Adventitious Root Development Research Articles

Unraveling Key Factors for Hypoxia Tolerance in Contrasting Varieties of Cotton Rose by Comparative Morpho-physiological and Transcriptome Analysis.

The cotton rose (Hibiscus mutabilis) is a plant species commonly found in tropical and subtropical regions. It is remarkably resilient to waterlogging stress; however, the underlying mechanism behind this trait is yet unknown. This study used hypoxia-tolerant "Danbanhong" (DBH) and more hypoxia-sensitive "Yurui" (YR) genotypes and compared their morpho-physiological and transcriptional responses to hypoxic conditions. Notably, DBH had a higher number of adventitious roots (20.3) compared to YR (10.0), with longer adventitious roots in DBH (18.3 cm) than in YR (11.2 cm). Furthermore, the formation of aerenchyma was 3-fold greater in DBH compared to YR. Transcriptomic analysis revealed that DBH had more rapid transcriptional responses to hypoxia than YR. Identification of a greater number of differentially expressed genes (DEGs) for aerenchyma, adventitious root formation and development, and energy metabolism in DBH supported that DBH had better morphological and transcriptional adaptation than YR. DEG functional enrichment analysis indicated the involvement of variety-specific biological processes in adaption to hypoxia. Plant hormone signaling transduction, MAPK signaling pathway and carbon metabolism played more pronounced roles in DBH, whereas the ribosome genes were specifically induced in YR. These results show that effective multilevel coordination of adventitious root development and aerenchyma, in conjunction with plant hormone signaling and carbon metabolism, is required for increased hypoxia tolerance. This study provides new insights into the characterization of morpho-physiological and transcriptional responses to hypoxia in H. mutabilis, shedding light on the molecular mechanisms of its adaptation to hypoxic environments.

Variation in Root System Architecture Response to Arsenic during Establishment and Onset of Storage Root Formation in Two Sweetpotato (Ipomoea batatas L.) Cultivars

The primary objective of this work was to generate species-specific information about root architectural adaptations to simulated natural levels of arsenic (As) during the establishment phase and onset of storage root formation in sweetpotato. Cultivars Bayou Belle and Beauregard were grown on sand substrate and provided with 0.5X Hoagland’s nutrient solution with varying levels of As (0, 5, 10, or 15 mg⋅L−1). During the first experiment, entire root systems were sampled at 5, 10, and 15 days, corresponding to key adventitious root developmental stages. Compared with the untreated controls at 15 days, ‘Bayou Belle’ and ‘Beauregard’ provided with 15 mg⋅L−1 As showed respective increases in the following root architectural attributes: 168% and 130% in main root length; 168% and 98% in lateral root length; and 140% and 50% in lateral root density. A second experiment was performed to produce storage root samples at 50 days. Storage root length, width, and length/width ratio did not vary with As levels. The accumulation of As in storage roots increased with increasing As levels. The results support the hypothesis that natural As levels stimulate adventitious root development in sweetpotato in a cultivar-dependent manner. The observations are consistent with findings of other species that show similar growth stimulation at low As levels. This is the first report of sweetpotato root system architecture responses to experimental levels of As that are known to be present in agricultural soils. Standardization of experimental procedures and understanding of root system adaptations to natural levels of As could lead to a more systematic exploitation of genome-wide techniques and characterization of the molecular basis of reduced As uptake in plants.

Identification and functional analysis of a CbSHR homolog in controlling adventitious root development in Catalpa bungei

Identification and functional analysis of a CbSHR homolog in controlling adventitious root development in Catalpa bungei

Transcriptome analysis of waterlogging-induced adventitious root and control taproot of Mentha arvensis.

