The phylogeny of C/S1 bZIP transcription factors reveals a shared algal ancestry and the pre-angiosperm translational regulation of S1 transcripts

Genome-Wide Analysis of C/S1-bZIP Subfamilies in Populus tomentosa and Unraveling the Role of PtobZIP55/21 in Response to Low Energy

C/S1 basic leucine zipper (bZIP) transcription factors are essential for plant survival under energy deficiency. However, studies on the responses of C/S1-bZIPs to low energy in woody plants have not yet been reported. In this study, members of C/S1-bZIP subfamilies in Populus tomentosa were systematically analyzed using bioinformatic approaches. Four C-bZIPs and 10 S1-bZIPs were identified, and their protein properties, phylogenetic relationships, gene structures, conserved motifs, and uORFs were systematically investigated. In yeast two-hybrid assays, direct physical interactions between C-bZIP and S1-bZIP members were observed, highlighting their potential functional synergy. Moreover, expression profile analyses revealed that low energy induced transcription levels of most C/S1-bZIP members, with bZIP55 and bZIP21 (a homolog of bZIP55) exhibiting particularly significant upregulation. When the expression of bZIP55 and bZIP21 was co-suppressed using artificial microRNA mediated gene silencing in transgenic poplars, root growth was promoted. Further analyses revealed that bZIP55/21 negatively regulated the root development of P. tomentosa in response to low energy. These findings provide insights into the molecular mechanisms by which C/S1-bZIPs regulate poplar growth and development in response to energy deprivation.

Current perspectives on the regulatory mechanisms of sucrose accumulation in sugarcane

Sugars transported from leaves (source) to stems (sink) energize cell growth, elongation, and maintenance. which are regulated by a variety of genes. This review reflects progress and prospects in the regulatory mechanism for maximum sucrose accumulation, including the role of sucrose metabolizing enzymes, sugar transporters and the elucidation of post-transcriptional control of sucrose-induced regulation of translation (SIRT) in the accumulation of sucrose. The current review suggests that SIRT is emerging as a significant mechanism controlling Scbzip44 activities in response to endogenous sugar signals (via the negative feedback mechanism). Sucrose-controlled upstream open reading frame (SC-uORF) exists at the 5' leader region of Scbzip44's main ORF, which inhibits sucrose accumulation through post-transcriptional regulatory mechanisms. Sucrose transporters (SWEET1a/4a/4b/13c, TST, SUT1, SUT4 and SUT5) are crucial for sucrose translocation from source to sink. Particularly, SWEET13c was found to be a major contributor to the efflux in the transportation of stems. Tonoplast sugar transporters (TSTs), which import sucrose into the vacuole, suggest their tissue-specific role from source to sink. Sucrose cleavage has generally been linked with invertase isozymes, whereas sucrose synthase (SuSy)-catalyzed metabolism has been associated with biosynthetic processes such as UDP-Glc, cellulose, hemicellulose and other polymers. However, other two key sucrose-metabolizing enzymes, such as sucrose-6-phosphate phosphohydrolase (S6PP) and sucrose phosphate synthase (SPS) isoforms, have been linked with sucrose biosynthesis. These findings suggest that manipulation of genes, such as overexpression of SPS genes and sucrose transporter genes, silencing of the SC-uORF of Scbzip44 (removing the 5' leader region of the main ORF that is called SIRT-Insensitive) and downregulation of the invertase genes, may lead to maximum sucrose accumulation. This review provides an overview of sugarcane sucrose-regulating systems and baseline information for the development of cultivars with higher sucrose accumulation.

