-Wide Identification and Analysis of bZIP Gene Family and Resistance of TaABI5 (TabZIP96) under Freezing Stress in Wheat (Triticum aestivum)

The basic leucine zipper (bZIP) regulates plant growth and responds to stress as a key transcription factor of the Abscisic acid (ABA) signaling pathway. In this study, TabZIP genes were identified in wheat and the gene structure, physicochemical properties, cis-acting elements, and gene collinearity were analyzed. RNA-Seq and qRT-PCR analysis showed that ABA and abiotic stress induced most TabZIP genes expression. The ectopic expression of TaABI5 up-regulated the expression of several cold-responsive genes in Arabidopsis. Physiological indexes of seedlings of different lines under freezing stress showed that TaABI5 enhanced the freezing tolerance of plants. Subcellular localization showed that TaABI5 is localized in the nucleus. Furthermore, TaABI5 physically interacted with cold-resistant transcription factor TaICE1 in yeast two-hybrid system. In conclusion, this study identified and analyzed members of the TabZIP gene family in wheat. It proved for the first time that the gene TaABI5 affected the cold tolerance of transgenic plants and was convenient for us to understand the cold resistance molecular mechanism of TaABI5. These results will provide a new inspiration for further study on improving plant abiotic stress resistance.

The bZIP transcription factors in Liriodendron chinense: Genome-wide recognition, characteristics and cold stress response

The basic leucine zipper (bZIP) is a transcription factor family that plays critical roles in abiotic and biotic stress responses as well as plant development and growth. A comprehensive genome-wide study in Liriodendron chinense was conducted to identify 45 bZIP transcription factors (LchibZIPs), which were divided into 13 subgroups according the phylogenetic analysis. Proteins in the same subgroup shared similar gene structures and conserved domains, and a total of 20 conserved motifs were revealed in LchibZIP proteins. Gene localization analysis revealed that LchibZIP genes were unequally distributed across 16 chromosomes, and that 4 pairs of tandem and 9 segmental gene duplications existed. Concluding that segmental duplication events may be strongly associated with the amplification of the L. chinense bZIP gene family. We also assessed the collinearity of LchibZIPs between the Arabidopsis and Oryza and showed that the LchibZIP is evolutionarily closer to O. sativa as compared to the A. thaliana. The cis-regulatory element analysis showed that LchibZIPs clustered in one subfamily are involved in several functions. In addition, we gathered novel research suggestions for further exploration of the new roles of LchibZIPs from protein-protein interactions and gene ontology annotations of the LchibZIP proteins. Using the RNA-seq data and qRT-PCR we analyzed the gene expression patterns of LchibZIP genes, and showed that LchibZIP genes regulate cold stress, especially LchibZIP4 and LchibZIP7; and LchibZIP2 and LchibZIP28 which were up-regulated and down-regulated by cold stress, respectively. Studies of genetic engineering and gene function in L. chinense can benefit greatly from the thorough investigation and characterization of the L. chinense bZIP gene family.