Embryogenic callus induction from immature zygotic embryos and genetic transformation of Larix kaempferi 3x Larix gmelinii 9

Isolation and Expression Pattern Analysis of Larix olgensis LoNAC5: LoNAC5 Acts as a Positive Regulator of Drought and Salt Tolerance

NAC transcription factors are a kind of plant specific transcription factor widely distributed in plants, and they play an important role in the process of plant growth and development. According to the transcriptome data, a transcription factor with typical NAC characteristics was isolated from Larix olgensis (common name "Dahurian larch"), that we named LoNAC5. The length of the coding sequence (CDS) was 1164 bp, encoding 387 amino acids. The LoNAC5 protein harbors a NAM (NAC family) domain at the 14-139 aa region of its N-terminus and an activation domain at the 324-364 aa region of the C-terminus. Phylogenetic tree analysis revealed that LoNAC5 belonged to the ATNAC3 subgroup. Cis-acting element analysis showed that there were multiple plant stress-resistance-related elements on the promoter of LoNAC5, including hormone and light responsiveness elements. LoNAC5 was localized in the nucleus by injection transformation of tobacco leaves. Results suggested that the LoNAC5 protein is active as a homodimer and that it binds to the GATGTG motif. The results of RT-qPCR showed that LoNAC5 is a highly expressed gene in L. olgensis, and the expression level is highest in 180-day needles. LoNAC5 responded to various hormone treatments and was induced by drought and salt stress. The yeast phenotype test showed that overexpression of LoNAC5 could make yeast grow better under drought and salt stress. It was speculated that LoNAC5 might act in L. olgensis as a positive regulator of drought and salt tolerance.

Overexpression of Lol-miR11467 negatively affects osmotic resistance in Larix kaempferi 3 × L. gmelinii 9

BACKGROUND

Larch (Larix gmelinii (Rupr.) Kuzen.) is an important timber and ecological tree species in northern China. Excellent germplasm resources have been acquired through time-consuming traditional breeding. Molecular breeding offers a promising approach to shorten the breeding cycle and achieve genetic improvements more efficiently. MicroRNAs (miRNAs) are non-coding, single-stranded small RNAs that primarily affect plant growth and stress resistance, including drought stress. However, the study of miRNAs in larch under drought stress has not been well explored.

RESULTS

In this study, to investigate the function of Lol-miR11467 under PEG osmotic stress in larch, embryogenic callus tissue of Larix kaempferi 3 × L. gmelinii 9 was employed as the experimental material, serving as the explants for this study. Lol-miR11467 was transferred into the explants using an Agrobacterium-mediated method to determine the physiological changes and survey gene expression changes in overexpressing Lol-miR11467 cell lines. The results showed that the fresh weight, peroxidase (POD), soluble protein and soluble sugar content of the overexpressing Lol-miR11467 were lower than that of the wild-type, while malondialdehyde (MDA) content increased under PEG osmotic stress. Transcriptome analysis showed that genes associated with phenylpropanoid metabolism, transcription factors, oxidoreductase, plant hormone signal transduction, glucose metabolism and bioprotective macromolecules were mainly downregulated in Lol-miR11467 cell lines.

CONCLUSIONS

Overall, these results indicated that the drought resistance of the overexpressing Lol-miR11467 cell lines was reduced. This study's findings might provide a foundation for understanding the molecular mechanisms of miRNAs under PEG osmotic stress in larch, potentially contributing to the development of strategies for improving plant resilience to environmental stresses.

Screening and Functional Evaluation of Four Larix kaempferi Promoters

Promoters are powerful tools for breeding new varieties using transgenic technology. However, the low and unstable expression of target genes is still a limiting factor in Larix kaempferi (Lamb.) Carr (Japanese larch) genetic transformation. In this study, we analyzed L. kaempferi transcriptome data, screened out highly expressed genes, cloned their promoters, and constructed plant expression vectors containing the β-glucuronidase (GUS) reporter gene driven by these promoters. Recombinant vectors were introduced into the L. kaempferi embryogenic callus by means of the Agrobacterium-mediated transient or stable genetic transformation method, and the promoter activity was then determined by measuring GUS expression and its enzyme activity in the transformed materials. Four highly expressed genes were identified: L. kaempferi Zhang Chen Yi-1 (LaZCY-1), Zhang Chen Yi-2 (LaZCY-2), Translationally Controlled Tumor Protein (LaTCTP), and ubiquitin (LaUBQ). The 2000 bp fragments upstream of ATG in these sequences were cloned as promoters and named pLaZCY-1, pLaZCY-2, pLaTCTP, and pLaUBQ. Semi-quantitative and quantitative RT-PCR analyses of transient genetic transformation materials showed that all four promoters could drive GUS expression, indicating that they have promoter activities. Semi-quantitative and quantitative RT-PCR analyses and the histochemical staining of stable genetic transformation materials showed that the pLaUBQ promoter had higher activity than the other three L. kaempferi promoters and the CaMV35S promoter. Thus, the pLaUBQ promoter was suggested to be used in larch genetic transformation.