OsbZIP38/87-mediated activation of OsHXK7 improves the viability of rice cells under hypoxic conditions

Maintenance of energy metabolism is critical for rice (Oryza sativa) tolerance under submerged cultivation. Here, OsHXK7 was the most actively induced hexokinase gene in the embryos of hypoxically germinating rice seeds. Suspension-cultured cells established from seeds of T-DNA null mutants for the OsHXK7 locus did not regrow after 3-d-hypoxic stress and showed increased susceptibility to low-oxygen stress-in terms of viability-and decreased alcoholic fermentation activities compared to those of the wild-type. The promoter element containing the TGACG-motif, a well-known target site for the basic leucine zipper (bZIP) transcription factors, was responsible for sugar regulation of the OsHXK7 promoter activity. Systematic screening of the OsbZIP genes showing the similar expression patterns to that of OsHXK7 in the transcriptomic datasets produced two bZIP genes, OsbZIP38 and 87, belonging to the S1 bZIP subfamily as the candidate for the activator for this gene expression. Gain- and loss-of-function experiments through transient expression assays have demonstrated that these two bZIP proteins are indeed involved in the induction of OsHXK7 expression under starvation or low-energy conditions. Our finding suggests that C/S1 bZIP network-mediated hypoxic deregulation of sugar-responsive genes may work in concert for the molecular adaptation of rice cells to submergence.

Wheat bZIPC1 interacts with FT2 and contributes to the regulation of spikelet number per spike

KEY MESSAGE

The wheat transcription factor bZIPC1 interacts with FT2 and affects spikelet and grain number per spike. We identified a natural allele with positive effects on these two economically important traits. Loss-of-function mutations and natural variation in the gene FLOWERING LOCUS T2 (FT2) in wheat have previously been shown to affect spikelet number per spike (SNS). However, while other FT-like wheat proteins interact with bZIP-containing transcription factors from the A-group, FT2 does not interact with any of them. In this study, we used a yeast-two-hybrid screen with FT2 as bait and identified a grass-specific bZIP-containing transcription factor from the C-group, designated here as bZIPC1. Within the C-group, we identified four clades including wheat proteins that show Y2H interactions with different sets of FT-like and CEN-like encoded proteins. bZIPC1 and FT2 expression partially overlap in the developing spike, including the inflorescence meristem. Combined loss-of-function mutations in bZIPC-A1 and bZIPC-B1 (bzipc1) in tetraploid wheat resulted in a drastic reduction in SNS with a limited effect on heading date. Analysis of natural variation in the bZIPC-B1 (TraesCS5B02G444100) region revealed three major haplotypes (H1-H3), with the H1 haplotype showing significantly higher SNS, grain number per spike and grain weight per spike than both the H2 and H3 haplotypes. The favorable effect of the H1 haplotype was also supported by its increased frequency from the ancestral cultivated tetraploids to the modern tetraploid and hexaploid wheat varieties. We developed markers for the two non-synonymous SNPs that differentiate the bZIPC-B1b allele in the H1 haplotype from the ancestral bZIPC-B1a allele present in all other haplotypes. These diagnostic markers are useful tools to accelerate the deployment of the favorable bZIPC-B1b allele in pasta and bread wheat breeding programs.

Double DAP-seq uncovered synergistic DNA binding of interacting bZIP transcription factors

Many eukaryotic transcription factors (TF) form homodimer or heterodimer complexes to regulate gene expression. Dimerization of BASIC LEUCINE ZIPPER (bZIP) TFs are critical for their functions, but the molecular mechanism underlying the DNA binding and functional specificity of homo- versus heterodimers remains elusive. To address this gap, we present the double DNA Affinity Purification-sequencing (dDAP-seq) technique that maps heterodimer binding sites on endogenous genomic DNA. Using dDAP-seq we profile twenty pairs of C/S1 bZIP heterodimers and S1 homodimers in Arabidopsis and show that heterodimerization significantly expands the DNA binding preferences of these TFs. Analysis of dDAP-seq binding sites reveals the function of bZIP9 in abscisic acid response and the role of bZIP53 heterodimer-specific binding in seed maturation. The C/S1 heterodimers show distinct preferences for the ACGT elements recognized by plant bZIPs and motifs resembling the yeast GCN4 cis-elements. This study demonstrates the potential of dDAP-seq in deciphering the DNA binding specificities of interacting TFs that are key for combinatorial gene regulation.

