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The new variety Betula pendula 'Dalecarlica', selected from Betula pendula , shows high ornamental value owing to its lobed leaf shape. In this study, to identify the genetic components of leaf shape formation, we performed bulked segregant analysis and molecular marker-based fine mapping to identify the causal gene responsible for lobed leaves in B. pendula 'Dalecarlica'. The most significant variations associated with leaf shape were identified within the gene BpPIN1 encoding a member of the PIN-FORMED family, responsible for the auxin efflux carrier. We further confirmed the hypomethylation at the promoter region promoting the expression level of BpPIN1 , which causes stronger and longer veins and lobed leaf shape in B. pendula 'Dalecarlica'. These results indicated that DNA methylation at the BpPIN1 promoter region is associated with leaf shapes in B. pendula. Our findings revealed an epigenetic mechanism of BpPIN1 in the regulation of leaf shape in Betula   Linn. (birch), which could help in the molecular breeding of ornamental traits. [ABSTRACT FROM AUTHOR]

This article discusses the establishment of a high-efficiency genome editing system in white birch trees. The researchers aimed to optimize the genome editing system in white birch to address the challenges of climate change and growing societal demands. They conducted a screening process using a superior white birch strain and tested different endogenous promoters to drive sgRNA expression. The study found that the efficiency of genome editing varied depending on the promoters used, with endogenous promoters showing higher editing efficiencies compared to exogenous promoters. The findings provide valuable support for the development of a multiple-gene editing system and molecular breeding in white birch and other forest trees. [Extracted from the article]

Background: The TIFY family is a plant-specific gene family and plays an important role in plant growth and development. But few reports have been reported on the phylogenetic analysis and gene expression profiling of TIFY family genes in birch (Betula platyphylla). Results: In this study, we characterized TIFY family and identified 12 TIFY genes and using phylogeny and chromosome mapping analysis in birch. TIFY family members were divided into JAZ, ZML, PPD and TIFY subfamilies. Phylogenetic analysis revealed that 12 TIFY genes were clustered into six evolutionary branches. The chromosome distribution showed that 12 TIFY genes were unevenly distributed on 5 chromosomes. Some TIFY family members were derived from gene duplication in birch. We found that six JAZ genes from JAZ subfamily played essential roles in response to Methyl jasmonate (MeJA), the JAZ genes were correlated with COI1 under MeJA. Co-expression and GO enrichment analysis further revealed that JAZ genes were related to hormone. JAZ proteins involved in the ABA and SA pathways. Subcellular localization experiments confirmed that the JAZ proteins were localized in the nucleus. Yeast two-hybrid assay showed that the JAZ proteins may form homologous or heterodimers to regulate hormones. Conclusion: Our results provided novel insights into biological function of TIFY family and JAZ subfamily in birch. It provides the theoretical reference for in-depth analysis of plant hormone and molecular breeding design for resistance. [ABSTRACT FROM AUTHOR]

Plant polyploidization changes its leaf morphology and leaf development patterns. Understanding changes in leaf morphology and development patterns is a prerequisite and key to studying leaf development in polyploid plants. In this study, we quantified and analyzed the differences in leaf morphology, leaf growth polarity, and leaf size between diploid and tetraploid birches (Betula pendula subsp. pendula), and preliminarily investigated genes involved in leaf growth and development in birch. The results showed significant changes in leaf morphology in tetraploid birches, especially the basal part of the leaf. In addition, the proximal growth rate of tetraploid leaves was altered. The changed proximal growth rate did not affect the growth polarity pattern of tetraploid leaves. The leaf area of tetraploid was significantly larger than that of diploid birch. The difference in leaf size was mainly due to differences in their growth rates in the middle and late stages of leaf development. Increased cell expansion capacity was the major reason for the enormous leaves of tetraploid birch; however, cell proliferation did not contribute to the larger tetraploid leaf. The gene expression of ATHB12 was associated with cell size and leaf area, and may be a critical gene affecting the leaf size in diploid and tetraploid birches. The results will provide valuable insights into plant polyploid leaf development and a theoretical basis for later investigations into the molecular mechanisms underlying the gigantism of tetraploid birch leaves. [ABSTRACT FROM AUTHOR]