The present study reports differentially expressed transcripts in the waterlogging-induced adventitious root (AR) of Mentha arvensis; the identified transcripts will help to understand AR development and improve waterlogging stress response. Waterlogging notably hampers plant growth in areas facing waterlogged soil conditions. In our previous findings, Mentha arvensis was shown to adapt better in waterlogging conditions by initiating the early onset of adventitious root development. In the present study, we compared the transcriptome analysis of adventitious root induced after the waterlogging treatment with the control taproot. The biochemical parameters of total carbohydrate, total protein content, nitric oxide (NO) scavenging activity and antioxidant enzymes, such as catalase activity (CAT) and superoxide dismutase (SOD) activity, were enhanced in the adventitious root compared with control taproot. Analysis of differentially expressed genes (DEGs) in adventitious root compared with the control taproot were grouped into four functional categories, i.e., carbohydrate metabolism, antioxidant activity, hormonal regulation, and transcription factors that could be majorly involved in the development of adventitious roots. Differential expression of the upregulated and uniquely expressing thirty-five transcripts in adventitious roots was validated using qRT-PCR. This study has generated the resource of differentially and uniquely expressing transcripts in the waterlogging-induced adventitious roots. Further functional characterization of these transcripts will be helpful to understand the development of adventitious roots, leading to the resistance towards waterlogging stress in Mentha arvensis.

Abiotic Stress Responses in Woody Plants: Morphological, Physiological, and Anatomical Features

Abiotic stressors may have intricate and varied impacts on the growth and development of forest trees. This article provides a comprehensive summary of the effects of abiotic stressors, such as flood, drought, severe temperature, salt, heavy metal, combination stresses, and microplastics, on the morphological, physiological, and anatomical features of woody plants. The focus is particularly on evaluating these effects from the viewpoint of the xylem. During abiotic stress, the ability of xylem to transport water declines, which is linked to the control of leaf stomata and the suppression of aquaporin (AQP) function. Concurrently, woody plants maintain control over the dimensions and structure of their roots and leaves in order to achieve a harmonious equilibrium between water intake and evaporation. The anatomical characteristics are modified as well, including increased density of leaf stomata, smaller conduits, and thicker cell walls. Furthermore, various types of stressors elicit distinct responses in plants. For instance, flooding leads to the development of adventitious roots and aeration tissues, while forest fires cause irreparable damage to the xylem. Low temperatures result in tissue freezing, salt stress hinders ion absorption, and exposure to heavy metals induces biological toxicity. Woody plants' growth may be periodically enhanced in conditions of drought, floods, and exposure to heavy metals. The impact of combined stress on the physiological, morphological, and anatomical characteristics of woody plants is not only cumulative. The underlying mechanism behind this phenomenon requires additional investigation, particularly in natural or near-natural environments.

Characterization and genetic differences analysis in adventitious roots development of 38 Populus germplasm resources.

To select poplar clones with excellent adventitious roots development (ARD) and deepen the understanding of its molecular mechanism, a comprehensive evaluation was conducted on 38 Populus germplasm resources with cuttings cultured in the greenhouse. Genetic differences between poplar clones with good ARD and with poor ARD were explored from the perspectives of genomics and transcriptomics. By cluster analysis of the seven adventitious roots (AR) traits, the materials were classified into three clusters, of which cluster I indicated excellent AR developmental capability and promising breeding potential, especially P.×canadensis 'Guariento', P. 'jingtong1', P. deltoides 'Zhongcheng5', P. deltoides 'Zhongcheng2'. At the genomic level, the cross-population composite likelihood ratio (XP-CLR) analysis identified 1944 positive selection regions related to ARD, and variation detection analysis identified 3426 specific SNPs and 687 specific Indels in the clones with good ARD, 3212 specific SNPs and 583 specific Indels in the clones with poor ARD, respectively. Through XP-CLR, variation detection, and weighted gene co-expression network analysis based on transcriptome data, eight major putative genes associated with poplar ARD were primary identified, and a co-expression network of eight genes was constructed, it was discovered that CSD1 and WRKY6 may be important in the ARD. Subsequently, we confirmed that SWEET17 had a non-synonymous mutation at the site of 928,404 in the clones with poor ARD, resulting in an alteration of the amino acid. After exploring phenotypic differences and the genetic variation of adventitious roots development in different poplar clones, this study provides valuable reference information for future poplar breeding and genetic improvement.