Genetic transformation in conifers: current status and future prospects

Genetic transformation has been a cornerstone in plant molecular biology research and molecular design breeding, facilitating innovative approaches for the genetic improvement of trees with long breeding cycles. Despite the profound ecological and economic significance of conifers in global forestry, the application of genetic transformation in this group has been fraught with challenges. Nevertheless, genetic transformation has achieved notable advances in certain conifer species, while these advances are confined to specific genotypes, they offer valuable insights for technological breakthroughs in other species. This review offers an in-depth examination of the progress achieved in the genetic transformation of conifers. This discussion encompasses various factors, including expression vector construction, gene-delivery methods, and regeneration systems. Additionally, the hurdles encountered in the pursuit of a universal model for conifer transformation are discussed, along with the proposal of potential strategies for future developments. This comprehensive overview seeks to stimulate further research and innovation in this crucial field of forest biotechnology.

Primary Metabolite Screening Shows Significant Differences between Embryogenic and Non-Embryogenic Callus of Tamarillo (Solanum betaceum Cav.)

Tamarillo is a solanaceous tree that has been extensively studied in terms of in vitro clonal propagation, namely somatic embryogenesis. In this work, a protocol of indirect somatic embryogenesis was applied to obtain embryogenic and non-embryogenic callus from leaf segments. Nuclear magnetic resonance spectroscopy was used to analyze the primary metabolome of these distinct calli to elucidate possible differentiation mechanisms from the common genetic background callus. Standard multivariate analysis methods were then applied, and were complemented by univariate statistical methods to identify differentially expressed primary metabolites and related metabolic pathways. The results showed carbohydrate and lipid metabolism to be the most relevant in all the calli assayed, with most discriminant metabolites being fructose, glucose and to a lesser extent choline. The glycolytic rate was higher in embryogenic calli, which shows, overall, a higher rate of sugar catabolism and a different profile of phospholipids with a choline/ethanolamine analysis. In general, our results show that a distinct primary metabolome between embryogenic and non-embryogenic calli occurs and that intracellular levels of fructose and sucrose and the glucose to sucrose ratio seem to be good candidates as biochemical biomarkers of embryogenic competence.

Efficient organogenesis and taxifolin production system from mature zygotic embryos and needles in larch

The deciduous conifer larch has been widely distributed around the world, is a high-quality wood species and is also used to extract industrial raw materials and medicines. In this study, we developed an organogenesis protocol for Larix olgensis from both mature zygotic embryos and needles, and analyzed the content of taxifolin in different tissues. The highest callus induction (96.8%) from mature zygotic embryo was found in the Douglas-fir Cotyledon Revised (DCR) medium augmented with 2.0 mg·L -1 6-Benzylaminopurine (6-BA) and 0.2 mg·L -1 α-Naphthaleneacetic acid (NAA), while from needles the highest callus induction (92.03%) was found in the Murashige and Skoog (MS) medium augmented with 3 mg·L -1 6-BA and 0.3 mg·L -1 NAA. The best shoot regeneration capacity from zygotic embryo-derived calli (83.3%) was obtained in DCR medium augmented with 1.0 mg·L -1 6-BA and 0.01 mg·L -1 NAA, and needle-derived calli were 77.3%. The shoots achieved the highest elongation (75.6%) in the DCR medium supplemented with 0.5 mg·L -1 6-BA, 0.05 mg·L -1 NAA and 2 g·L -1 activated charcoal (AC). The rooting rate was 62.8% in DCR medium augmented with 3 mg·L -1 Indole-3-butyric acid (IBA) and 100 mg·L -1 phloroglucinol (PG). The accumulation of the taxifolin in elongation shoots and lignified elongation shoots have greatly improved along with the development process, were 28.6 µg·g -1, and 53 µg·g -1 respectively. The content of the taxifolin in callus was 1.99-5.26 µg·g -1, adventitious shoots were 4.8 µg·g -1, and adventitious roots were 2.86 µg·g -1. We report an efficient organogenesis and taxifolin production protocol in larch for the first time.

Conifer Biotechnology: An Overview

The peculiar characteristics of conifers determine the difficulty of their study and their great importance from various points of view. However, their study faces numerous important scientific, methodological, cultural, economic, social, and legal challenges. This paper presents an approach to several of those challenges and proposes a multidisciplinary scientific perspective that leads to a holistic understanding of conifers from the perspective of the latest technical, computer, and scientific advances. This review highlights the deep connection that all scientific contributions to conifers can have in each other as fully interrelated communicating vessels.