Eucalyptus cloeziana is an important, fast-growing, precious timber species in southern China, with tissue culture being the primary method for its propagation. However, the declining proliferation coefficient of adventitious shoots with multi-generation culture is a major constraint on its rapid propagation. This study aims to address this issue through the selection of suitable explants and optimizing the plant growth regulators’ formulation during the process of shoot proliferation. In this study, we cut shoots from the 21st generation of the tissue-cultured seedlings of ‘Chuanlinzhen 7523’ into apical, middle, and basal sections, and we measured their content of endogenous hormones. The proliferation coefficient (PC) and growth coefficient (GC) of explants under different concentrations of plant growth regulators were analyzed and ranked using the PCA method. The results indicated that the shoot basal sections were the best for proliferation when treated with 0.40 mg/L BAP (6-benzylaminopurine), 0.20 mg/L NAA (naphthaleneacetic acid), and 0.20 mg/L TDZ (thidiazuron), yielding a PC of 4.7 and a GC of 4.1. These basal sections ranked first with a rooting rate of up to 80%. When the rooted plantlets were acclimatized in the nursery, a survival rate of 100% was achieved. This protocol—from proliferation to acclimation—effectively improves the propagation efficiency of E. cloeziana ‘Chuanlinzhen 7523’ after multi-generation propagation.
Abstract Ethylene response factors (ERF) are members of the APETALA2/ERF transcription factor family, and they play an important role in plant growth, development, and response to various environmental stresses. In the present study, an ERF transcription factor HcERF4 was isolated and characterized from kenaf. The protein encoded by the HcERF4 has 233 amino acid residues with a theoretical isoelectric point of 8.89 and a predicted molecular weight of 25.53 kDa. HcERF4 had an over than 86.97% identity to HsERF4 (XP_039019980.1), and shared a closest phylogenetic relationship with Hibiscus syriacus . Subcellular localization analysis shows that HcERF4 is located in the nucleus. Transactivation assays in yeast demonstrated that HcERF4 functions as a transcriptional activator. The expression of HcERF4 was enriched in leaf and root, and can be induced by salt or drought treatments in kenaf. The VIGS-silenced HcERF4 plant showed significantly reduced plant height, stem diameter, fresh weight, and relative water content (RWC) compared with wild type plants under salt or drought stress condition; In addition, the contents of MDA, O 2 − , H 2 O 2 , and free proline is significantly increased, and the activities of SOD and CAT are significantly reduced. The DAB/NBT staining results showed that the H 2 O 2 and O 2 − contents in HcERF4 -silenced plants were consistent with the determination. Based on these results, it is proposed that HcERF4 plays an important role in regulating salt and drought stress in kenaf.
Abstract Background Soil salt alkalization is one major abiotic factor reducing the productivity of crops worldwide, including rapeseed ( Brassica napus L.), an indispensable oil crop and vegetable. The mechanism studies of alkali-salt-tolerance are helpful for the breeding of high resistant varieties and the expansion of the planting area. However, the study of the alkaline salt tolerance mechanism in rapeseed is limited. This study aimed to identify candidate genes related to the regulation of alkali salt tolerance in B. napus . Results In the current study, B. napus line 2205 exhibited stronger tolerance to alkaline salt than B. napus line 1423. In line 2205, the lesser plasma membrane damage index, the accumulated osmotic adjustment substances, and higher antioxidant enzyme activities were contributed to alkaline tolerance. Ultrastructure observation found that the mesophyll cells of line 2205 had higher integrity compared with line 1423, further confirming that line 2205 suffered a lesser injury under alkali-salt stress. Transcriptome analysis showed that more genes responded to alkaline salt in line 2205, and the expressions of respective specific response genes were different in these two cultivars. The expression level of the line-1423-specific-response genes was lower in line 2205, which were primarily annotated to the cytosol, spliceosome, and ubiquitin-mediated proteolysis, whereas most of the specific response genes in line 2205 had a higher expression, which were mainly enriched in carbohydrate metabolism, photosynthetic processes, ROS regulating, and response to salt stress. It can be seen that the tolerance to alkaline salt is attributed to the high expression of some genes in these pathways. Based on these results, twelve cross-differentially expressed genes, including BnMDH2 , BnGAPCs , BnACO1 , BnGOXs, and BnGGTAs , were proposed as candidate genes for regulating alkali-salt tolerance in rapeseed. Conclusions The present study demonstrates that tolerant rapeseed exhibits superior physiological indicators and actively mobilizes genes involved in energy metabolism and ROS-related pathways to resist undesirable adverse signals from alkaline salts. The candidate genes provide reliable clues for further analysis of the resistance mechanism of rapeseed.
