The capability of regenerative endodontics to promote the complete root formation in immature permanent teeth with different initial pre-operative conditions

OBJECTIVES

To describe the potential possibility of complete root formation after regenerative endodontic procedures (REPs) in immature permanent teeth with different initial pre-operative conditions.

MATERIALS AND METHODS

Children who underwent REPs in the Department of Pediatric Dentistry, Peking University School and Hospital of Stomatology, Beijing, China, from January 2013 to December 2022 were enrolled. Whether the tooth achieved complete root formation was determined using post-operative periapical radiography. The potential possibility of complete root formation after REPs in immature permanent teeth with different initial conditions is discussed.

RESULTS

A total of 428 teeth from 401 patients were included, of which 258 (60.2%) achieved complete root formation. In cases that achieved complete root formation, the most serious type of trauma was avulsion, the teeth with the worst initial root development were less than one-third of the development (stages 6-7), and the longest duration of the presence of apical lesions in the tooth before the first visit was more than 180 days. There is a significant difference in the root formation of teeth with different initial developmental stages and diagnoses.

CONCLUSIONS

The active period of continued root formation was 5-21 months post-operatively. The higher the initial stage of root development and the shorter the duration of the presence of apical lesions in the tooth before the first visit, the greater the possibility of root formation. However, complete root formation may still be expected after REPs in severely injured immature permanent teeth and teeth with poor initial pre-operative root development conditions (less than stage 7) at the first visit. This is also true for teeth with long-term and large-scale apical lesions.

SlGH3.15, a member of the GH3 gene family, regulates lateral root development and gravitropism response by modulating auxin homeostasis in tomato

Multiple Gretchen Hagen 3 (GH3) genes have been implicated in a range of processes in plant growth and development through their roles in maintaining hormonal homeostasis. However, there has only been limited study on the functions of GH3 genes in tomato (Solanum lycopersicum). In this work, we investigated the important function of SlGH3.15, a member of the GH3 gene family in tomato. Overexpression of SlGH3.15 led to severe dwarfism in both the above- and below-ground sections of the plant, accompanied by a substantial decrease in free IAA content and reduction in the expression of SlGH3.9, a paralog of SlGH3.15. Exogenous supply of IAA negatively affected the elongation of the primary root and partially restored the gravitropism defects in SlGH3.15-overexpression lines. While no phenotypic change was observed in the SlGH3.15 RNAi lines, double knockout lines of SlGH3.15 and SlGH3.9 were less sensitive to treatments with the auxin polar transport inhibitor. Overall, these findings revealed important roles of SlGH3.15 in IAA homeostasis and as a negative regulator of free IAA accumulation and lateral root formation in tomato.

Genome-wide identification, bioinformatics and expression analysis of HD-Zip gene family in peach

BACKGROUND

HD-Zips (Homeodomain-Leucine Zippers) are a class of plant-specific transcription factors that play multiple roles in plant growth and development. Although some functions of HD-Zip transcription factor have been reported in several plants, it has not been comprehensively studied in peach, especially during adventitious root formation of peach cuttings.

RESULTS

In this study, 23 HD-Zip genes distributed on 6 chromosomes were identified from the peach (Prunus persica) genome, and named PpHDZ01-23 according to their positions on the chromosomes. These 23 PpHDZ transcription factors all contained a homeomorphism box domain and a leucine zipper domain, were divided into 4 subfamilies(I-IV) according to the evolutionary analysis, and their promoters contained many different cis-acting elements. Spatio-temporal expression pattern showed that these genes were expressed in many tissues with different levels, and they had distinct expression pattern during adventitious root formation and development.

CONCLUSION

Our results showed the roles of PpHDZs on root formation, which is helpful to better understand the classification and function of peach HD-Zip genes.

Auxin efflux carrier ZmPIN1a modulates auxin reallocation involved in nitrate-mediated root formation

BACKGROUND

Auxin plays a crucial role in nitrate (NO₃^-)-mediated root architecture, and it is still unclear that if NO₃^- supply modulates auxin reallocation for regulating root formation in maize (Zea mays L.). This study was conducted to investigate the role of auxin efflux carrier ZmPIN1a in the root formation in response to NO₃^- supply.

RESULTS

Low NO₃^- (LN) promoted primary root (PR) elongation, while repressed the development of lateral root primordia (LRP) and total root length. LN modulated auxin levels and polar transport and regulated the expression of auxin-responsive and -signaling genes in roots. Moreover, LN up-regulated the expression level of ZmPIN1a, and overexpression of ZmPIN1a enhanced IAA efflux and accumulation in PR tip, while repressed IAA accumulation in LRP initiation zone, which consequently induced LN-mediated PR elongation and LR inhibition. The inhibition rate of PR length, LRP density and number of ZmPIN1a-OE plants was higher than that of wild-type plants after auxin transport inhibitor NPA treatment under NN and LN conditions, and the degree of inhibition of root growth in ZmPIN1a-OE plants was more obvious under LN condition.