Overexpression of the Brassica rapa bZIP Transcription Factor, BrbZIP-S, Increases the Stress Tolerance in Nicotiana benthamiana

In higher plants, S1-basic region-leucine zipper (S1-bZIP) transcription factors fulfill crucial roles in the physiological homeostasis of carbon and amino acid metabolisms and stress responses. However, very little is known about the physiological role of S1-bZIP in cruciferous vegetables. Here, we analyzed the physiological function of S1-bZIP from Brassica rapa (BrbZIP-S) in modulating proline and sugar metabolism. Overexpression of BrbZIP-S in Nicotiana benthamiana resulted in delayed chlorophyll degradation during the response to dark conditions. Under heat stress or recovery conditions, the transgenic lines exhibited a lower accumulation of H2O2, malondialdehyde, and protein carbonyls compared to the levels in transgenic control plants. These results strongly indicate that BrbZIP-S regulates plant tolerance against dark and heat stress. We propose that BrbZIP-S is a modulator of proline and sugar metabolism, which are required for energy homeostasis in response to environmental stress conditions.

Disrupting Sc-uORFs of a transcription factor bZIP1 using CRISPR/Cas9 enhances sugar and amino acid contents in tomato (Solanum lycopersicum)

Induced mutations in the SC-uORF of the tomato transcription factor gene SlbZIP1 by the CRISPR/Cas9 system led to the high accumulation of sugar and amino acid contents in tomato fruits. Tomato (Solanum lycopersicum) is one of the most popular and consumed vegetable crops in the world. Among important traits for tomato improvement such as yield, biotic and abiotic resistances, appearance, post-harvest shelf life and fruit quality, the last one seems to face more challenges because of its genetic and biochemical complexities. In this study, a dual-gRNAs CRISPR/Cas9 system was developed to induce targeted mutations in uORF regions of the SlbZIP1, a gene involved in the sucrose-induced repression of translation (SIRT) mechanism. Different induced mutations in the SlbZIP1-uORF region were identified at the T0 generation, stably transferred to the offspring, and no mutation was found at potential off-target sites. The induced mutations in the SlbZIP1-uORF region affected the transcription of SlbZIP1 and related genes in sugar and amino acid biosynthesis. Fruit component analysis showed significant increases in soluble solid, sugar and total amino acid contents in all SlbZIP1-uORF mutant lines. The accumulation of sour-tasting amino acids, including aspartic and glutamic acids, raised from 77 to 144%, while the accumulation of sweet-tasting amino acids such as alanine, glycine, proline, serine, and threonine increased from 14 to 107% in the mutant plants. Importantly, the potential SlbZIP1-uORF mutant lines with desirable fruit traits and no impaired effect on plant phenotype, growth and development were identified under the growth chamber condition. Our result indicates the potential utility of the CRISPR/Cas9 system for fruit quality improvement in tomato and other important crops.

S1-bZIP Transcription Factors Play Important Roles in the Regulation of Fruit Quality and Stress Response

Sugar metabolism not only determines fruit sweetness and quality but also acts as signaling molecules to substantially connect with other primary metabolic processes and, therefore, modulates plant growth and development, fruit ripening, and stress response. The basic region/leucine zipper motif (bZIP) transcription factor family is ubiquitous in eukaryotes and plays a diverse array of biological functions in plants. Among the bZIP family members, the smallest bZIP subgroup, S1-bZIP, is a unique one, due to the conserved upstream open reading frames (uORFs) in the 5' leader region of their mRNA. The translated small peptides from these uORFs are suggested to mediate Sucrose-Induced Repression of Translation (SIRT), an important mechanism to maintain sucrose homeostasis in plants. Here, we review recent research on the evolution, sequence features, and biological functions of this bZIP subgroup. S1-bZIPs play important roles in fruit quality, abiotic and biotic stress responses, plant growth and development, and other metabolite biosynthesis by acting as signaling hubs through dimerization with the subgroup C-bZIPs and other cofactors like SnRK1 to coordinate the expression of downstream genes. Direction for further research and genetic engineering of S1-bZIPs in plants is suggested for the improvement of quality and safety traits of fruit.