In this report, we compared transcriptomic differences between a synthetic Populus section Tacamahaca triploid driven by second-division restitution and its parents using a high-throughput RNA-seq method. A total of 4,080 genes were differentially expressed between the high-growth vigor allotriploids (SDR-H) and their parents, and 719 genes were non-additively expressed in SDR-H. Differences in gene expression between the allotriploid and male parent were more significant than those between the allotriploid and female parent, which may be caused by maternal effects. We observed 3,559 differentially expressed genes (DEGs) between the SDR-H and male parent. Notably, the genes were mainly involved in metabolic process, cell proliferation, DNA methylation, cell division, and meristem and developmental growth. Among the 1,056 DEGs between SDR-H and female parent, many genes were associated with metabolic process and carbon utilization. In addition, 1,789 DEGs between high- and low-growth vigor allotriploid were mainly associated with metabolic process, auxin poplar transport, and regulation of meristem growth. Our results indicated that the higher poplar ploidy level can generate extensive transcriptomic diversity compared with its parents. Overall, these results increased our understanding of the driving force for phenotypic variation and adaptation in allopolyploids driven by second-division restitution.
Histocytological studies were conducted on primary, secondary, and malformed embryos produced during somatic embryogenesis of Cinnamomum camphora L. to better understand its development. Exploring its callus types and structures provided a theoretical basis for clarifying the mechanism of somatic embryogenesis, which may shed light on the mechanism of zygotic embryogenesis. We used immature zygotic embryos as explants to induce somatic embryos, forming many embryogenic calli that differentiated into mature somatic embryos. Our results showed that somatic embryogenesis of C. camphora was similar to that of zygotic embryos. We have been dedifferentiated four types of callus. Compared with non-embryogenic cells, embryogenic cells had a closer arrangement, larger nucleus, thicker cytoplasm, more starch granules and easier to stain into black. Somatic embryogenesis had two pathways: direct (predominate) and indirect (rare). Embryogenic cells of C. camphora could have either an internal or external origin, the latter being primary, for which occurrence sites include epidermis and near-epidermis (little internally). Mostly arising from single cells, C. camphora follows two developmental pathways: single-cell equal as opposed to unequal, wherein both divide to form multi-cell proembryos. However, multicellular origins can occasionally occur and feature physiological isolation during somatic embryo development. This development has four embryo stages: globular, heart-shaped, torpedo, and cotyledon, with procambium cells apparent in globular embryos and late cotyledons forming “Y-shaped” vascular bundles. Secondary embryos were present in all stages, directly occurring on primary embryo’s germ and radicle end surfaces. We conclude that secondary and primary embryos of C. camphora undergo similar developmental processes. At the same time, conjoined cotyledon embryos and morphological abnormal embryos were found, with an internal origin more likely to generate abnormal embryos.
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In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 4, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue.
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α-Linolenic acid (ALA) is an important nutrient component in rapeseed oil, and rapeseed breeders want to either restrain or enhance the function of fatty acid desaturases (FADs) in the ALA biosynthesis pathway. To determine the reason for the upregulation of rapeseed BnFAD genes in two high-ALA accessions, R8Q10 and YH25005, we compared their transcriptome profiles in the seed at 24 days after pollination (DAP) with those of two low-ALA lines, A28 and SW. The expression levels of twenty-eight important genes in the seed samples at 20, 27, and 34 DAP were also investigated using an RT-qPCR. The expression levels of genes involved in flavonoid and proanthocyanidin synthesis, including BnCHS, BnCHI, BnDFR, BnFLS1, BnLDOX, BnBAN, BnTT10, and BnTT12 and genes encoding the transcription factors BnTT1, BnTT2, BnTT8, and BnTT16 were lower in R8Q10 and YH25005 than in A28 and SW. The expression levels of genes encoding master transcription factors in embryo development, such as BnLEC1, BnABI3, BnFUS3, BnL1L, BnAREB3, and BnbZIP67, were elevated significantly in the two high-ALA accessions. Combined with previous results in the Arabidopsis and rapeseed literature, we speculated that the yellow-seededness genes could elevate the activity of BnLEC1, BnABI3, BnFUS3, and BnbZIP67, etc., by reducing the expression levels of several transparent testa homologs, resulting in BnFAD3 and BnFAD7 upregulation and the acceleration of ALA synthesis. Yellow-seededness is a favorable factor to promote ALA synthesis in the two high-ALA accessions with the yellow-seeded trait. These findings provide initial insights into the transcriptomic differences between high-/low-ALA germplasms and a theoretic basis for seed quality breeding.
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