Transcription Factor MdPLT1 Involved Adventitious Root Initiation in Apple Rootstocks

The induction of adventitious roots is a key factor restricting the vegetative propagation of apple dwarf rootstocks. PLETHORA (PLT) transcription factors are involved in the regulation of plant stem cell niche and adventitious root development. In this study, we identified the PLT1 gene in apples by bioinformatics and analyzed its evolutionary relationship. The MdPLT1 gene was cloned from M9-T337 to verify its subcellular localization and analyze its function in transgenic tobacco. The MdPLT1 protein contained two conserved AP2 domains which may be similar to those of poplar the PtrPLT2a and PtrPLT2b with 85% support. The CDS sequence of the MdPLT1 gene was 1638 bp, encoding 545 amino acids. The transcription factor MdPLT1 was localized in the nucleus. The number of adventitious roots of tobacco plants overexpressing MdPLT1 significantly increased. In the adventitious roots of MdPLT1-overexpressed plants, the expression levels of genes related to the NtPINs family and the NtYUCCAs family were significantly increased. The results showed that MdPLT1 positively regulated adventitious root formation. This study provided a theoretical basis for the establishment of the fast vegetative propagation of apple dwarf rootstocks.

Morpho-physiological and phytohormonal changes during the induction of adventitious root development stimulated by exogenous IBA application in Magnolia biondii Pamp

Abstract Magnolia biondii Pamp is an important ornamental tree species widely grown and used as a rootstock in the propagation of different Magnolia varieties. In the current studies, anatomical, physiological and endogenous hormones were studied to check the effect of IBA 750 mg/L on the adventitious rooting and to provide theoretical and technical support for the propagation of Magnolia biondii Pamp through stem cuttings. Two thousand stem cuttings were prepared and divided into two groups i.e., IBA treated cuttings and water control. For the evaluation of antioxidant enzyme activities, and endogenous hormones levels, samples were collected on the day of planting and each 5th day and further steps were carried out in the laboratory according to the protocols and proper precautions. For the anatomical observations, samples were collected on the 13th, 15th, and 17th day for IBA treated cuttings while 21st, 23rd, and 25th day for control. Collected samples were preserved in the FAA solution and further observations were carried out in the laboratory. Anatomical observations showed that it took 13 days for the differentiation of root primordia to the appearance of young adventitious roots in IBA treated cuttings, while it took 21 days to develop primordia in the control. Antioxidant enzyme activities involved in ROS were significantly higher in the IBA treated cuttings compared to control. POD showed a peak on the 13th day before the emergence of roots in IBA treated cuttings while it showed a peak on the 21st day in the control. PPO showed a peak on the 21st day in the IBA treated cuttings while it showed a peak on the 29th day in the control. SOD showed a peak on the 17th day in IBA treated cuttings, while it showed a peak on the 25th day in the control. Exogenous application of IBA enhanced the endogenous IAA and GA3 levels compared to CK, while it reduced the levels of ABA continuously at the time of rooting and then increased gradually. Inclusively, our study suggests that IBA 750 mg/L is efficient for the rooting of Magnolia biondii Pamp cuttings, as it enhanced the process of antioxidant enzyme activities, endogenous hormones levels and reduced the time of root formation which is evident from the anatomical observations.

Global Analysis of the WOX Transcription Factor Family in Akebia trifoliata.

Akebia trifoliata is an economically important, self-incompatible fruit tree in the Lardizabalaceae family. Asexual propagation is the main strategy used to maintain excellent agronomic traits. However, the generation of adventitious roots during asexual propagation is very difficult. To study the important role of the WUSCHEL-related homeobox (WOX) transcription factor in adventitious root growth and development, we characterized this transcription factor family in the whole genome of A. trifoliata. A total of 10 AktWOXs were identified, with the following characteristics: length (657~11,328 bp), exon number (2~5), isoelectric point (5.65~9.03), amino acid number (176~361 AA) and molecular weight (20.500~40.173 kDa), and their corresponding expression sequence could also be detectable in the public transcriptomic data for A. trifoliata fruit. A total of 10 AktWOXs were classified into modern (6), intermediate (2) and ancient clades (2) and all AktWOXs had undergone strong purifying selection during evolution. The expression profile of AktWOXs during A. trifoliata adventitious root formation indicated that AktWOXs play an important role in the regulation of adventitious root development. Overall, this is the first study to identify and characterize the WOX family in A. trifoliata and will be helpful for further research on A. trifoliata adventitious root formation.