CONCLUSION

These findings suggest that ZmPIN1a was involved in modulating auxin levels and transport to alter NO₃^--mediated root formation in maize.

Eruption pattern of the maxillary canines: features indicating treatment needs as seen in PTG at the late mixed stage-Part II

Aim

To describe features of maxillary permanent canines in the late mixed stage as seen in panoramic radiograph (PTG) that later needed treatment to erupt into the oral cavity and to compare them with naturally erupted canines.

Methods

The cross-sectional part of this retrospective register-based study consisted of 1454 PTGs of children (mean age 9.3 years) living in Eastern Finland, while the longitudinal part involved patient data on 184 treated maxillary canines. The variables examined were treatment needs, overlapping and inclination of the maxillary canines, the development stage of the canines and lateral incisors and dental age.

Results

Only 11.6% of the maxillary canines needed treatment, including interceptive procedures. The treated canines significantly more often had overlapping (p < 0.001), larger inclination (p = 0.001) and incomplete lateral incisors (p = 0.002) than did the naturally erupted canines. The children treated significantly more often had a delayed dental age (p = 0.035). Clear overlapping was closely associated with all treatment modalities, whereas some overlapping and a large inclination angle (≥ 25°) were associated especially in cases of late treatment. An incomplete lateral incisor and delayed dental age were associated with treatment.

Conclusion

An association with treatment needs was found especially in the case of overlapping and a large inclination angle of the maxillary canine a couple of years before eruption into the oral cavity. These features can be early signs and indications for instant or later treatment of a maxillary canine and underline the importance of monitoring space conditions and erupting canines.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40368-022-00719-5.

Differential expression pattern of novel MADS-box genes in early root formation and differentiation of sweet potato

MADS-box genes are important transcription factors affecting overall development, but their role in sweet potato [Ipomoea batatas (L.) Lam.] has not been fully studied. This study isolated six novel MADS-box genes (IbSOC1, IbFUL1, IbAGL6, IbSVP1, IbSVP2, and IbSVP3) from sweet potato [Ipomoea batatas (L.) Lam. cv. Annouimo] during the early root differentiation stage using the de novo transcriptome assembly sequencing method. At the early root differentiation (between 0 and 3 days after transplanting), the IbSOC1, IbFUL1, and IbSVP2 genes decreased rapidly, whereas the IbSVP3 gene decreased gradually. In the early stages of root formation (0-30 days), the levels of IbSVP1 and IbSVP3 expression were steady, but the levels of IbSOC1 expression decreased gradually. The expression of six novel genes was also conducted in the tuberous root formation stage (30-90 days), and the IbSVP3 gene increased significantly according to the formation of the tuberous root. Six novel MADS-box genes that were believed to influence the entire root formation of sweet potato were isolated from the sweet potato. This study provides a genetic basis for further research on sweet potato root formation and development.

Eruption pattern of the maxillary canines: features of natural eruption seen in PTG at the late mixed stage-Part I

Aim

To describe the variation of eruption pattern of maxillary canines in the late mixed stage of dentition seen in PTG when eruption was later natural.

Methods

Material for this longitudinal and retrospective register-based study consisted of 1454 PTGs of children living in Eastern Finland (mean age 9.3 years, SD 0.6). Natural eruption of a canine consisted of 744 PTGs (336 girls and 408 boys) including 1488 maxillary canines. The variables examined were treatment/natural eruption, overlapping, inclination, dental age, developmental stage of the canine and lateral incisor.

Results

Only 2.0% of maxillary canines had clear overlapping and 56.2% no overlapping was detected at the age of 8.5–10.5 years. Large inclination angle (≥ 25°) was found for 5.5% of examined canines. Overlapping of canine with lateral incisor root decreased as the development of canine root exceeded 1/3. Larger inclinations occurred at earlier stages but decreased significantly as the root developed from 1/3 to 1/2. Mean inclination was significantly larger at children with normal dental age and/or incomplete lateral incisors when overlapping occurred. Regardless overlapping mean inclination was larger if dental age was delayed and/or lateral incisors incomplete.

Conclusion

Some overlapping and larger inclination in maxillary canine are features of normal eruption pattern at an earlier stage of canine development and while lateral incisor is incomplete in PTG (8.5–10.5 years). In addition to the overlapping and inclination, stages of canine and lateral incisor root as well as dental age should be observed radiologically when evaluating erupting maxillary canine in children of this age.