Drought stress causes various negative impacts on plant growth and crop production. R2R3-MYB transcription factors (TFs) play crucial roles in the response to abiotic stress. However, their functions in Betula platyphylla haven't been fully investigated. In this study, a R2R3 MYB transcription factor gene, BpMYB123 , was identified from Betula platyphylla and reveals its significant role in drought stress. Overexpression of BpMYB123 enhances tolerance to drought stress in contrast to repression of BpMYB123 by RNA interference (RNAi) in transgenic experiment. The overexpression lines increased peroxidase (POD) and superoxide dismatase (SOD) activities, while decreased hydrogen peroxide (H2O2), superoxide radicals (O2–), electrolyte leakage (EL) and malondialdehyde (MDA) contents. Our study showed that overexpression of BpMYB123 increased BpLEA14 gene expression up to 20-fold due to BpMYB123 directly binding to the MYB1AT element of BpLEA14 promoter. These results indicate that BpMYB123 acts as a regulator via regulating BpLEA14 to improve drought tolerance in birch. [ABSTRACT FROM AUTHOR]

PP2C protein phosphatase family is one of the largest gene families in the plant genome. Many PP2C family members are involved in the regulation of abiotic stress. We found that BpPP2C1 gene has highly up-regulated in root under salt stress in Betula platyphylla. Thus, transgenic plants of Betula platyphylla with overexpression and knockout of BpPP2C1 gene were generated using a zygote transformation system. Under NaCl stress treatment, we measured the phenotypic traits of transgenic plants, chlorophyll-fluorescence parameters, peroxidase (POD) activity, superoxide dismutase (SOD) activity, and malondialdehyde (MDA) content. We found that BpPP2C1 overexpressed lines showed obvious salt tolerance, while BpPP2C1 knocked out plants were sensitive to salt stress. Transcriptome analysis identified significantly amount of differentially expressed genes associated with salt stress in BpPP2C1 transgenic lines, especially genes in abscisic acid signaling pathway, flavonoid biosynthetic pathway, oxidative stress and anion transport. Functional study of BpPP2C1 in Betula platyphylla revealed its role in salt stress. [ABSTRACT FROM AUTHOR]

Flowering is a crucial process for plants that is under complex genetic control. AP1 acts as an organizer and a switch for the transition from vegetative to reproductive growth. In our previous study, we found that overexpression of BpAP1 significantly promoted the formation of male inflorescence in birch (Betula platyphlla × B. pendula). In this study, we aimed at investigating the molecular regulatory mechanism of BpAP1 during the process of male inflorescence formation in birch. We found that overexpression of BpAP1 affected the expression of many flowering-related genes, and had significant effect on B class MADS-box genes. A BpAP1-mediated gene regulatory network was constructed and B class gene BpDEF was finally predicted as a key target gene of BpAP1. Chromatin immunoprecipitation results indicated that BpAP1 could directly regulate BpDEF during the process of male inflorescence formation. Yeast one-hybrid assays and its validation in tobacco results suggested that BpAP1 regulated BpDEF via binding to a consensus DNA sequence known as CArG box. Gene function analysis of BpDEF indicated that BpDEF may function in sex-determination, and in particular specify the identity of male inflorescence in birch. Our results provide valuable clues for our understanding of the molecular mechanism of BpAP1 during the process of male inflorescence formation in birch. [ABSTRACT FROM AUTHOR]

Birch (Betula platyphylla × B. pendula) is an important tree for landscaping due to its attractive white bark and straight trunk. In this study, we characterized a T-DNA yellow-green leaf mutant, yl. We identified six insertion sites (ISs) in the mutant by genome resequencing and found a 40-kb deletion containing BpGLK1 around IS2 on chromosome 2. Complementation experiments with the yl mutant and repression of BpGLK1 in wild-type plants confirmed that BpGLK1 was responsible for the mutated phenotype. Physiological and ultrastructural analyses showed that the leaves of the yl mutant and BpGLK1 -repression lines had decreased chlorophyll content and defective chloroplast development compared to the wild-type. Furthermore, the loss function of BpGLK1 also affected photosynthesis in leaves. Transcriptomics, proteomics, and ChIP-PCR analysis revealed that BpGLK1 directly interacted with the promoter of genes related to antenna proteins, chlorophyll biosynthesis, and photosystem subunit synthesis, and regulated their expression. Overall, our research not only provides new insights into the mechanism of chloroplast development and chlorophyll biosynthesis regulated by BpGLK1 , but also provides new transgenic birch varieties with various levels of yellowing leaves by repressing BpGLK1 expression. [ABSTRACT FROM AUTHOR]