Comprehensive Analysis of WUSCEL-Related Homeobox Gene Family in Ramie (Boehmeria nivea) Indicates Its Potential Role in Adventitious Root Development.

A WUSCHEL-related homeobox (WOX) gene family has been implicated in promoting vegetative organs to embryonic transition and maintaining plant embryonic stem cell identity. Using genome-wide analysis, we identified 17 candidates, WOX genes in ramie (Boehmeria nivea). The genes (BnWOX) showed highly conserved homeodomain regions typical of WOX. Based on phylogenetic analysis, they were classified into three distinct groups: modern, intermediate, and ancient clades. The genes displayed 65% and 35% collinearities with their Arabidopsis thaliana and Oryza sativa ortholog, respectively, and exhibited similar motifs, suggesting similar functions. Furthermore, four segmental duplications (BnWOX10/14, BnWOX13A/13B, BnWOX9A/9B, and BnWOX6A/Maker00021031) and a tandem-duplicated pair (BnWOX5/7) among the putative ramie WOX genes were obtained, suggesting that whole-genome duplication (WGD) played a role in WOX gene expansion. Expression profiling analysis of the genes in the bud, leaf, stem, and root of the stem cuttings revealed higher expression levels of BnWOX10 and BnWOX14 in the stem and root and lower in the leaf consistent with the qRT-PCR analysis, suggesting their direct roles in ramie root formation. Analysis of the rooting characteristics and expression in the stem cuttings of sixty-seven different ramie genetic resources showed a possible involvement of BnWOX14 in the adventitious rooting of ramie. Thus, this study provides valuable information on ramie WOX genes and lays the foundation for further research.

ARF4 acting upstream of LBD16 promotes adventitious root formation in peach

Although class A auxin response factors (ARFs) are known to regulate adventitious root (AR) development through the canonical SCFTIR1-Aux/IAA-ARF signaling pathway, the regulatory role of class B ARFs in AR development remains largely unclear. Therefore, this research focused on the role of class B ARF transcription factors in peach (Prunus persica ‘Shengli’) adventitious root formation. Here, we report the role of a class B ARF gene PpARF4 in adventitious root formation in peach. Comparative transcriptome and qRT-PCR analyses showed that the transcription of PpARF4 was significantly up-regulated in auxin-treated stem explants. Y2H assay showed that PpARF4 had no interaction with PpIAAs (AUXIN/INDOLE ACETIC ACIDs). PpARF4 could bind the promoters of lateral root development gene PpLBD16 and auxin transport gene PpPIN1 to activate their transcription. Ectopic overexpression of PpARF4 and PpLBD16 in Arabidopsis promoted AR development. Additionally, PpARF4 could act as a negative regulator of flavone synthesis and thus prevent the explants from browning. The results not only provide novel insights into the functions of ARFs in regulating plant growth and development, but will also be useful for fulfilling asexual propagation by stem cuttings in peach.

Effect of alternative rooting inducers on Umbu-cajazeira

The propagation by the sexual method of some species of the genus Spondias, such as the umbu-cajazeira, is practically unfeasible, due to the fact that its pit rarely contains seeds, making it necessary to propagate vegetatively by the cutting method. To enhance the rhizogenesis process, plant hormones are used, such as auxins, which results in the development of adventitious roots. In view of the above, the objective was to evaluate the effect of an alternative source of natural plant hormone on the rooting of tree cuttings Umbu-cajazeiraThe experiment was carried out in the fruit seedling nursery. The woody cuttings were removed from Umbu-cajazeira in vegetative rest. After collecting and preparing the cuttings, they were subjected to immersion in the solutions of AIB, ERT, ESL, AC and Water (evidence). After 90 days, the percentage of sprouted and rooted cuttings, number of leaves and shoots and roots, length and diameter of the largest shoot and largest root, dry mass of the root system and dry mass of shoots were evaluated. The data obtained were subjected to statistical analysis using the Tukey test at 5% probability. It was observed that the use of IBA provided 94% sprouting of the cuttings. The percentage of rooting of umbu-cajazeira cuttings was significant due to the use of alternative rooting inducers and indolebutyric acid, due to considerable amounts of auxins present in the extracts, inducing rhizogenesis in the cuttings. The AIB enhances the rooting and budding of umbu-cajazeira cuttings. The lentil extract is a natural plant hormone alternative for rooting umbu-cajazeira cuttings.