Genetic engineering of microalgae for enhanced lipid production

Microalgae have the potential to become microbial cell factories for lipid production. Their ability to convert sunlight and CO₂ into valuable lipid compounds has attracted interest from cosmetic, biofuel, food and feed industries. In order to make microalgae-derived products cost-effective and commercially competitive, enhanced growth rates and lipid productivities are needed, which require optimization of cultivation systems and strain improvement. Advances in genetic tool development and omics technologies have increased our understanding of lipid metabolism, which has opened up possibilities for targeted metabolic engineering. In this review we provide a comprehensive overview on the developments made to genetically engineer microalgal strains over the last 30 years. We focus on the strategies that lead to an increased lipid content and altered fatty acid profile. These include the genetic engineering of the fatty acid synthesis pathway, Kennedy pathway, polyunsaturated fatty acid and triacylglycerol metabolisms and fatty acid catabolism. Moreover, genetic engineering of specific transcription factors, NADPH generation and central carbon metabolism, which lead to increase of lipid accumulation are also reviewed.

Sugar and Nitrate Sensing: A Multi-Billion-Year Story

Sugars and nitrate play a major role in providing carbon and nitrogen in plants. Understanding how plants sense these nutrients is crucial, most notably for crop improvement. The mechanisms underlying sugar and nitrate sensing are complex and involve moonlighting proteins such as the nitrate transporter NRT1.1/NFP6.3 or the glycolytic enzyme HXK1. Major components of nutrient signaling, such as SnRK1, TOR, and HXK1, are relatively well conserved across eukaryotes, and the diversification of components such as the NRT1 family and the SWEET sugar transporters correlates with plant terrestrialization. In plants, Tre6P plays a hormone-like role in plant development. In addition, nutrient signaling has evolved to interact with the more recent hormone signaling, allowing fine-tuning of physiological and developmental responses.

Insight into the bZIP Gene Family in Solanum tuberosum: Genome and Transcriptome Analysis to Understand the Roles of Gene Diversification in Spatiotemporal Gene Expression and Function

The basic region-leucine zipper (bZIP) transcription factors (TFs) form homodimers and heterodimers via the coil–coil region. The bZIP dimerization network influences gene expression across plant development and in response to a range of environmental stresses. The recent release of the most comprehensive potato reference genome was used to identify 80 StbZIP genes and to characterize their gene structure, phylogenetic relationships, and gene expression profiles. The StbZIP genes have undergone 22 segmental and one tandem duplication events. Ka/Ks analysis suggested that most duplications experienced purifying selection. Amino acid sequence alignments and phylogenetic comparisons made with the Arabidopsis bZIP family were used to assign the StbZIP genes to functional groups based on the Arabidopsis orthologs. The patterns of introns and exons were conserved within the assigned functional groups which are supportive of the phylogeny and evidence of a common progenitor. Inspection of the leucine repeat heptads within the bZIP domains identified a pattern of attractive pairs favoring homodimerization, and repulsive pairs favoring heterodimerization. These patterns of attractive and repulsive heptads were similar within each functional group for Arabidopsis and S. tuberosum orthologs. High-throughput RNA-seq data indicated the most highly expressed and repressed genes that might play significant roles in tissue growth and development, abiotic stress response, and response to pathogens including Potato virus X. These data provide useful information for further functional analysis of the StbZIP gene family and their potential applications in crop improvement.