Growth characteristics have a complex inheritance pattern, and gene-environment interactions make predicting tree responses to environmental change difficult. In this study, we planted 44 Betula platyphylla families at three different sites (Mao er shan forestry center in Shangzhi, Jilin experiment forestry center in Jilin, Lang xiang forestry center in Langxiang) in northeastern China. Variation and stability of genotype-environment interactions of different families were analyzed using additive main effect and multiplicative interaction models. Variation analysis indicated significant differences between site × family interaction mean values for height, diameter at breast height, volume, and stem straight degree, suggesting that most genotypes responded differently according to location. The phenotypic coefficients of variation of different traits ranged from 12.84 % (stem straight degree in Langxiang) to 53.34 % (volume in Langxiang) and heritabilities of the different traits varied from 0.485 (diameter at breast height in Mao er shan) to 0.781 (height in Jilin). Correlation analysis showed a significantly positive association between tree height, diameter at breast height, and volume at the same and different sites, but stem straight degree showing a weaker correlation with other traits. Stability analysis indicated that some families had high tree heights but were sensitive to environmental conditions, whereas others had average tree heights but were resistant to environmental conditions. These results suggest that families should be bred in various habitats to assess growth under favorable and unfavorable environments. Under a selection ratio of 10 %, four families (family 1-7, 4-7, 3-12 and 4-13) were rated as superior families. The average height, diameter at breast height, volume, and stem straight degree of these four families were higher than average of all the families by 12.24, 16.82, 32.28 and 6.28 % in the four test sites, respectively. [ABSTRACT FROM AUTHOR]

The study utilized the offspring of a 5 × 5 diallel cross of Betula platyphylla as the experimental material. Tree height (H), diameter at breast height (DBH) and stem straight degree (SSD) were measured at the fourth and eighth growth year (SSD were measured only in the eighth growth year). ANOVA analyses showed that growth traits in different growth years were significant among families ( P < 0.01). There existed extremely significant correlations between H and DBH in the same year. Although the sequencing of average H and DBH of different families were vicissitudinous at the 4th and 8th year, there also existed significant correlations between H and DBH in different year. The general combining ability, special combining ability (SCA) and reciprocal effect (REC) of different hybridized combinations were also different remarkably. The mean square of SCA was significantly higher than GCA, implied that the non-additive effect played major roles. When B5, B8 and MB15 were selected as parents, the offspring performed perfectly in traits of H, DBH and SSD at the eighth growth year respectively. B5 × XB11, B8 × XB11 and B8 × MB15 had highest SCA values in traits of H, DBH, and SSD at the eighth growth year respectively. Consequently, in order to achieve optimal outcomes, seed orchard building and clonal propagation should be considered simultaneously in birch's genetic improvement process. [ABSTRACT FROM AUTHOR]