Melatonin-induced development of adventitious roots, biosynthesis of secondary cell products and greener synthesis of silver nanoparticles for biological activities using Indigofera heterantha

Indigofera heterantha is a medicinal shrub of the family Fabaceae that naturally produces pharmaceutically important polyphenolics and at the verge of extinction due to ruthless exploitation. The adventitious roots provide bases for the conservation of endangered plants by decreasing pressure on their wild populations and help in the large-scale production of pharmacologically important secondary metabolites. The main objective of the current study was to establish a feasible protocol for adventitious roots and to investigate the effect of melatonin on the biosynthesis of biomass, secondary cell products, and greener synthesis of silver nanoparticles (AgNPs) for various biological activities. Melatonin is an important growth promoter and plays a key role in plant defense that can be used as elicitors for large-scale production of secondary metabolites. Different concentrations of melatonin revealed that 1.5 mg l−1 melatonin was effective for the biosynthesis of maximum biomass during log phases of growth kinetics. The same melatonin concentration enhanced total phenolics content (TPC; 68.28 mg/g-DW), total flavonoids content (TFC; 24.34 mg/g-DW), total phenolics production (TPP; 153.63 g l−1), total flavonoids production (TFP; 54.80 g l−1), antioxidant activity and total secondary metabolites in adventitious roots. The melatonin-treated roots (300 mM) were able to produce maximum biogenic AgNPs, characterized by UV–vis spectroscopy (UV), scanning electron microscope (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD) and were used for various biological activities. These NPs displayed maximum antimicrobial activities and further revealed that AgNPs and aqueous root extract displayed higher cytotoxic activities. The protocol developed here provides an alternative strategy for germplasm conservation and melatonin proved to be one of the best elicitors for different activities and has the potential of scaling up by various pharmaceutical industrial applications.

Insight into regulation of adventitious root formation by arbuscular mycorrhizal fungus and exogenous auxin in tea plant (Camellia sinensis L.) cuttings.

Adventitious root (AR) development, affected by various biotic and abiotic factors, is the most important procedure in tea plant (Camellia sinensis L.) cutting propagation. Establishing symbiotic relationships with most terrestrial plants, AMF (Arbuscular mycorrhizal fungus) can mediate the AR formation of several herbaceous and woody plants in previous studies. In this paper, effects of combined application of AMF and exogenous auxin on AR formation of cuttings from different tea plant varieties ('Pingyangtezao', 'Longjing 43' and 'Longjingchangye') were studied. Then we also performed RNA-Seq analysis with 'Pingyangtezao' cuttings aiming to find the possible auxin-related pathway of AM fungal regulation on AR formation. To accurately uncover the regulatory mechanism of AMF on AR formation of tea cuttings, rooting process were separated into four stages (S0, non-rooting; S1, AR protrusion; S2, AR formation and S3, AR elongation) at the same sampling time. Results showed that IBA treatment increased the mycorrhizal colonization rate, especially in 'Pingyangtezao' variety (from 37.58% to 46.29%). Both inoculating AMF and addition of IBA promoted the AR formation, and rooting of different tea plant varieties showed different dependence on auxin. AMF could alleviate the effect of auxin-related inhibitors (2,3,5-triiodobenzoic acid, L-α-(Aminooxy)-β-phenylpropionic acid and α-(phenylethyl-2-oxo)-IAA) on rooting of tea cuttings, even though the colonization of AMF was hindered at various degrees. Transcriptomic analysis showed that different numbers of differentially expressed genes (DEGs) at various rooting stages of tea cuttings with the most at S2 stage (1360 DEGs), indicating the increasing regulation by AMF with the development of AR. Similar trend was found in auxin-related DEGs, and family genes of YUC, GH, PIN, LAX, SAUR, AUX, and ABP involved in the AM fungal regulation on AR formation of tea cuttings. Additionally, AMF strongly mediated auxin transport and signal transduction pathways in tea cuttings as showed by the results of correlation analysis. Overall, interaction of AMF and exogenous auxin in promoting rooting and the preliminary mechanism of AMF regulating AR formation of tea cuttings was deciphered in this paper, which may provide a basis for further deep mechanistic research and cutting propagation of tea production.