Fine-tuning sugar content in strawberry

Fine-tuning quantitative traits for continuous subtle phenotypes is highly advantageous. We engineer the highly conserved upstream open reading frame (uORF) of FvebZIPs1.1 in strawberry (Fragaria vesca), using base editor A3A-PBE. Seven novel alleles are generated. Sugar content of the homozygous T1 mutant lines is 33.9-83.6% higher than that of the wild-type. We also recover a series of transgene-free mutants with 35 novel genotypes containing a continuum of sugar content. All the novel genotypes could be immediately fixed in subsequent generations by asexual reproduction. Genome editing coupled with asexual reproduction offers tremendous opportunities for quantitative trait improvement.

Inferring the Evolutionary History of Your Favorite Protein: A Guide for Molecular Biologists

Comparative genomics has proven a fruitful approach to acquire many functional and evolutionary insights into core cellular processes. Here it is argued that in order to perform accurate and interesting comparative genomics, one first and foremost has to be able to recognize, postulate, and revise different evolutionary scenarios. After all, these studies lack a simple protocol, due to different proteins having different evolutionary dynamics and demanding different approaches. The authors here discuss this challenge from a practical (what are the observations?) and conceptual (how do these indicate a specific evolutionary scenario?) viewpoint, with the aim to guide investigators who want to analyze the evolution of their protein(s) of interest. By sharing how the authors draft, test, and update such a scenario and how it directs their investigations, the authors hope to illuminate how to execute molecular evolution studies and how to interpret them. Also see the video abstract here https://youtu.be/VCt3l2pbdbQ.

Metabolite Control of Translation by Conserved Peptide uORFs: The Ribosome as a Metabolite Multisensor

Ribosomes translate the mRNA code into protein, and this process can be controlled by metabolites that bind to the translating ribosome in interaction with the nascent protein.

HISTONE DEACETYLASE 9 stimulates auxin-dependent thermomorphogenesis in Arabidopsis thaliana by mediating H2A.Z depletion

Many plant species respond to unfavorable high ambient temperatures by adjusting their vegetative body plan to facilitate cooling. This process is known as thermomorphogenesis and is induced by the phytohormone auxin. Here, we demonstrate that the chromatin-modifying enzyme HISTONE DEACETYLASE 9 (HDA9) mediates thermomorphogenesis but does not interfere with hypocotyl elongation during shade avoidance. HDA9 is stabilized in response to high temperature and mediates histone deacetylation at the YUCCA8 locus, a rate-limiting enzyme in auxin biosynthesis, at warm temperatures. We show that HDA9 permits net eviction of the H2A.Z histone variant from nucleosomes associated with YUCCA8, allowing binding and transcriptional activation by PHYTOCHROME INTERACTING FACTOR 4, followed by auxin accumulation and thermomorphogenesis.

Novel pipeline identifies new upstream ORFs and non-AUG initiating main ORFs with conserved amino acid sequences in the 5' leader of mRNAs in Arabidopsis thaliana

Eukaryotic mRNAs contain a 5' leader sequence preceding the main open reading frame (mORF) and, depending on the species, 20%-50% of eukaryotic mRNAs harbor an upstream ORF (uORF) in the 5' leader. An unknown fraction of these uORFs encode sequence conserved peptides (conserved peptide uORFs, CPuORFs). Experimentally validated CPuORFs demonstrated to regulate the translation of downstream mORFs often do so in a metabolite concentration-dependent manner. Previous research has shown that most CPuORFs possess a start codon context suboptimal for translation initiation, which turns out to be favorable for translational regulation. The suboptimal initiation context may even include non-AUG start codons, which makes CPuORFs hard to predict. For this reason, we developed a novel pipeline to identify CPuORFs unbiased of start codon using well-annotated sequence data from 31 eudicot plant species and rice. Our new pipeline was able to identify 29 novel Arabidopsis thaliana (Arabidopsis) CPuORFs, conserved across a wide variety of eudicot species of which 15 do not initiate with an AUG start codon. In addition to CPuORFs, the pipeline was able to find 14 conserved coding regions directly upstream and in frame with the mORF, which likely initiate translation on a non-AUG start codon. Altogether, our pipeline identified highly conserved coding regions in the 5' leaders of Arabidopsis transcripts, including in genes with proven functional importance such as LHY, a key regulator of the circadian clock, and the RAPTOR1 subunit of the target of rapamycin (TOR) kinase.