Background: Plant architecture, which is mostly determined by shoot branching, plays an important role in plant growth and development. Thus, it is essential to explore the regulatory molecular mechanism of branching patterns based on the economic and ecological importance. In our previous work, a multiple-branches birch mutant br was identified from 19 CINNAMOYL-COENZYME A REDUCTASE 1 (CCR1)-overexpressed transgenic lines, and the expression patterns of differentially expressed genes in br were analyzed. In this study, we further explored some other characteristics of br, including plant architecture, wood properties, photosynthetic characteristics, and IAA and Zeatin contents. Meanwhile, the T-DNA insertion sites caused by the insertion of exogenous BpCCR1 in br were identified to explain the causes of the mutation phenotypes. Results: The mutant br exhibited slower growth, more abundant and weaker branches, and lower wood basic density and lignin content than BpCCR1 transgenic line (OE2) and wild type (WT). Compared to WT and OE2, br had high stomatal conductance (Gs), transpiration rate (Tr), but a low non-photochemical quenching coefficient (NPQ) and chlorophyll content. In addition, br displayed an equal IAA and Zeatin content ratio of main branches' apical buds to lateral branches' apical buds and high ratio of Zeatin to IAA content. Two T-DNA insertion sites caused by the insertion of exogenous BpCCR1 in br genome were found. On one site, chromosome 2 (Chr2), no known gene was detected on the flanking sequence. The other site was on Chr5, with an insertion of 388 bp T-DNA sequence, resulting in deletion of 107 bp 5′ untranslated region (UTR) and 264 bp coding sequence (CDS) on CORONATINE INSENSITIVE 1 (BpCOII). In comparison with OE2 and WT, BpCOI1 was down-regulated in br, and the sensitivity of br to Methyl Jasmonate (MeJA) was abnormal. Conclusions: Plant architecture, wood properties, photosynthetic characteristics, and IAA and Zeatin contents in main and lateral branches' apical buds changed in br over the study's time period. One T-DNA insertion was identified on the first exon of BpCOI1, which resulted in the reduction of BpCOI1 expression and abnormal perception to MeJA in br. These mutation phenotypes might be associated with a partial loss of BpCOI1 in birch. [ABSTRACT FROM AUTHOR]

To investigate the molecular mechanism of the mutation of a multiple-branches birch mutant (br), we explored genes that were genome-wide differentially expressed in the main and lateral branches' apical buds of br. The plant architecture not only has effects on the process of plant growth and development, but also affects the agronomic characters. In woody plants, branches determine the application value of timber. Therefore, analyzing genes that were differentially expressed in br apical buds will bring new insights to understand the molecular basis of plant architecture alteration. Wild type (WT) birch, Cinnamoyl-CoA reductase 1 (CCR1)-overexpressed transgenic birch (OE2) and the mutant br were used as materials to observe phenotype differences between br and the control lines (WT and OE2). The transcriptome sequencing of the main and lateral branches' apical buds of br and controls were further performed to explore genes that were genome-wide differentially expressed in br. Compared to the control lines, br exhibited a multiple-branches and dwarf phenotype. In addition, biomass, rooting number, leaf area, internal diameter, and external diameter of stomata, and the size of terminal buds of br were less than that of WT and OE2. Transcriptome analysis results indicated that gene expression profiles of br were different from the control lines. The genes that were differentially expressed in br apical buds were involved in multiple pathways, including organogenesis, fertility regulation, cell division and differentiation, plant hormone biosynthesis, and signal transduction. The multiple-branches, dwarf, and small leaves and buds of br might be due to the differentially expressed genes (DEGs) involved in organogenesis, cell division and differentiation, plant hormone biosynthesis and signal transduction. [ABSTRACT FROM AUTHOR]

Chlorophyll (Chl)-deficient mutants are ideal materials for the study of Chl biosynthesis, chloroplast development, and photosynthesis. Although the genes encoding key enzymes related to Chl biosynthesis have been well-characterized in herbaceous plants, rice (Oryza sativa L.), Arabidopsis (Arabidopsis thaliana), and maize (Zea mays L.), yellow-green leaf mutants have not yet been fully studied in tree species. In this work, we explored the molecular mechanism of the leaf color formation in a yellow-green leaf mutant (yl). We investigated the differentially expressed genes (DEGs) between yl and control plants (wild type birch (WT) and BpCCR1 overexpression line 11, (C11)) by transcriptome sequencing. Approximately 1163 genes (874 down-regulated and 289 up-regulated) and 930 genes (755 down-regulated and 175 up-regulated) were found to be differentially expressed in yl compared with WT and C11, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis for DEGs revealed that photosynthesis antenna proteins represent the most significant enriched pathway. The expressions of photosynthesis antenna proteins are crucial to the leaf color formation in yl. We also found that Chl accumulate, leaf anatomical structure, photosynthesis, and growth were affected in yl. Taken together, our results not only provide the difference of phenomenal, physiological, and gene expression characteristics in leaves between yl mutant and control plants, but also provide a new insight into the mutation underlying the chlorotic leaf phenotype in birch. [ABSTRACT FROM AUTHOR]