IBA and melatonin increase trigonelline and caffeine during the induction and initiation of adventitious roots in Coffea arabica L. cuttings

Caffeine and trigonelline are found in Coffea arabica, and show antioxidant roles and growth and development functions. However, there are no reports on trigonelline and caffeine in relation to coffee rooting. The aim was to evaluate the impact of application of indole-3-butyric acid (IBA) and melatonin on caffeine and trigonelline at different stages of adventitious rooting in cuttings. In addition, to study the correlation between these metabolites and H2O2, phenols, and antioxidant enzymes. Four treatments (Control, melatonin 21 µM (M21), melatonin 43 µM (M43), and IBA 7380 µM (IBA)) were used, with four replications. The growth and biochemical parameters of the antioxidant system were performed in induction, initiation, and extension rooting stages. Higher concentrations of trigonelline and caffeine quantified in the induction and initiation stages were positively correlated with higher percentage of rooted cuttings. Trigonelline and caffeine were positively correlated with H2O2 in all stages of development of adventitious roots. The correlations of trigoneline and caffeine with phenols and antioxidant enzymes reveal different profiles, depending on the phases. The results indicate that IBA and melatonin increase trigonelline and caffeine during the induction and initiation of adventitious roots in Coffea arabica cuttings, which is correlated with a higher percentage of rooted cuttings.

Effects of Plant Growth Promoting Rhizospheric Bacteria (PGPR) on Survival, Growth and Rooting Architecture of Eucalyptus Hybrid Clones

Clonal plantation involves the rooting of cuttings from superior genotypes selected for their hybrid vigor and desired qualities. However, the cuttings of some Eucalyptus species and their hybrid genotypes present difficulties in their rooting capacity. Applying PGPR to cutting growth medium as a root stimulating agent has not been extensively studied for Eucalyptus tree species. We aimed to assess the rooting capacity of cuttings taken from two poor-rooting Eucalyptus hybrid clones of E. grandis × E. nitens through the application of PGPR in nursery trials. Seven rhizospheric bacterial species that demonstrated the ability to produce indole-3-acetic acid and to solubilise phosphate were used to prepare two rhizospheric consortium inoculums in which Pseudomonas-Bacillus strains and non-Pseudomonas-Bacillus were grouped. Inoculums were tested for their rooting stimulating capacity on cuttings of the hybrids GN 018B and GN 010 and compared to the nursery standard indole-3-butyric acid. A total of 320 cuttings were treated. Both hybrid clones demonstrated significant (p < 0.0001) genotype differences for all three growth responses, i.e., total, root, and shoot length. Cuttings of both hybrids demonstrated high survival rates and rooting percentage. Although several rooting architectural configurations were prevalent, the Pseudomonas-Bacillus consortium promoted adventitious root development and fibrosity in GN 018B hybrids.

Callus Induction and Adventitious Root Regeneration of Cotyledon Explants in Peach Trees

Callus induction is a key step in establishing plant regeneration and genetic transformation. In this study, we present a comprehensive large-scale investigation of the callus induction rate (CIR) in peach trees, which revealed significant variability within the peach germplasm. Notably, the late-maturing cultivars exhibited significantly higher levels of CIR. Moreover, cultivars characterized as having high CIR exhibited potential for the development of adventitious roots (ARs) during callus induction, and a positive correlation was observed between CIR and the ability to regenerate ARs. However, long-term subculture callus lost root regeneration capacity due to changes in cellular morphology and starch and flavonoid content. Additionally, PpLBD1 was identified as a good candidate gene involved in the regulation of callus adventitious rooting in peach trees. Our results provide an insight into the mechanisms underlying callus induction and adventitious root development and will be helpful for developing regeneration systems in peach trees.