Zygotic Embryogenesis in Flowering Plants

In the context of plant regeneration, in vitro systems to produce embryos are frequently used. In many of these protocols, nonzygotic embryos are initiated that will produce shoot-like structures but may lack a primary root. By increasing the auxin-to-cytokinin ratio in the growth medium, roots are then regenerated in a second step. Therefore, in vitro systems might not or only partially execute a similar developmental program as employed during zygotic embryogenesis. There are, however, in vitro systems that can remarkably mimic zygotic embryogenesis such as Brassica microspore-derived embryos. In this case, the patterning process of these haploid embryos closely follows zygotic embryogenesis and all fundamental tissue types are generated in a rather similar manner. In this review, we discuss the most fundamental molecular events during early zygotic embryogenesis and hope that this brief summary can serve as a reference for studying and developing in vitro embryogenesis systems in the context of doubled haploid production.

Functional genomics by integrated analysis of transcriptome of sweet potato (Ipomoea batatas (L.) Lam.) during root formation

BACKGROUND

Sweet potato is easily propagated by cuttings. But the molecular biological mechanism of adventitious root formation are not yet clear.

OBJECTIVE

To understand the molecular mechanisms of adventitious root formation from stem cuttings in sweet potato.

METHODS

RNA-seq analysis was performed using un-rooted stem (0 day) and rooted stem (3 days). Gene Ontology (GO) enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, comparison with Arabidopsis transcription factors (TFs) of DEGs were conducted to investigate the characteristics of genes and TFs involved in root formation. In addition, qRT-PCR analysis using roots at 0, 3, 6, 9, and 12 days after planting was performed to confirm RNA-seq reliability and related genes expression.

RESULTS

42,459 representative transcripts and 2092 DEGs were obtained through the RNA-seq analysis. The DEGs indicated the GO terms related to the single-organism metabolic process and cell periphery, and involved in the biosynthesis of secondary metabolites, and phenylpropanoid biosynthesis in KEGG pathways. The comparison with Arabidopsis thaliana TF database showed that 3 TFs (WRKY, NAC, bHLH) involved in root formation of sweet potato. qRT-PCR analysis, which was conducted to confirm the reliability of RNA-seq analysis, indicated that some metabolisms including oxidative stress and wounding, transport, hormone may be involved in adventitious root formation.

CONCLUSIONS

The detected genes related to secondary metabolism, some hormone (auxin, gibberellin), transports, etc. and 3 TFs (WRKY, NAC, bHLH) may have functions in adventitious roots formation. This results provide valuable resources for future research on the adventitious root formation of sweet potato.

mairei Cultivars

MicroRNAs (miRNAs) have been shown to play key roles in the regulation of plant growth and development by modifying the expression of their target genes. However, the influence of miRNAs on root formation and development in woody plants, such as Taxus chinensis, remains largely unknown. In the current study, we explored the phytohormone-response and nutrition-response miRNA expression profiles during T. chinensis rooting by quantitative real-time PCR (qPCR). We identified six phytohormone-response miRNAs, namely, miR164a, miR165, miR167a, miR171b, miR319, and miR391, and eight nutrition-response miRNAs, namely, miR169b, miR395a, miR399c, miR408, miR826, miR827, miR857, and miR2111a, that were differentially expressed at different rooting phases of T. chinensis. Using northern blot analysis of the putative target genes of these miRNAs, we detected the relative gene expression changes of the target genes. Taken together, our results suggest that miRNAs are involved in root formation of T. chinensis and that miRNAs may play important regulatory roles in primary root, crown root, and root hair formation by targeting phytohormone and/or nutrition response genes in T. chinensis. For the first time, these results expand our understanding of the molecular mechanisms of plant root formation and development in a conifer species.

The Solanum lycopersicum auxin response factor SlARF2 participates in regulating lateral root formation and flower organ senescence

ARF2 as apleiotropic developmental regulator has been reported in Arabidopsis thaliana and tomato (Solanum lycopersicum). The present study showed SlARF2 transcripts in all tomato plant tissues but with higher accumulation in flowers. During bud-anthesis stages, SlARF2 transcripts showed a dynamic expression pattern in sepal, stamen, ovary and petal. Hormone treatment analysis suggested that SlARF2 transcript accumulation was positively regulated by auxin and gibberellic acid, and negatively regulated by ethylene in tomato seedlings. Phenotypes and molecular analyses of SlARF2-upregulated transgenic tomato indicated that SlARF2 regulated tomato lateral root formation and flower organ senescence may be partially mediated by regulating the gene expression of auxin and ethylene response factors. The data enlarges the functional characterization of SlARF2 in tomato, and broadens our understanding of auxin signaling in regulating plant growth and development.