Abstract: Plant researchers have focused much attention on leaf shape because of its importance in the identification. To evaluate the impact of intraspecies leaf-shape variation on the transcriptome, a series of Betula pendula ‘Dalecarlica’ and B. pendula saplings were generated through tissue culture. The leaf shapes and transcriptomes of B. pendula ‘Dalecarlica’ clones were compared with those of B. pendula clones. The leaf shape of B. pendula ‘Dalecarlica’ was incised and that of B. pendula was ovate. Transcriptome data revealed numerous changes in gene expression between B. pendula ‘Dalecarlica’ and B. pendula, including upregulation of 8767 unigenes and downregulation of 8379 unigenes in B. pendula ‘Dalecarlica’. A pathway analysis revealed that the transport and signal transduction of auxin were altered in ‘Dalecarlica’, which may have contributed to its altered leaf shape. These results shed light on variation in birch leaf shape and help identify important genes for the genetic engineering of birch trees. [Copyright &y& Elsevier]

Plants interact with biotic and abiotic environments. Some of these interactions are detrimental including herbivory consumption and infections by microbial pathogens. The COI1 (coronatine insensitive 1) protein is the master controller of JA-regulated plant responses and plays a regulatory role in the plant defense response. However, there is little information on COI1 function in birch (Betula platyphylla × Betula pendula). Herein, we studied the F-box protein BpCOI1 which is located in the nucleus. To validate the function of this protein, we developed transgenic birch plants with overexpression or repression of BpCOI1 gene. Growth traits, such as tree height, ground diameter, number of lateral branches, did not change significantly among transgenic lines. Alternaria alternata treatment experiments indicated that low expression of BpCOI1 reduced disease resistance in birch. Furthermore, our results showed that low expression of BpCOI1 significantly reduced the sensitivity of plants to exogenous MeJA. Co-expression analysis showed gene expression patterns with similar characteristics. These genes may be closely related in function, or members involved in the same signaling pathway or physiological process with BpCOI 1. The results of transcriptome sequencing and co-expression analysis showed that BpCOI1 affects plant defense against Alternaria alternata by regulating jasmonates. This study reveals the role of BpCOI1 in disease resistance and proposes the possibility of controlling diseases through molecular breeding in birch. • We obtained transgenic birch lines that overexpress and suppress BpCOI1 gene. • The inhibition gene expression of BpCOI1 resulted in significantly increasing Alternaria alternata infection. • The inhibition expression of COI1 results in insensitive responsive to MeJA. • The COI1 affects the defense of plants against external organisms by regulating JA signal pathway. [ABSTRACT FROM AUTHOR]

Leaf senescence and abscission play crucial role in annual plant adapting to seasonal alteration and climate changes by shortening life cycle and development process in response to abiotic and/or biotic stressors underlying phytohormones and environmental signals. Ethylene and abscisic acid are the major phytohormones that promotes leaf senescence, involving various transcription factors, such as EIN3 (ethylene-insensitive 3) and EIL (ethylene-insensitive 3-like) gene family, controlling leaf senescence through metabolite biosynthesis and signal transduction pathways. However, the roles of EIN3 regulating leaf senescence responding to environmental changes in perennial plant, especially forestry tree, remain unclear. In this study, we found that BpEIN3.1 from a subordinated to EIL3 subclade, is a transcription repressor and regulated light-dependent premature leaf senescence in birch (Betula platyphylla). BpEIN3.1 might inhibits the transcription of BpATPS1 by binding to its promoter. Shading suppressed premature leaf senescence in birch ein3.1 mutant line. Ethylene and abscisic acid biosynthesis were also reduced. In addition, abscisic acid positively regulated the expression of BpEIN3.1. This was demonstrated by the hormone-response element analysis of BpEIN3.1 promoter and its gene expression after the hormone treatments. Moreover, our results showed that abscisic acid is also involved in maintaining homeostasis. The molecular mechanism of leaf senescence provides a possibility to increasing wood production by delaying of leaf senescence. • Function of BpEIN3.1 regulating leaf senescence in Betula platyphylla was analyzed. • BpEIN3.1 served in inhibition of ethylene and abscisic acid biosynthesis, which delayed leaf senescence. • Light affects leaf senescence of plants. [ABSTRACT FROM AUTHOR]