Transcriptome and metabolome reveal distinct carbon allocation patterns during internode sugar accumulation in different sorghum genotypes

Sweet sorghum accumulates large amounts of soluble sugar in its stem. However, a system-based understanding of this carbohydrate allocation process is lacking. Here, we compared the dynamic transcriptome and metabolome between the conversion line R9188 and its two parents, sweet sorghum RIO and grain sorghum BTx406 that have contrasting sugar-accumulating phenotypes. We identified two features of sucrose metabolism, stable concentrations of sugar phosphates in RIO and opposite trend of trehalose-6-phosphate (T6P) between RIO vs R9188/BTx406. Integration of transcriptome and metabolome revealed R9188 is partially active in starch metabolism together with medium sucrose level, whereas sweet sorghum had the highest sucrose concentration and remained highly active in sucrose, starch, and cell wall metabolism post-anthesis. Similar expression pattern of genes involved in sucrose degradation decreased the pool of sugar phosphates for precursors of starch and cell wall synthesis in R9188 and BTx406. Differential T6P signal between RIO vs R9188/BTx406 is associated with introgression of T6P regulators from BTx406 into R9188, including C-group bZIP and trehalose 6-phosphate phosphatase (TPP). The inverted T6P signalling in R9188 appears to down-regulate sucrose and starch metabolism partly through transcriptome reprogramming, whereas introgressed metabolic genes could be related to reduced cell wall metabolism. Our results show that coordinated primary metabolic pathways lead to high sucrose demand and accumulation in sweet sorghum, providing us with targets for genetic improvements of carbohydrate allocation in bioenergy crops.

A Glycine soja group S2 bZIP transcription factor GsbZIP67 conferred bicarbonate alkaline tolerance in Medicago sativa

BACKGROUND

Even though bicarbonate alkaline stress is a serious threat to crop growth and yields, it attracts much fewer researches than high salinity stress. The basic leucine zipper (bZIP) transcription factors have been well demonstrated to function in diverse abiotic stresses; however, their biological role in alkaline tolerance still remains elusive. In this study, we functionally characterized a bZIP gene from Glycine soja GsbZIP67 in bicarbonate alkaline stress responses.

RESULTS

GsbZIP67 was initially identified as a putative bicarbonate responsive gene, on the basis of previous RNA-seq data of 50 mM NaHCO3-treated Glycine soja roots. GsbZIP67 protein possessed a conserved bZIP domain, and belonged to the group S2 bZIP, which is yet less well-studied. Our studies showed that GsbZIP67 targeted to nucleus in Arabidopsis protoplasts, and displayed transcriptional activation activity in yeast cells. The quantitative real-time PCR analyses unraveled the bicarbonate stress responsive expression and tissue specific expression of GsbZIP67 in wild soybean. Further phenotypic analysis illustrated that GsbZIP67 overexpression in alfalfa promoted plant growth under bicarbonate alkaline stress, as evidenced by longer roots and shoots. Furthermore, GsbZIP67 overexpression also modified the physiological indices of transgenic alfalfa under bicarbonate alkaline stress. In addition, the expression levels of several stress responsive genes were also augmented by GsbZIP67 overexpression.

CONCLUSIONS

Collectively, in this study, we demonstrated that GsbZIP67 acted as a positive regulator of plant tolerance to bicarbonate alkaline stress. These results provide direct genetic evidence of group S2 bZIPs in bicarbonate alkaline stress, and will facilitate further studies concerning the cis-elements and/or downstream genes targeted by GsbZIP67 in stress responses.