Expression quantitative trait loci mapping identified PtrXB38 as a key hub gene in adventitious root development in Populus.

Plant establishment requires the formation and development of an extensive root system with architecture modulated by complex genetic networks. Here, we report the identification of the PtrXB38 gene as an expression quantitative trait loci (eQTL) hotspot, mapped using 390 leaf and 444 xylem Populus trichocarpa transcriptomes. Among predicted targets of this trans-eQTL were genes involved in plant hormone responses and root development. Overexpression of PtrXB38 in Populus led to significant increases in callusing and formation of both stem-born roots and base-born adventitious roots. Omics studies revealed that genes and proteins controlling auxin transport and signaling were involved in PtrXB38-mediated adventitious root formation. Protein-protein interaction assays indicated that PtrXB38 interacts with components of endosomal sorting complexes required for transport machinery, implying that PtrXB38-regulated root development may be mediated by regulating endocytosis pathway. Taken together, this work identified a crucial root development regulator and sheds light on the discovery of other plant developmental regulators through combining eQTL mapping and omics approaches.

GWAS identifies candidate genes controlling adventitious rooting in Populus trichocarpa.

Adventitious rooting (AR) is critical to the propagation, breeding, and genetic engineering of trees. The capacity for plants to undergo this process is highly heritable and of a polygenic nature; however, the basis of its genetic variation is largely uncharacterized. To identify genetic regulators of AR, we performed a genome-wide association study (GWAS) using 1148 genotypes of Populus trichocarpa. GWASs are often limited by the abilities of researchers to collect precise phenotype data on a high-throughput scale; to help overcome this limitation, we developed a computer vision system to measure an array of traits related to adventitious root development in poplar, including temporal measures of lateral and basal root length and area. GWAS was performed using multiple methods and significance thresholds to handle non-normal phenotype statistics and to gain statistical power. These analyses yielded a total of 277 unique associations, suggesting that genes that control rooting include regulators of hormone signaling, cell division and structure, reactive oxygen species signaling, and other processes with known roles in root development. Numerous genes with uncharacterized functions and/or cryptic roles were also identified. These candidates provide targets for functional analysis, including physiological and epistatic analyses, to better characterize the complex polygenic regulation of AR.

ChIFNα regulates adventitious root development in Lotus japonicus via an auxin-mediated pathway

ABSTRACT Adventitious roots (ARs), developing from non-root tissue, play an important role in some plants. Here, the molecular mechanism of AR differentiation in Lotus japonicus L. (L. japonicus) with the transformed chicken interferon alpha gene (ChIFNα) encoding cytokine was studied. ChIFNα transgenic plants (TP) were identified by GUS staining, PCR, RT-PCR, and ELISA. Up to 0.175 μg/kg rChIFNα was detected in TP2 lines. Expressing rChIFNα promotes AR development by producing longer roots than controls. We found that the effect was enhanced with the auxin precursor IBA treatment in TP. IAA contents, POD, and PPO activities associated with auxin regulation were higher than wild type (WT) in TP and exogenous ChIFNα treatment plants. Transcriptome analysis revealed 48 auxin-related differentially expressed genes (DEGs) (FDR < 0.05), which expression levels were verified by RT-qPCR analysis. GO enrichment analysis of DEGs also highlighted the auxin pathway. Further analysis found that ChIFNα significantly enhanced auxin synthesis and signaling mainly with up-regulated genes of ALDH, and GH3. Our study reveals that ChIFNα can promote plant AR development by mediating auxin regulation. The findings help explore the role of ChIFNα cytokines and expand animal gene sources for the molecular breeding of growth regulation of forage plants.