SlTIR1 is involved in crosstalk of phytohormones, regulates auxin-induced root growth and stimulates stenospermocarpic fruit formation in tomato

TIR1 and its homologs act as auxin receptors and play important roles in plant growth and development in Arabidopsis thaliana. An auxin receptor homolog Solanum lycopersicum TIR1 (SlTIR1) has been isolated from tomato cultivar Micro-Tom, and SlTIR1 over-expression results in parthenocarpic fruit formation. In this study, the promoter driving the β-glucuronidase (GUS) expression vector was constructed and stably transformed into Micro-Tom seedlings. The SlTIR1 promoter driving GUS expression accumulated predominantly in the leaf and vasculature in transgenic seedlings. Promoter analysis identified an auxin-response element (AuxRE) and two gibberellic acid (GA)-response elements in the SlTIR1 promoter. Quantitative PCR showed that SlTIR1 transcript level was down-regulated by naphthaleneacetic acid, ethephon and abscisic acid and up-regulated by GA. Furthermore, because of the lack of ability to form reproductive seeds in SlTIR1 over-expressing Micro-Tom, this limits further exploration of potential roles of SlTIR1 in auxin signaling. Here, an antisense vector and an over-expression vector of the SlTIR1 gene were stably transformed into Micro-Tom and Ailsa Craig tomato, respectively. Phenotypes and physiological analyses indicated that SlTIR1 regulated primary root growth and auxin-associated lateral root formation in Micro-Tom. Meanwhile, SlTIR1 also stimulated abnormal seed development, so-called stenospermocarpy, in Ailsa Craig. Transcript accumulations of auxin-signaling genes determined by quantitative PCR were consistent with the idea that SlTIR1 regulated plant growth and development, partially mediated by controlling the mRNA levels of auxin-signaling genes. Our work demonstrates that SlTIR1 regulated auxin-induced root growth and stimulated stenospermocarpic fruit formation. SlTIR1 may be a key mediator of the crosstalk among auxin and other hormones to co-regulate plant growth and development.

MicroRNAs, polyamines, and the activities antioxidant enzymes are associated with in vitro rooting in white pine (Pinus strobus L.)

Molecular mechanism of in vitro rooting in conifer is not fully understood. After establishment of a regeneration procedure in eastern white pine (Pinus strobus L.) using mature embryos as explants to induce shoot formation on medium containing 3 μM IAA, 6 μM BA and 6 μM TDZ and induce root formation on medium containing 0.001-0.05 μM IAA, 0.001-0.05 μM IBA, 0.001-0.05 μM TDZ, we have investigated the changes of polyamine content and the activities of antioxidant enzymes during in vitro rooting in P. strobus. Our results demonstrated that putrescine (Put), spermidine (Spd), and spermine (Spm) did not increase in P. strobus during the first week of rooting on medium supplemented with 0.01 μM indole-3-acetic acid (IAA), whereas the levels of Put, Spd, and Spm increased during the 1st-3rd week of culture on medium with IAA, and then decreased on medium with IAA. No such a change in Put, Spd, and Spm was observed on medium without IAA. Measurement of antioxidant enzyme activity demonstrated that the activities of polyphenol oxidase, catalase, and peroxidase slightly increased in the first week of culture and reached to the highest peak in the 3rd-5th week of culture. Quantitative RT-PCR results indicated that miR160 was increased on the 7th day, miR162, miR397, and miR408 was increased from the 21th to 35th day, miR857 was increased on the 35th day, and miR827 was increased on the 49th day. These results demonstrated that enhanced polyamine biosynthesis, antioxidant enzyme activity, and microRNAs are correlated with the root induction and formation in P. strobus.

Regulatory mechanisms of Hertwig׳s epithelial root sheath formation and anomaly correlated with root length

Teeth are composed of two domains, the enamel-covered crown and cementum-covered root. The mechanism for determining the transition from crown to root is important for understanding root anomaly diseases. Hertwig׳s epithelial root sheath (HERS) is derived from the dental epithelium and is known to drive the growth of root dentin and periodontal tissue. Some clinical cases of hypoplastic tooth root are caused by the cessation of HERS development. Understanding the mechanisms of HERS development will contribute to the study of the disease and dental regenerative medicine. However, the developmental biology of tooth root formation has not been fully studied, particularly regarding HERS formation. Here, we describe the mechanisms of HERS formation on the basis of analysis of cell dynamics using imaging and summarize how the growth factor and its receptor regulate cell behavior of the dental epithelium.