• A birch ERF transcription factor, BpERF13 , which positively responds and regulates cold stress, was cloned and functionally characterized. • Transgenic lines overexpressing BpERF13 exhibited normal phenotypes except for a significantly augmented tolerance to cold stress. • BpERF13 augmented cold tolerance in transgenic lines through upregulating two CBF genes and four reactive oxygen species scavenging genes. The AP2/ERF (APETALA2/ethylene-responsive factor) family of transcription factors (TF) is involved in regulating biotic and abiotic stress responses in plants. To explore the role of AP2/ERFs in cold tolerance in woody plants, BpERF13 was cloned and characterized in Betula platyphylla (white birch), a species primarily found in Asia in temperate and boreal climates. Based on phylogenetic analysis, BpERF13 is a member of the IXb subfamily of ERFs. Using qRT-PCR, we found that BpERF13 was differentially expressed in different tissues, and its expression could be induced by cold treatment (4 °C). BpERF13 protein, fused with GFP, was exclusively localized to nuclei. To further assess the role of BpERF13 in cold tolerance, BpERF13 overexpression (OE) transgenic lines were generated in B. platyphylla and used for cold stress treatment and biochemical/physiological studies. BpERF13 overexpression lines had significantly increased tolerance to subfreezing treatment and reduced reactive oxygen species. Using a TF-centered yeast one-hybrid (Y1H) experimental system, we showed that BpERF13 could bind to LTRECOREATCOR15 and MYBCORE cis-elements to activate a reporter gene. ChIP-seq and ChIP-PCR experiments further demonstrated that BpERF13 bound to these cis-elements when present in the 5′ proximal regions of superoxide dismutase (SOD), peroxidase (POD), and C-repeat-binding factor (CBF) genes. qRT-PCR was employed to examine the expression levels of these genes in response to cold stress; SOD, POD, and CBF genes were significantly upregulated in BpERF13 transgenic lines compared to wild-type plants in response to cold stress. These results indicate that the transcription factor BpERF13 regulates physiological processes underlying cold tolerance in woody plants. [ABSTRACT FROM AUTHOR]

• BpAP1 activates BpPI expression via directly binding to a consensus motif that is known as CArG box. • BpPI could also bind to the promoter of BpAP1 to restrict BpAP1 expression. • BpDEF, a hypothetical partner of BpPI, could form a heterodimer with BpPI to directly restrict BpAP1 in birch. • Our results indicate that this is a negative feedback loop between BpAP1 and BpPI/BpDEF heterodimer in Betula platyphylla × B. pendula. MADS-box genes encode transcription factors involved in the control of many important developmental processes, especially the flower development of angiosperms. Analysis on gene regulatory relationship between MADS-box genes is useful for understanding the molecular mechanism of flower development. In this study, we focused on the regulatory relationship between MADS-box transcription factors APETALA1 (AP1) and PISTILLATA(PI)/DEFICIENS (DEF) in birch. We found that BpPI was an authentic target gene of BpAP1, and BpAP1 activated the expression of BpPI via directly binding to the CArG box motif. Functional analysis of BpPI showed that overexpression of BpPI may delay flowering via restricting flowering activators, in which BpAP1 was significantly down-regulated. We further investigated the regulatory of BpAP1 by BpPI, and found that BpPI could directly bind to the promoter of BpAP1 to restrict BpAP1 expression. In addition, we also found that BpPI could interact with its hypothetical partner BpDEF to co-regulate BpAP1 in birch. Our results suggested that overexpression of BpPI may delay flowering via restricting flowering activators, and there is a negative feedback loop between BpAP1 and BpPI/BpDEF heterodimer in birch. Our results will bring new evidences for further analysis of the molecular mechanism of flower formation in plants that produced unisexual flowers. [ABSTRACT FROM AUTHOR]