The Arabidopsis bZIP transcription factor family-an update

The basic (region) leucine zippers (bZIPs) are evolutionarily conserved transcription factors in eukaryotic organisms. Here, we have updated the classification of the Arabidopsis thaliana bZIP-family, comprising 78 members, which have been assorted into 13 groups. Arabidopsis bZIPs are involved in a plethora of functions related to plant development, environmental signalling and stress response. Based on the classification, we have highlighted functional and regulatory aspects of selected well-studied bZIPs, which may serve as prototypic examples for the particular groups.

The C/S1 bZIP Network: A Regulatory Hub Orchestrating Plant Energy Homeostasis

Sustaining energy homeostasis is crucial to every living being. To balance energy supply and demand, plants make use of an evolutionarily conserved management system consisting of two counteracting kinases, TOR (TARGET OF RAPAMYCIN) and SnRK1 (Snf1-RELATED PROTEIN KINASE 1). SnRK1 is involved in reorganizing enzymatic and transcriptional responses to survive energy-limiting conditions. Recently, members of the bZIP (basic leucine zipper) transcription factor family have been established as SnRK1 downstream mediators. We review here current knowledge on the functional impact of these group C and S₁ bZIPs, and analyze their regulation by environmental and endogenous cues. Given their specific homo- and heterodimerization, the so-called C/S₁ bZIP network is proposed to act as a signaling hub that coordinates plant development and stress responses.

Enhancement of biomass and lipid productivity by overexpression of a bZIP transcription factor in Nannochloropsis salina

Microalgae are considered as excellent platforms for biomaterial production that can replace conventional fossil fuel-based fuels and chemicals. Genetic engineering of microalgae is prerequisite to maximize production of materials and to reduce costs for the production. Transcription factors (TFs) are emerging as key regulators of metabolic pathways to enhance production of molecules for biofuels and other materials. TFs with the basic leucine zipper (bZIP) domain have been known as stress regulators and are associated with lipid metabolism in plants. We overexpressed a bZIP TF, NsbZIP1, in Nannochloropsis salina, and found that transformants showed enhanced growth with concomitant increase in lipid contents. The improved phenotypes were also notable under stress conditions including N limitation and high salt. To understand the mechanism underlying improved phenotypes, we analyzed expression patterns of predicted target genes involved in lipid metabolism via quantitative RT-PCR, confirming increases transcript levels. NsbZIP1 appeared to be one of type C bZIPs in plants that has been known to regulate lipid metabolism under stress. Taken together, we demonstrated that NsbZIP1 could improve both growth and lipid production, and TF engineering can serve as an excellent genetic engineering tool for production of biofuels and biomaterials in microalgae.

Genome-Wide Identification and Structural Analysis of bZIP Transcription Factor Genes in Brassica napus

The basic region/leucine zipper motif (bZIP) transcription factor family is one of the largest families of transcriptional regulators in plants. bZIP genes have been systematically characterized in some plants, but not in rapeseed (Brassica napus). In this study, we identified 247 BnbZIP genes in the rapeseed genome, which we classified into 10 subfamilies based on phylogenetic analysis of their deduced protein sequences. The BnbZIP genes were grouped into functional clades with Arabidopsis genes with similar putative functions, indicating functional conservation. Genome mapping analysis revealed that the BnbZIPs are distributed unevenly across all 19 chromosomes, and that some of these genes arose through whole-genome duplication and dispersed duplication events. All expression profiles of 247 bZIP genes were extracted from RNA-sequencing data obtained from 17 different B. napus ZS11 tissues with 42 various developmental stages. These genes exhibited different expression patterns in various tissues, revealing that these genes are differentially regulated. Our results provide a valuable foundation for functional dissection of the different BnbZIP homologs in B. napus and its parental lines and for molecular breeding studies of bZIP genes in B. napus.